As the oceans gradually become warmer and more acidified, an increasing number of studies test the effects of climate change on marine organisms. As most climate change experiments have studied effects of single climate variables on single species, more and more researchers ask themselves how this lack of realism affects our ability to accurately assess and predict effects of climate change (Wernberg et al. 2012). Interestingly, theory and a growing body of studies suggests that different climate variables can strongly interact (Kroeker et al. 2013), that climate effects can change with presence/absence of strong consumers (Alsterberg et al. 2013), and that effects on communities are more informative than those on single species, as they allow experimenters to assess what traits that makes organisms sensitive or resistant (Berg et al. 2010). In our new paper “Community-level effects of rapid experimental warming and consumer loss outweigh effects of rapid ocean acidification” we found that warming and simulated consumer loss in seagrass mesocosms both increased macrofauna diversity, largely by favoring epifaunal organisms with fast population growth and poor defenses against predators.

These results corroborate theory, and exemplify how trait- and life-history based approaches can be used to in more detail understand – and potentially predict – effects of climate change. Meanwhile, simulated ocean acidification (pH 7.75 vs. 8.10) had no detectable short-term effects on any of the investigated variables, including organisms with calcium-carbonate shell. While this lack of effect may be partly explained by the short duration of our experiment and/or the relatively crude endpoints, seagrass-associated macrofauna routinely experience diurnal pH variability that exceed predicted changes in mean pH over the coming century (Saderne et al. 2013). Consequently, by living in a variable pH these organisms could be relatively resilient to ocean acidification (see e.g. Frieder et al. 2014). In summary, it seems that at least in the short term, rapid warming and changes in consumer populations are likely to have considerably stronger effects than ocean acidification on macrofauna communities in shallow vegetated ecosystems.

References cited above:

Alsterberg, C., Eklöf, J. S., Gamfeldt, L., Havenhand, J. and Sundbäck, K. 2013. Consumers mediate the effects of experimental ocean acidification and warming on primary producers. – PNAS 110: 8603-8608.

Berg, M. P., Kiers, E. T., Driessen, G., van der Heijden, M., Kooi, B. W., Kuenen, F., Liefting, M., Verhoef, H. A. and Ellers, J. 2010. Adapt or disperse: understanding species persistence in a changing world. – Global Change Biol 16: 587-598.

Frieder, C. A., Gonzalez, J. P., Bockmon, E. E., Navarro, M. O. and Levin, L. A. 2014. Can variable pH and low oxygen moderate ocean acidification outcomes for mussel larvae? – 20: 754-764.

Kroeker, K. J., Kordas, R. L., Crim, R., Hendriks, I. E., Ramajo, L., Singh, G. S., Duarte, C. M. and Gattuso, J.-P. 2013. Impacts of ocean acidification on marine organisms: quantifying sensitivities and interaction with warming. – Glob. Change Biol. 19: 1884-1896.

Saderne, V., Fietzek, P. and Herman, P. M. J. 2013. Extreme Variations of pCO₂ and pH in a Macrophyte Meadow of the Baltic Sea in Summer: Evidence of the Effect of Photosynthesis and Local Upwelling. – PloS ONE 8: e62689.

Wernberg, T., Smale, D. A. and Thomsen, M. S. 2012. A decade of climate change experiments on marine organisms: procedures, patterns and problems. – Glob. Change Biol. 18: 1491-1498.

 

As the oceans gradually become warmer and more acidified, an increasing number of studies test the effects of climate change on marine organisms. As most climate change experiments have studied effects of single climate variables on single species, more and more researchers ask themselves how this lack of realism affects our ability to accurately assess and predict effects of climate change (Wernberg et al. 2012). Interestingly, theory and a growing body of studies suggests that different climate variables can strongly interact (Kroeker et al. 2013), that climate effects can change with presence/absence of strong consumers (Alsterberg et al. 2013), and that effects on communities are more informative than those on single species, as they allow experimenters to assess what traits that makes organisms sensitive or resistant (Berg et al. 2010). In our new paper “Community-level effects of rapid experimental warming and consumer loss outweigh effects of rapid ocean acidification“ we found that warming and simulated consumer loss in seagrass mesocosms both increased macrofauna diversity, largely by favoring epifaunal organisms with fast population growth and poor defenses against predators.

These results corroborate theory, and exemplify how trait- and life-history based approaches can be used to in more detail understand – and potentially predict – effects of climate change. Meanwhile, simulated ocean acidification (pH 7.75 vs. 8.10) had no detectable short-term effects on any of the investigated variables, including organisms with calcium-carbonate shell. While this lack of effect may be partly explained by the short duration of our experiment and/or the relatively crude endpoints, seagrass-associated macrofauna routinely experience diurnal pH variability that exceed predicted changes in mean pH over the coming century (Saderne et al. 2013). Consequently, by living in a variable pH these organisms could be relatively resilient to ocean acidification (see e.g. Frieder et al. 2014). In summary, it seems that at least in the short term, rapid warming and changes in consumer populations are likely to have considerably stronger effects than ocean acidification on macrofauna communities in shallow vegetated ecosystems.

 

References cited above:

Alsterberg, C., Eklöf, J. S., Gamfeldt, L., Havenhand, J. and Sundbäck, K. 2013. Consumers mediate the effects of experimental ocean acidification and warming on primary producers. – PNAS 110: 8603-8608.

Berg, M. P., Kiers, E. T., Driessen, G., van der Heijden, M., Kooi, B. W., Kuenen, F., Liefting, M., Verhoef, H. A. and Ellers, J. 2010. Adapt or disperse: understanding species persistence in a changing world. – Global Change Biol 16: 587-598.

Frieder, C. A., Gonzalez, J. P., Bockmon, E. E., Navarro, M. O. and Levin, L. A. 2014. Can variable pH and low oxygen moderate ocean acidification outcomes for mussel larvae? – 20: 754-764.

Kroeker, K. J., Kordas, R. L., Crim, R., Hendriks, I. E., Ramajo, L., Singh, G. S., Duarte, C. M. and Gattuso, J.-P. 2013. Impacts of ocean acidification on marine organisms: quantifying sensitivities and interaction with warming. – Glob. Change Biol. 19: 1884-1896.

Saderne, V., Fietzek, P. and Herman, P. M. J. 2013. Extreme Variations of pCO₂ and pH in a Macrophyte Meadow of the Baltic Sea in Summer: Evidence of the Effect of Photosynthesis and Local Upwelling. – PloS ONE 8: e62689.

Wernberg, T., Smale, D. A. and Thomsen, M. S. 2012. A decade of climate change experiments on marine organisms: procedures, patterns and problems. – Glob. Change Biol. 18: 1491-1498.

 

Understanding how changes in the climate affect biological communities is essential in predicting the future size and composition of populations. However, accurate predictions pose a difficult challenge for researchers. For the majority of animal species it is not feasible or ethical to conduct experiments into how these populations will respond to a changing climate. To enable us to gain an insight into potential futures of a population under climatic change, we use a computational model. Specifically, we use an integral projection model to investigate how changes in the North Atlantic Oscillation will influence the body weight and population size of a population of Soay sheep. The North Atlantic Oscillation is a large scale weather pattern of temperature differences across the Atlantic Ocean, which alters the local weather patterns in the North Atlantic region. We used published predictions of the future values of the North Atlantic Oscillation for the 21^st Century. By doing this we are able to project the response of the study population to climate change based on our current best projections of the future climate.

Our model results, presented in the Early View paper “Analysis of phenotypic change in relation to climatic drivers in a population of Soay sheep”,  suggest that a continued positive trend in the North Atlantic Oscillation (positive pressure difference between Iceland and the Azores), as predicted by the majority of models, will be accompanied by a decrease in the population size of the Soay sheep and an increase in mean body weight. These changes are likely caused by a loss of smaller individuals from the population due to higher mortality in the adverse winters (mild but wet and windy) associated with the positive North Atlantic Oscillation.

Using an integral projection model as we have in this study gives us a glimpse into the potential future of populations where experimentation is difficult, and can improve our understanding of how populations will respond to changing climatic conditions. Using published climate predictions within our model also allows such studies to be placed in the realm of current climate research and (importantly) our projections can be updated as new climate predictions are released.

This is our first collaboration study between a population geneticist, Hideki Innan, and a field-based tropical ecologist, me, Yayoi Takeuchi.
I have been long wondering why Hubbell’s neutral model fitted so well to tropical forest communities because my impression of the tropical forest was the opposite. When I was doing my postdoctoral work in Hideki’s lab, he got interested in this issue because Hubbell’s model is based on the theory of population genetics. As such we started working together on this topic, and I found that population genetics holds sophisticated and well-established theories and methodologies, which could be well applied to community ecology. We believe that incorporating those techniques will provide breakthrough insights to elucidate mechanisms shaping complex natural communities.

A species-rich tropical rain forest in Lambir Hills National Park in Sarawak, Malaysia. Photo by Yayoi Takeuchi

The study “Evaluating the performance of neutrality tests of a local community using a niche-structured simulation model” summarized:

Is your favorite local community really neutral? —- It might be “No”! Here, we found that two common methods to test Hubbell’s neutral model were not robust enough to reject neutrality.
Hubbell’s neutral model provides a good fit to the data from wide range of natural communities including tropical forests and coral reefs. There are two parameters in his model that are usually unknown and commonly estimated from the data to be tested. Two common methods to test Hubbell’s neutral model, the SAD-fitting approach and re-sampling approach, use these estimated parameters. To examine the performance of these tests, we developed a simple niche model which incorporates stochastic demography, and these two tests were applied to a simulated non-neutral data with niche-structured community. Our results suggested that these tests had relatively poor power to reject neutrality, simply due to overfitting of the neutral model with unrealistic estimated parameters. We also discussed how we could improve the performance in this paper.

The introduction of a new species to an ecological community can initiate a chain of events that results in a significant change to the community’s composition. For instance, the introduction of a pollinator species can facilitate the colonization of new plants that rely on the new pollinator for reproduction. Conversely, a pollinator species may drive down the population levels of certain species—e.g., if it aggressively robs a plant of its nectar without pollinating it.

How do communities respond to these invasions, and what lessons can be learned about the underlying properties of ecological communities in response to such invasions? In “Plant-pollinator community network response to species invasions depends on both invader and community characteristics,” the authors investigate the relationships between invasive species and community characteristics in shaping a plant-pollinator community’s response to an invasion.

Monarch butterfly (Danaus plexippus) on invasive plumeless thistle (Carduus acanthoides). Photo credit: Laura Russo

The study makes use of a computational model that was originally used to investigate the process by which stable plant-pollinator communities form. The use of such models is attractive for two main reasons. First, a model that recapitulates real-world behavior offers insight into the mechanisms that operate in nature; second, computational models allow rapid and widespread exploration that would be time-consuming, costly, and in some cases impractical to perform in nature. As such, computational models are well-positioned to speed up the process of scientific discovery by providing novel and informative predictions and insights into the properties of the systems being modeled.

The model itself is used to generate simulated plant-pollinator communities with properties drawn from the empirical literature. Interactions may be true mutualisms (beneficial to both species) or detrimental to one species and beneficial to another (e.g., insects that visit flowers for nectar without pollinating the plant and plants that trick pollinators without providing them with nectar rewards). Colonization or maintenance of a species in the community is possible if its beneficial interactions outweigh its detrimental interactions; otherwise, the species goes extinct.

The model predicts that invasive species with properties that are very different from the native species in the region (e.g., supergeneralists that benefit the species with which they interact) are more likely to drive significant changes in the number of species colonizing the community. When an invasive species increases the species richness of the invaded community, there is a corresponding increase in the community’s nestedness and a decrease in the community’s connectance. Nestedness is a measure that accounts for the tendency of the community to be composed of (1) generalist species that interact with many species and (2) specialist species that interact with a subset of generalists. Connectance is the number of observed interactions relative to the number of possible interactions. This predicted divergence in nestedness and connectance is in agreement

with recent empirical work, and stands in contrast to the correlation of these two measures when considering the process by which communities stabilize.

This finding is relevant to the active discussion among researchers concerning the relationship between nestedness and connectance. By investigating the differing behavior of these properties in the context of species invasion, this paper supports the argument that nestedness and connectance are complementary properties that provide a more accurate picture of a community together than either measure provides alone. These findings are most strongly supported in the context of invaders that increase the number of species colonizing the community. As these invaders tend to participate in many species-species interactions, this paper also highlights the important role of generalist species in shaping the structure and dynamics of ecological communities.

Despite the increasing use of Species Distribution Models (SDM) for predicting current or future animal distribution, only a few studies have linked the gradient of habitat suitability to demographic parameters.

Species Distribution Models are a niche modelling framework based on a statistical approach linking spatial data on the presence/absence of species to predictive environmental variables. Because they do not account for demographic and ecological processes that may constrain responses to environmental factors at a population level, the projections of SDM cannot be used directly to predict the associated extinction risk. In this context, approaches accounting for mechanistic processes directly linked with extinction across distribution ranges are considered as promising steps to better understand and predict the response of species to environmental change. While such approaches can improve the reliability of models, empirical works are essential to further develop our understanding of processes underlying distribution patterns and potentially develop better SDM that could integrate factors driving species distribution and persistence. Moreover, the adequacy of projections with demographic parameters is a critical issue when they have to be applied for conservation planning.

In our study “Evidence of a link between demographic rates and species habitat suitability from post release movements in a reinforced bird population” just published in Oikos, we tested whether the spatial variation in habitat suitability along the individual movement path is related to survival.

Radio-tracking of North African Houbara Bustard in Eastern Morocco

We used an extensive tracking data collected from captive-born individuals translocated to reinforce the wild populations of Houbara bustard (Chlamydotis undulata undulata). This translocation program provides an ideal study framework including information on the spatial distribution of wild-born individuals and intensive individual-based monitoring of captive-bred released individuals.

We first modelled and mapped the habitat suitability from presence data of wild individuals using niche models in a consensus framework (BIOMOD platform). We further analysed survival of 957 released individuals using capture-recapture modelling and its links to habitat suitability, as the trend in suitability from the release sites along movements.

North African Houbara Bustard (Chlamydotis undulata undulata)

We found that the survival of released individuals was related to changes in habitat suitability along their movements. For instance, individuals which moved to sites of lower habitat suitability than their release sites have lower survival probabilities than the others, independently of the habitat suitability of the release sites and daily movement rate. Interestingly, the most positive changes in habitat suitability were not characterized by highest survival probabilities, likely due to density-dependant processes.

We provide an empirical support of the relationship between habitat suitability and survival, a major fitness component. These results illustrate the relevance of linking demographic processes with Species Distribution models, but also underline the importance of other mechanisms acting on demographic parameters and possibly mitigating such relationship (social organisation, density dependence).

The authors through Anne-Christine Monnet

 

Everyone who likes to spend some time in nature, or who has trees at home, knows that several animals love to feed on fruits. Figs, tomatoes, peppers, guavas, mangos, bananas, and many other delicacies are harvested by frugivores that range from tiny bats to huge elephants.

Those animals render the plants a service known as seed dispersal: in other words, they carry their seeds away and so increase the chances of their offspring surviving attacks by natural enemies, establishing, and colonizing new sites. This myriad of interactions forms a tangled web of frugivores and fruits, which is vital to maintain and regenerate forests and other natural ecosystems. Some frugivores seem to be more important than others to keep those webs functioning. In our study “Keystone species in seed dispersal networks are mainly determined by dietary specialization”, focused on bats and birds, the main groups of seed dispersers in the Neotropics, we found out that, even though animals with other kinds of primary diets participate in seed dispersal networks, specialized frugivores are the keystones of those systems and hold them together. This finding may help plan for the conservation and restoration of seed dispersal in degraded areas, and also provide insights on how to accelerate the regeneration of tropical rainforests and savannas.

Marco A.R. Mello and co-authors

Experimental warming is an effective approach to determine the effect of increasing temperature on ecological processes, with few confounding factors (e.g., other variables that covary spatially and temporally with temperature). Therefore, a number of field experiments have been initiated worldwide to study the effects of simulated global warming. A wide range of techniques (e.g., greenhouses, open-top chambers, and electric infrared heaters) have been developed to experimentally warm a variety of small plants, including those of the tundra, grasslands, and sapling trees. Within forests, most insect species diversity and plant-insect interactions are concentrated in the canopy of mature trees, rather than in the understory, because of higher plant productivity. However, few studies have examined the responses of mature trees to experimental warming in natural forests.

In the paper “Different initial responses of the canopy herbivory rate in mature oak trees to experimental soil and branch warming in a soil-freezing area”, we report the initial 3-year (2007–2009) results of an experimental warming of mature Quercus crispula (18–20 m in height), a late-successional tree species. Five mature Q. crispula trees whose canopy was accessible by a gondola hanging from a construction crane were selected (Photo1). To better understand the mechanism by which global warming affects plant-insect interactions in the canopy of mature oak trees, field experiments must warm aboveground and belowground regions separately. Thus, we experimentally increased the temperature of the surrounding soil and canopy branches of mature oak trees by approximately 5°C using electric heating cables (Photo 2 and 3).

Our warming experiment clearly demonstrates that plant-insect interactions in the canopy responded differently to soil and branch warming of mature oak trees. Soil warming in a mature cool-temperate forest with a freeze-thaw cycle decreased the nutritional quality of leaves and the rate of herbivory in the canopy, whereas branch warming had no effect on canopy leaf traits or the herbivory rate. The magnitude of the indirect (plant-mediated) effects of belowground temperature elevation on canopy herbivory was gradually enhanced during the initial 3 years of the study. These results suggest that belowground temperature elevation due to global warming in a soil freezing area is an important driving force of plant-insect interactions in the canopy. For a better understanding of the mechanism by which global warming affects plant-insect interactions in mature cool-temperate forests, this warming experiment should be continued using mature oak trees because indirect effects of temperature are likely more pronounced in the long- than in the short-term.

Masahiro Nakamura and co-workers

Elevational gradients have become important tools for assessing the effects of temperature changes on vegetation properties, because these gradients enable temperature effects to be considered over larger spatial and temporal scales than is possible through conventional experiments. During the summer of 2012, we collected soils along an elevational gradient on Mount Suorooaivi near Abisko, Sweden for two growth chamber experiments to determine the effects of temperature, soil origin (proxy for soil legacy) and vegetation type on the growth responses of two grass species. The results are published in the Oikos paper “Plant growth response to direct and indirect temperature effects varies by vegetation type and elevation in a subarctic tundra”. 

Soils were collected at each of three elevations from each of two vegetation types, specifically heath, dominated by dwarf shrubs, and meadow, dominated by graminoids and herbs. Plants responded to both the direct effect of temperature and its indirect effect via soil legacies, and that direct and indirect effects were largely decoupled. Vegetation type was a major driver of plant response; responses to soils from increasing elevation were stronger and seedlings showed a more linear decline in biomass when grown in meadow as opposed to heath soils.

The effect of soil biota on plant growth was independent of elevation, with a positive influence across all elevations regardless of soil origin for meadow soils but not for heath soils. Collectively, the responses of plant growth to soil legacy effects of temperature across the elevational gradient were driven primarily by soil abiotic, and not biotic, factors. These findings demonstrate vegetation type is a strong determinant of how temperature variation across elevational gradients impacts on plant growth, and highlight the need for investigating both direct and indirect effects of temperature on plant responses to future climate change.

 

Jonathan de Long and co-workers

Biotic interactions play a central role in determining species distribution and abundance. Indeed, some organisms can have particularly strong effects on the distribution of other species because they act as keystone species or ecosystem engineers whose effects cascade to other trophic levels – beavers are one well-known example of this. In coffee agroecosystems in Southern Mexico we studied how a keystone species, the dominant arboreal ant A. sericeasur, influences the distribution and abundance of Pocobletus sp. nova, tiny spiders that spin their webs in coffee plants (Fig. 1 and Fig. 2). The results are now published Early View in Oikos in the paper “A positive association between ants and spiders and potential mechanisms driving the pattern”

 

Figure 1. Pocobletus sp. nova on a coffee bush. Notice the hammock web; the white little balls are Pocobletus ovisacs

 

 

Figure 2. Close up of a female of Pocobletus sp. and its spiderlings. Ovisacs in the background.

 

The first thing that we noticed when sampling spiders in coffee plants was that Pocobletus spiders tended to be very abundant in the presence of A. sericeasur. So we asked ourselves, why are these tiny spiders associated with these ants? To what extent do the dominant A. sericeasur ants influence the spatial distribution of Pocobletus?

 

In the summer of 2010, we set up four plots around shade trees that had A. sericeasur nests in Finca Irlanda, a coffee farm in Chiapas, Mexico (Fig. 3). In each plot we assigned a unique number to each coffee plant, recorded which coffee plants were patrolled by A. sericeasur or other ants, and sampled spiders. We also sampled the webs of Pocobletus in coffee plants that were and were not patrolled by A. sericeasur.

 

Figure 3. At finca Irlanda, before sampling spiders.

 

We were very excited by our results. We discovered that the spatial distribution of Pocobletus spiders is indeed strongly associated with A. sericeasur. In addition, we found that the webs of Pocobletus spiders have more prey items in the presence of A. sericeasur than in its absence.

Figure 4. Pocobletus sp. and its predators. Notice the small Pocobletus in the lower section of the web and the slightly bigger Argyrodinae spider in the upper part.

 

We were also very surprised to discover that Pocobletus spiders have a wide variety of predators, and that these predators are other spiders! (Fig. 4). But we were even more surprised when we found out that the abundance of these predators decreases in the presence of A. sericeasur. So, contrary to what you might expect, a coffee plant full of bustling A. sericeasur ants can be a great place for a tiny spider to be, with plenty of food and fewer enemies. If you want to know more about this research, read our paper to find out the whole fascinating story!

Linda marin and co-authors

I hope you haven’t missed that Oikos from 2015 changes cover each month! The photo for each issue is from one of the papers. The January cover photo was taken by David W. Inouye. The paper in questions is “Phenological shifts and the fate of mutualisms” by Nicole Rafferty and co-workers.

Here’s David’s description of the photo:

A male Broadtailed Hummingbird (Selasphorus platycercus) visiting a flower of dwarf larkspur (Delphinium nuttallianum) near the Rocky Mountain Biological Laboratory, Gothic, Colorado, USA. The hummingbirds are common at this site, and the larkspur flowers can carpet meadows early in the summer; they are an important nectar source for the birds at the beginning of the breeding season. The male hummingbirds have a slot between their first two primary feathers (visible in the photo), which makes a loud trilling noise as they fly. Nikon D200e camera with a Nikkor 70-200mm lens at 155mm, Nikon R1 flash, iso 250, 1/250 sec, f20.

Herbivory may be changed by climate change and how does that affect the host plants? Find out in the Early View paper “Colonization of a host tree by herbivorous insects under a changing climate” by Kaisa Heimonen and co-workers. Below is their summary of the paper: Climate warming is predicted to increase the abundance of herbivorous insects due to increased survival, growth and multivoltinism. In addition, due to warming climate many insect species are predicted to shift their ranges to higher latitudes. Host plants are adapted to the present day herbivore pressure and insect communities but in the future the abundance of insects and the composition of herbivorous insect communities might change which can lead to more intense herbivore damage. We wanted to study the susceptibility of silver birch (Betula pendula Roth) populations from different latitudes to the insect herbivores that are expected to spread northwards in the future. To do this we established three common gardens with 26 genotypes of silver birch from six latitudinal populations in Finland ranging from 60°N to 67°N. The common gardens were located at three different latitudes 60°N, 62°N and 67°N. At each study site 260 silver birches were growing. This experimental setup is being used also for several other studies (see the project homepage: http://www.uef.fi/fi/birchadaption).

Figure 1. Map showing the three common garden sites (filled squares) and the six source populations (filled circles). Mean annual temperature isoclines are shown in grey.

Figure 2. The three common garden sites in Finland where the study was conducted. A) Southern study site is located in Tuusula 60°N, B) Central study site is located in Joensuu 62°N and C) Northern study site is located in Kolari 67°N. Photo credits: Kaisa Heimonen.

We wanted to study how the local insects at each of the common garden sites colonized the translocated birch genotypes. We asked if the insect herbivore density, species richness or community composition could be explained by the source population of the birch or by the direction or distance of the latitudinal translocation. The herbivore community on the study birches was examined during two growing seasons in 2011 and in 2012.

Figure 3. Kaisa Heimonen (lead author) observing the herbivorous insects on silver birch at the northern study site in 2012. Photo credits: Sari Kontunen-Soppela.

Herbivore density among the source populations differed in 2012 but not in 2011 and species richness was not affected by the source population. Latitudinal translocation could not explain the variation in the herbivore density or in the species richness. Community composition of the herbivores differed among the source populations at two of the three study sites and the similarity of the herbivore communities decreased with increasing latitudinal distance of the source populations.

Figure 4. Common insect species on silver birch belonging to the orders Lepidoptera, Coleoptera and Hymenoptera. A) White-shouldered smudge (Ypsolopha parenthesella), B) Birch leaf roller (Deporaus betulae) and C) Early birch leaf edgeminer (Fenusella nana). Photo credits: Kaisa Heimonen.

Silver birch genotypes from source populations originating from closer geographical distance had more similar herbivore community composition at our experimental sites possibly because they are genetically more similar than the geographically more distant birch genotypes. All birch genotypes were colonized by some of the local herbivores at all three study sites suggesting that in the future herbivorous insects are able to colonize novel host plant genotypes. The results of this study show that compositional changes in the insect communities on their host plants are expected in the future. Newly structured herbivore communities might affect the herbivore damage and thereby also the plant growth.

 

Fig. 1. Recently metamorphosed green frog (Lithobates clamitans) at the edge of a pond (photo by Laura Martin)

 

Fig. 2 American toad (Anaxyrus (Bufo) americanus) adult (photo by Carrie Brown-Lima) American

 

Amphibians develop in watery places that are full of plants. And yet we know little about how these plants affect larval amphibians. As disease, climate change, and land-use change continue to threaten amphibian populations worldwide, it is more important than ever to understand what makes for good amphibian habitat.

 

 

Fig. 3 Shauna-kay Rainford at Bear Swamp, NY, one of the litter collection locations(photo by Laura Martin)

 

In the study “Effects of plant litter diversity, species, origin and traits on larval toad performance,” Cornell undergraduate Shauna-kay Rainford (now a graduate student at Penn State University), graduate student Laura Martin, and Professor Bernd Blossey investigated how plant litter communities influence the growth and survival of Anaxyrus americanus (American toad) larvae. They reared tadpoles in singles species and litter mixtures using 15 native and 9 nonnative plant species common to central New York, USA, recording survival, time to metamorphosis, and growth rate.

 

 

Fig. 4 Microcosms in which individual larval amphibians were reared in leaf litter treatments. (photo by Shauna-kay Rainford)

 

Survival in single species treatments ranged from 0% (in Rhamnus cathartica litter) to 96% (Pinus strobus). Tadpoles also failed to metamorphose in Acer rubrum, Cornus racemosa, Rosa multiflora, and Tsuga canadensis. Percent metamorphosis was highest in nonnative Lonicera spp. (76.7%), native Phragmites australis americanus (73.3%), nonnative P. australis (60.0%), and nonnative Alnus glutinosa (60.0%). Interestingly, whether the plant was native or nonnative did not affect amphibian performance.

In multi-species treatments, number of plant species had no effect on larval survival or metamorphosis. However, larvae reared in mixtures of 3 species were larger than those reared in single species treatments of the same species. But increasing litter diversity to 6 or 12 species did not further improve larval survival or performance. This result is consistent with analyses that reveal that most ecological processes saturate at relatively low levels of diversity.

Currently, understanding of the relationships of biodiversity and ecosystem function is drawn largely from studies of plant communities in temperate grassland ecosystems. But the vast majority of plant material is not consumed green; it enters detrital food webs like the one studied in this experiment. This study is an important first step towards understanding the mechanisms that underlie plant-amphibian interactions. It further highlights the importance of plant traits, but not origin, when considering amphibian habitat restoration and conservation.

Invasive species have negative economic and environmental consequences worldwide and, in our changing world, it has become increasingly important to understand their impacts. However, when assessing the impacts of invasive species, scientists often compare un-invaded sites with highly invaded sites, representing the ‘worst-case scenario’. Consequently, there is little information on how the impact of invaders varies with their population size. In the Early View paper “Population density modifies the ecological impacts of invasive species” we use experimental ponds to assess how ecological impact varies across different population densities for a model invasive fish (Pseudorasbora parva).

We examined the relationship between density and impact to develop density-impact curves (see attached figure). We found both linear and non-linear density-impact curves for different direct and indirect ecological impacts. For instance, the relationship between fish density and zooplankton biomass and abundance was a high-threshold curve, indicating a smaller impact than a linear relationship would predict.

We also found density-impact relationships that were linear, low-threshold or s-shaped. Therefore, we caution against
the common assumption that ecological impact increases linearly with invader density. An understanding of the relationship between invader population density and ecological impact can assist in developing realistic and sustainable management strategies for controlling the negative impacts of invaders.

The potential relationships between invasive population density and
ecological impacts. Re-drawn from Yokomizo et al. (2009, Ecological
Applications; DOI:10.1890/08-0442.1).

Michelle C. Jackson and co-authors

Do migratory birds catch more parasites? This is explored in the Oikos Early View paper “Flying with diverse passengers: greater richness of parasitic nematodes in migratory birds” by Janet Koprivnikar and tommy L.F. Leung. Below is their short summary of the study:

Many different animals undergo annual migrations and some of them cover enormous distances with their journey. This undertaking can be extremely strenuous and physiologically demanding. Aside from the demands of the journey itself, most animals don’t travel alone – they carry with them an entire community of different parasites throughout their body. Migratory birds undergo annual migratory flights across the globe and birds are well known to be a haven for
pathogens. Most birds are infected with dozens of different species of parasite, many of them worms of all shapes and sizes. While most studies looking at bird parasites in relation to their ecology or migratory habits have focused on blood-dwelling types such as avian malaria, few have studied their worms despite the relative abundance of these parasites in their hosts. Of those different types of worms, the most harmful are the nematodes (roundworms). Some nematodes can cause serious diseases in birds so we decided to compare the diversity of parasitic roundworms in migratory birds versus that of non-migratory species.

In particular, we focused our attention on three orders of birds; water birds (Anseriformes), perching birds (Passeriformes), and birds of prey (Accipitriformes). We found that for any of those given orders, the migratory species tended to have a wider range of roundworms than non-migratory species. Furthermore, we also found that bird species which have proportionally larger spleens also happen to have a greater variety of roundworms infecting them.

Fig. 1: A migratory bird species (Anas platyrhynchos – the mallard duck) reported as a host for 69 different species of roundworm.

Fig. 2: Mean nematode species richness (corrected for host study effort) + S.E. for migratory and resident bird species in the Anseriformes, Accipitriformes, and Turdidae (N = 188).

So why do migratory species have more diverse nematode communities than their non-migratory relatives? We don’t know that at this point. It is possible that migratory birds pick up many different species of parasites during their journey whereas non-migratory species which stick to a single location their entire life are exposed to a more limited range of parasites. Or perhaps because migration is such a stressful exercise, migratory birds can become stressed during such journeys and become more vulnerable to a wider variety of parasites. Or it might be both!
Due to the diseases that parasitic roundworms can cause in birds, it is important to also keep them in mind when considering the effects that global perturbations such as climate change can have on the ecology of migratory species. As migratory birds change their arrival and departure timing, and are also forced to alter their migratory routes and stopover sites, they might become more stressed and susceptible to parasitism. Furthermore, altered migratory routes and stopover sites can also mean that migratory birds might be introducing their rich suite of worms to new areas and potential hosts.

Moving to a new site for next brood? Good or bad? And why? These questions are answered in the Early View paper “Mechanisms and reproductive consequences of breeding dispersal in a specialist predator under temporally varying food conditions” by Julien Terraube and co-workers.

In this study, we explored the factors linked to variations in breeding dispersal behaviour and their consequences in terms of reproductive parameters in a raptor species. Which factors influence individual dispersal decisions? Are Eurasian kestrels Falco tinnunculus able to increase their own reproductive success after moving from one site to the other between two consecutive breeding seasons? Is this relationship mediated by environmental factors like food abundance or individual traits like gender or age? All these fascinating questions are hard to answer particularly in avian predators because of methodological limitations associated to size of the study area and even more in species like Eurasian kestrels breeding in boreal ecosystems, which have high breeding dispersal propensity and in which movements are driven by cyclic fluctuations in abundance of main foods (voles) (see Vasko et al. 2011).

In spring 1977, a long-term study of a local kestrel population breeding in western Finland (the Kauhava region) was initiated along with the monitoring of Tengmalm’s owl populations (see Korpimäki and Hakkarainen 2012). Hard work in the field has generated a fantastic long-term, large-scale dataset combining data from breeding success and individual traits of breeding kestrel parents captured at their nest sites over the last 25 years (1983-2013).

 

A +1-year old male kestrel on hand after trapping. Photo: Erkki Korpimäki.

Given the increasing demand for long-term population studies in order to understand current impact of environmental changes, the authors would like to stress the importance of long-term studies on demographic parameters in long-lived vertebrate populations. In this study, the assessment of breeding dispersal distances was made possible through systematic capture of most kestrel parents breeding in the main study areas, ringing and recovery of previous rings. We would like to focus here on the capture procedure that allowed collecting breeding dispersal data and share the experience acquired during the hours spent in “Wild-West” of Finland when checking traps.

 

Three-week old nestlings in the nest-box. Photo: Erkki Korpimäki

Capture occurs during the brood-rearing period when chicks are two-to-three weeks old, in order to avoid unnecessary disturbance of young nestlings during the most vulnerable phase. Virtually all the breeding population monitored breeds in nest-boxes that were set up on barns from early 1980s onwards. The total number of nest-boxes has varied from 350 to 450 throughout the study period in agricultural fields of the study area. We have used swing-door traps attached to the front of the nest box for trapping parents. The “trapping routine” starts by erecting the traps early in the morning from 5-6 am on a group of 5 to 10 breeding sites selected according to nestling age. Then trap-checking rounds are performed every two-to-three hours to check if any individual is trapped. The aim is to capture both female and male from each breeding site within 12 hours. Adults are ringed, measured and weighed near the breeding site and released as soon as possible. A capture day ends by giving newly-hatched rooster chickens to the kestrel nestlings to compensate for the decrease in prey delivery rates experienced during the trapping of their parents.

We have been lucky in the sense that voluntary birdwatchers and ringers have set up many large nest-box networks for kestrels in surrounding areas in western Finland. In addition, many voluntary ringers, particularly Erkki Rautiainen and Jussi Ryssy, have also made huge efforts to trap and ring kestrel parents and to ring fledglings at these nest-boxes.

A female kestrel with metal and colour rings in the front of the nest-box. Photo: Benjam Pöntinen.

A total of 2089 males and 2544 females were trapped at nests during 1985 to 2011 in our study areas. Trapping success remained relatively constant over the period: of all the nesting attempts on average 70% of the male and 80% of the female parents were successfully captured yearly. This large-scale trapping and ringing program allowed us to collect 631 dispersal events from 1985 to 2011 that were analysed in this study.

Overall, we found that females dispersed further than males and older individuals dispersed further than yearlings. A noteworthy aspect of this study involved the evidence of body-condition dependent dispersal strategies in kestrels as the individual body condition index was positively correlated to breeding dispersal distances, particularly in females. Strikingly, our results also evidenced complex patterns of non-linear relationship between previous breeding success and dispersal distances. Finally, longer dispersal distances were associated with reproductive costs in males under increasing vole abundance, whereas those females dispersing further increased their breeding success under all conditions of food abundance.

These results call for further research as clearly there is more to learn about the link between potential pre- and post-breeding prospecting movements, optimal dispersal decisions and population dynamics in avian predators inhabiting fast changing boreal ecosystems.

 

References

 

Korpimäki, E. & Hakkarainen, H. 2012. The boreal owl: Ecology, Behaviour and Conservation of a Forest-Dwelling Predator. – Cambridge University Press, Cambridge. 372 pages.

 

Vasko, V., Laaksonen, T., Valkama, J. & Korpimäki, E. 2011. Breeding dispersal of Eurasian kestrels (Falco tinnunculus) under temporally fluctuating food abundance. – Journal of Avian Biology 42: 552-563. (doi: 10.1111/j.1600-048X.2011.05351.x)

Timing is everything. For an interaction to take place, organisms not only have to be at the same place, they need to be there at the same time. The timing of flowering has likely been an important trait ever since the first flowers appeared on Earth ~200 million years ago; and when the climate changes, phenological changes belong to the most striking ecological responses. The timing of biological events is an important and exciting phenomenon in life-history evolution.

There is currently widespread concern that climate-driven changes in the timing of seasonal events may disrupt important ecological interactions such as pollination or cause temporal mismatches between critical periods in animal life-cycles and food availability. Phenological change has received substantial attention and has also been treated in thematic issues in other journals. This thematic issue of Oikos, however, has a more specific focus on the interplay between phenology and ecological interactions and on understanding phenological change from the perspective of life-history evolution. The articles, contributed by ecologists with expertise in phenology and/or theoretical ecology represent a wide range of scientific approaches. The volume contains theoretical investigations emphasizing the role of phenology in meta-community networks (Revilla et al.), in evolutionary games (Day and Kokko, Schmidt et al.) and in density-dependent population dynamics (Reed et al.). It also contains field studies of timing of reproduction in species adapting o climate change (Bennet et al., Van Dyck et al.) and experiments showing how timing of germination influences interspecific competition among plants (Cleland et al.). Among the contributions are furthermore reviews and conceptual papers on phenological change in the context of plant-pollinator interactions (Forrest), mutualisms in general (Rafferty et al. ) and plant life histories (Ehrlén) along with a synthesis of theory emerging in this field (Johansson et al.).

Phenological data continues to accumulate in ongoing, large-scale monitoring programs and we have increasingly refined methods to monitor changes. However, so far our knowledge has to a large extent been descriptive and any explanations for observed phenology patterns have been proximate and focused on abiotic influences. This special issue deals with how ecological interactions influences phenological patterns and vice versa. Some of the contributions have also provided ultimate explanations to phenological processes and patterns. That way, this issue offers a novel take on an old research topic and it provides a snap shot of the latest developments in this exciting research area.

Jacob Johansson, Jan-Åke Nilsson and Niclas Jonzén, editors of Oikos issue “Phenological change and ecological interactions”

We are very happy to welcome Dr. Francois Massol to Oikos Editorial Board. Get to know him here:

What’s your main research focus at the moment?

These days, I try and focus my efforts on the evolution of dispersal and the evolutionary ecology of interaction networks. What I want to understand is how some traits and some particular positions in ecological networks come to be associated with a given propensity to disperse. This issue is important from a fundamental viewpoint – it relates to the knowledge of so-called “dispersal syndromes” – but it is also a hot issue from a more applied perspective because it could help understand the evolutionary emergence of would-be invasive, keystone or easily threatened species. Given my personal bias towards equations and theory, I tend to first confront these issues using models and then collaborate with more empirically minded colleagues to test theoretical predictions with field or experimental data.

However, when I write “focus my efforts”, I have to acknowledge that I spend quite a significant fraction of my time away from my usual favourite subjects, working on interdisciplinary projects (mostly with social scientists and physicists) – and I am rather thankful for these little eccentricities, for they help me broaden my perspective of theoretical approaches to modelling the dynamics of biodiversity.

Can you describe you research career? Where, what, when?

Coming from a typically French undergrad background (maths and physics), I switched to ecology and evolutionary biology during my Master and then my PhD in Montpellier, under the supervision of Philippe Jarne at the CEFE. My work at that time was focused on community ecology models. After I graduated, my first position was at the Irstea Hydrobiology lab in Aix-en-Provence, to work on more functional aspects of aquatic communities. While I was employed at Irstea, I obtained a Marie Curie fellowship that allowed me to spend a year (2009 – 2010) in Mathew Leibold’s lab in Austin, Texas, where I tried to run a mesocosm experiment dealing with the effect of dispersal on the functioning of food webs (sadly, the experiment failed, but this is another story). In 2012, I was recruited at the CNRS in Montpellier (back to the CEFE), in the group of Pierre-Olivier Cheptou, to work on the evolution of mating systems and dispersal traits in plants. In 2013, I moved to a CNRS lab in Lille (GEPV) where I joined the group of Sylvain Billiard to work on the evolutionary ecology of mating systems. Moving so frequently is both a boon and a curse for obvious reasons, but as a connoisseur of the evolution of dispersal, I try to wear this as a badge of honour (and humour).

How come that you became a scientist in ecology?

If I were to explain why I became a scientist based on personality and motivations alone, curiosity together with the possibility of working in a free-thinking environment surely had a role at some point. I would also add that my personal kind of stubbornness probably helped a lot in getting me there. However, I think it’s also quite enlightening to think of a career path in science as built half on motivations and half on contingencies. The original contingency that set me on track was the first scientific internship I did back in 2002 in Dima Sherbakov’s lab at the Limnological Institute in Irkutsk, Russia. The atmosphere in the lab, the way people were working, the passion that permeated the place – all of this probably triggered something in my mind and I have been fond of this ambience ever since. The second set of happy contingencies have been the genial encounters I made afterwards when I was looking for a PhD project, i.e. Daniel Gerdeaux and Philippe Jarne, and then during my PhD (Pierre-Olivier Cheptou, to name but one person). I am convinced that a large part of my day-to-day satisfaction at work is based on the variety and the general goodwill of the colleagues with whom I interact.

What do you do when you’re not working?

At the moment, I am quite busy taking care of the house we just bought. House chores, family and friends occupy a consequent share of my non-lab time… Generally, I tend to spend the rest of my spare time reading (Terry Pratchett, Neal Stephenson, John Le Carré, Jasper Fforde and Neil Gaiman are always on top of the list), hiking, traveling and playing badminton.

Personal webpage: https://sites.google.com/a/polytechnique.org/francoismassol/home

ResearchGate page: https://www.researchgate.net/profile/Francois_Massol

 

The complicated predator-prey interactions are one of the most fascinating fields in ecology. They have been studied for decades, and the more we learn, the more surprising and unpredicted stories that we find. For me, finding that small rodents (lemmings) in the high Arctic may affect the populations of waders on the coast of Australia, New Zealand or South Africa was a real amazement.

Lemming populations have been known to show 3-5 years cycle, driven by either top-down or bottom-up control. In the Early View paper “Loss of periodicity in breeding success of waders links to changes in lemming cycles in Arctic ecosystems”, we have studied the interactions between the breeding success of high-Arctic nesting migratory shorebirds and lemming abundance, as they were suggested to be linked via the ‘alternative prey hypothesis’: In years of low lemming abundance, their predators, mainly Arctic fox, would switch to alternative prey, including chicks and eggs of shorebirds. In light of the large amount of evidence that lemming cycles have now changed and even disappeared in some parts of the Arctic, we found that the breeding success of these migrants used to follow the cycles of lemmings, but these cycles have too started to disappear, suggesting a cascading effect of changes in lemming cycles.

Siberian lemming © Pavel Tomkovich

The reason for these changes in lemming cycles is still not entirely known. One possible explanation is that climate change caused alteration of the snow structure which is a crucial hiding and feeding place for lemmings during winter. It might also be the natural tendency of populations in nature to go in and out of cycle. As shorebirds are known to consume considerable amount of benthic invertebrates, these changes in lemming cycle in the high Arctic potentially not only affect shorebird populations in the other side of the worlds, but also have a far-reaching cross-systems consequences on the ecosystem on the southern hemisphere.

 

Perfectly camouflaged shorebird chick with its ‘not so camouflaged’ parent, on the beautiful high Arctic breeding grounds © Pavel Tomkovich

 

Who will eat me and how fast will I be out-competed? Questions about the future for eucalyptus seedlings in a kangaroo world. Read more in Early View paper “Associational refuge in practice: can existing vegetation facilitate woodland restoration?” by Rebecca S. Stutz and co-workers. Below is their own summary of the study:

The characteristics of plant patches influence whether and how herbivores search for, detect and consume particular focal plants. Neighbouring plants may disrupt this foraging process at any phase, providing associational plant refuge for a focal plant. If we understand how and why this occurs, we may be able to improve revegetation efforts by planting strategically amongst existing vegetation to maximise their chances of escape from herbivory. We tested the capacity of existing vegetation in a degraded area of Booderee National Park, eastern Australia, to provide refuge for eucalypt seedlings from abundant mammalian herbivores. We quantified a suite of variables at large and small patch scales and used field cameras to confirm which herbivore species was responsible for seedling consumption.

Swamp wallabies were the principal browsers of seedlings. When they detected a seedling, they almost always decided to consume it, usually completely. At the larger patch scale, seedlings escaped browsing by swamp wallaby for longer in patches with fewer browsed plant species and those dominated by ferns rather than grasses. Higher understorey cover provided refuge for seedlings at the small patch scale. These characteristics are all consistent with disruption to the search and detection phases of the foraging process, and therefore the occurrence of associational plant effects. Lower canopy cover at the large scale also reduced browsing but the mechanism may be through its influence on microclimate, probability of finding seedlings below-canopy, or perceived predation risk. Our study demonstrates that existing patch characteristics can both provide associational plant refuge and influence patterns of herbivore foraging more generally.

Photos 1 & 2: Our focal seedling Eucalyptus pilularis before and after browsing by a swamp wallaby.

A swamp wallaby discovers a eucalypt seedling.

How species may cope with global warming is studied in the Early View paper “Geographic mosaics of phenology, host preference, adult size and microhabitat choice predict butterfly resilience to climate warming” by Nichole L. Bennett and coworkers. Below is their summary of the study:

Scientists investigating biological response to climate change have traditionally focused on how species move in space or in time to track the “climate envelope” (range of climatic conditions within which a species can survive). However, many species are able to buffer the effects of overall climate through habitat use. For example, the black-veined white butterfly, Aporia crataegi, achieves the same egg temperatures at both low and high elevations in Spain by laying eggs on the cool north-facing sides of host plant bushes at low elevation and on the warm south-facing side at higher altitudes¹. Our study organism, Edith’s checkerspot butterfly, Euphydryas editha is known to be climate-sensitive and associates with a variety of host plants. It also exhibits between-population variation in peak flight time, so this study system provides an excellent system to investigate the options available to a species with diverse habitat use and diverse seasonality in a warming world.

Suitable egg-laying site choice is critical to egg and caterpillar survival. Newly-hatched larvae do not travel far from the site where eggs were laid and normally begin feeding on the plant chosen by their mother or a nearby plant. Edith’s checkerspot feeds on plants in the families Plantaginaceae (Collinsia, Plantago, Penstemon) and Orobanchaceae (Pedicularis, Castilleja). Butterflies lay their eggs on their principal host plant in a complex spatial mosaic^2,3. Populations that feed only on Pedicularis and populations that feed only on Collinsia differ in a suite of adaptations^2,4,5. For instance, butterflies that are adapted to Pedicularis lay their eggs low on the plant while butterflies adapted to Collinsia lay their eggs higher up on the plant. We became interested in the consequences of host plant adaptation, especially egg-laying height, for the thermal environment of the eggs and newly-hatched larvae.

Butterflies adapted to Pedicularis lay their eggs low.

Butterflies adapted to Collinsia lay their eggs high.

To investigate whether egg-laying height influenced egg thermal environment, we measured heights of egg clutches, egg clutch temperature, and ambient temperature at eight field sites. No matter what plant was used, eggspace temperatures decreased with increasing egg height on plant, with hotter temperatures near the ground. To determine how much “wiggle room” these butterflies have for future warming, we asked if eggs could be laid at cooler microsites (i.e. higher) on the same plants. Eggs at seven of the sites were laid as low as possible, and there was only one population where the eggs were laid as high as possible on the plant. So, Edith’s checkerspot butterfly seems to retain options for buffering future warming with regard to host plant microclimate.

Populations of the butterfly also vary drastically in timing of peak flight season, and we were interested in the thermal consequences of this variation. Using a combination of observations and museum records⁶, we found that peak flight season varies between March and July. From the PRISM climate mapping system, we retrieved the mean daily maximum temperatures for each site (averaged over 1970-2000 in a 800m² grid)⁷. We determined a measure of “phenological mitigation” by subtracting July temperatures from temperature during peak flight season. This gave us an idea of whether or not butterflies are flying earlier to avoid hotter temperatures. The positive association between July temperature and “phenological mitigation” suggests that butterflies are buffering overall hot climates by flying earlier during cooler months. We also asked if cooler, earlier flight times are available to the butterflies to buffer future warming. In twelve of fifteen sites, caterpillars started growing as early in the year as it was possible for them to feed. At these sites, any advance in timing would happen at the expense of adult size and the amount of offspring produced. At the three remaining sites, this sort of shift was possible without shortening time for growoth.

Despite the known climate sensitivity of Edith’s checkerspot butterfly, we expect that this species’ potential for rapid evolution⁸ and variation in habitat use² will enable it to persist across most of its range as climate warms. However, particular subpopulations may prove extremely vulnerable. A prime example is the federally endangered Bay Checkerspot, Euphydryas editha bayensis. Although it is located near the center of the species’ latitudinal range, the Bay Checkerspot operates close to the limits of its ecological tolerance⁹.

We wish to thank Jacob Johansson, Niclas Jonzén and Jan-Åke Nilsson for inviting us to contribute with our paper to the special issue about “Phenological change and ecological interactions.”

References

1.  Merrill, R. M. et al. J. Anim. Behav. 77, 145 (2008).

2.  Singer, M. C., McBride, C. S. Evolution. 64, 921 (2010).

3.  Mikheyev, A. S., et al. Mol. Ecol. 22,4753 (2013).

4.  Parmesan, C., Singer, M.C., Harris I. Anim. Behav. 50,161 (1995).

5.  Parmesan, C. J. Insect Behav. 4, 417 (1991).

6. Parmesan, C. Nature. 382, 765 (1996).

7.  PRISM Climate Group. Oregon State University (2004).; http://prism.oregonstate.edu

8.  Singer, M.C., Parmesan, C. Nature. 361, 251 (1993).

9  Singer, M. C., Parmesan, C. Phil. T. Roy. Soc. B. 12, 3161 (2010)

Welcome to Oikos’ Editorial Board, Dr Andrew MacDougall, University of Guelph. Visit his webpage here. And read more about him below:

1. What’s you main research focus at the moment?
How the co-varying influences of global environmental change transform fundamental processes relating to diversity and function in terrestrial systems

2. Can you describe your research career? Where, what, when?
I have been at the University of Guelph since 2006; prior to my PhD, I worked for several years as a government research biologist in eastern Canada.

3. How come that you became a scientist in ecology?
a love of the outdoors, and a curiosity about the workings of the natural world

4. What do you do when you’re not working?
[laughter] being dad, road biking, yoga

The last issue from 2014 is online.

We selected the meta-analysis by Kulmatisk et al on the impact of soil foodwebs on plant growth  and the forum on the relative importance of neutral stochasticity in community ecology by Vellend et al. as editor’s choice. These two papers create synthesis in community ecology. The first by pointing the first widespread support for the presence of trophic cascades in soils, the second one by providing conceptual clarity on the main prevailing stochastic processes in community dynamics.

 

Kulmatisk and colleagues conducted a meta-analysis based on 1526 experiments that measured plant growth responses to additions or removals of soil organisms to test how different soil trophic levels affect plant growth. They demonstrate the top down control by predators and parasites on belowground herbivory and estimate the impact of belowground biota on plant growth overall positive and strong. Omnivory in the soil food web generally increases plant productivity by (i) pest reduction and (ii) increasing nutrient cycling.

 

Vellend and colleagues continue to set the scene of community ecology. They address several profound philosophical, theoretical and empirical challenges on the relative importance of stochasticity in community dynamics. They clearly clarify differences between ‘stochastic’ or ‘neutral’ processes by synthesizing their importance in different community processes. They subsequently provide a guide how different observational and experimental approaches will forward the field by allowing a thorough understanding of the role of neutral stochasticity in community ecology.

 

Enjoy!

Dries Bonte, Editor in Chief

Very welcome, Dr Sara Magalhaes, to the Oikos Editorial Board! Get to know Sara by visiting her webpage and read the mini-interview here:

1.     What’s you main research focus at the moment?

I work mainly with spider mites, which are herbivorous haplodiploid tiny spider-like creatures. Being easy to rear and with a short generation time, spider mites are easily amenable to experimental evolution, a methodology I find very powerful. With these mites, I ask questions within the general fields of host-parasite interactions (in which mites are either the host or the parasite), sex allocation, and mating strategies. I also do collaborative work on fruit flies, again on these topics.

2.     Can you describe you research career?

I did my undergraduate education at the University of Lisbon, with an Erasmus in Toulouse, then moved to the University of Amsterdam. There, I ended up doing my PhD thesis, under the supervision of Maurice Sabelis and Arne Janssen, and a lot of help from my colleagues Marta Montserrat, Belen Belliure and Maria Nomikou. The thesis concerned mainly the ecological consequences of antipredator behaviour. By the time I ended the thesis, in 2004, I felt the need to address the evolution of traits as well, so I moved to Montpellier to do a post-doc with Isabelle Olivieri. I took the mites with me and did experimental evolution of mite adaptation to novel host plants. I then decided to go back to Portugal, where I did a brief post-doc at the Gulbenkian Science Institute, again with experimental evolution but with bacteria and nematodes. Finally, in 2008, I came back to the University of Lisbon, where I established my own group with spider mites and several really cool students.

Photo: Jacques Denoyelle

3.     How come that you became a scientist in ecology?

I always thought that integrative sciences were more interesting. People that spend their whole lives studying a single molecule still give me the creeps, although I realize that this is also necessary…

4. What do you do when you’re not working?

I used to do lots of different stuff, I was in theatre groups, and danced tango a lot, went to lots of concerts and to the movies, but now that I have small kids my activities have switched to going to playgrounds and kid parties. In the summer, which in Portugal lasts around 6 months, it’s nicer because we go to beach, which everybody loves.

 

Human activities drastically reduce biodiversity at various taxonomic levels. While much of the current effort in research and biological conservation focuses on species diversity, the importance of intraspecific genetic diversity is sometimes overlooked. At the same time, genetic diversity within and among populations is the fundamental unit of biodiversity because it provides raw material for the adaptation, evolution and survival of species and individuals.

Plantation forests are usually composed of selected stock bred for desirable silvicultural properties (e.g., rapid growth rate and high timber quality) and as a result often have a narrower genetic basis than the wild populations of the same species. Even when natural regeneration is used, a limited number of seed trees may result in less diversity in the regenerated stand compared to the original one. Commercial applications of vegetative propagation of forest trees (clonal forestry) may lead to the further reduction in genetic diversity up to only a few or even a single genotype per plantation. For instance, micropropagation is commonly used to clonally multiply superior birch genotypes in Finland, both for commercial production and for breeding purposes, but it has been proven successful for only a limited number of birch genotypes. Limited number of commercially available birch clones may thus narrow the genetic diversity of planted birch stands.

Figure 1. Micropropagated birch planted inside plastic vole protector in 2000.

Limited genetic variation in plant stands can make them more vulnerable to pest invasion and outbreaks; if all the plants in a stand are genetically identical and susceptible to the same pest species, pest populations will spread rapidly from one plant to another. In agriculture, mixed planting of susceptible and resistant genotypes has been successfully used as a control tactic for plant pathogens in annual crops. However, the potential of using genotypes mixtures in plantation forestry for reducing pest damage has been little explored so far, although there are indications that mixtures may sometimes be of great value for controlling pests and diseases of trees as well, at least in short rotation energy forestry.

In this study, “Additive and non-additive effects of birch genotypic diversity on arthropod herbivory in a long-term field experiment”, now published Early View in Oikos,  we have experimentally tested whether genetic diversity of silver birch affects leaf damage by various arthropod pests. Silver birch (Betula pendula Roth) has broad distribution in the Northern Hemisphere and is one of the most important deciduous tree species in Finland, both ecologically and economically. In 2000, we established an experiment in Satakunta, SW Finland, by planting 8 different clones of silver birch which were obtained by micropropagation of vegetative buds of mature trees of southern Finnish origin. The eight clones selected for the experiment are known to differ in their growth and leaf characteristics as well as in resistance to herbivores and pathogens. The clones were planted in monoclonal plots and in different combinations of 2, 4 and 8 clones per plot. Damage by different types of arthropods was monitored on these experiments several times over nine years.

Figure 2. View of experimental area in 2014

 

Results show that genotypic variation and diversity strongly influenced birch herbivory, but that patterns varied among arthropod guilds and over time (within and across years). In particular, leaf-chewing damage and leaf galls were significantly less abundant in genotypically diverse stands than in stands with only a single genotype. However, leaf-rolling damage was actually higher in diverse stands, illustrating how arthropod guilds may differ in their responses to genotypic diversity.

 

A: leaf chewing by sawfly larvae.

B: leaf mining by Eriocrania sparmanella

C: leaf skeletonizing

D: leaf rolling

E: galls caused by eriophyid mites.

More detailed analyses at the genotype level revealed further interesting patterns. Genotypes varied considerably in their susceptibilities to most herbivore guilds examined, demonstrating that genetic variation existed among the 8 genotypes selected. Interestingly, the susceptibilities were not constant over time or among the guilds. This indicates that resistance to these guilds of herbivores is largely uncoupled genetically and that there is not a single genotype that is resistant to all types of herbivory. Furthermore, we observed shifts in the resistance rankings of genotypes between seasons and across years. Thus, while one genotype may be the most resistant to early-season leaf herbivory one year, it may not be the most resistant to leaf herbivory in the late season or the following year.

To try to understand the mechanisms underpinning the diversity effects observed, we used null modelling to test whether herbivory in diverse plots differed from expected levels generated from data in monoclonal plots. We found that diversity effects depended significantly on genotype, revealing that non-additive mechanisms operate in this system. In particular, more resistant genotypes often experienced greater than expected levels of herbivory (associational susceptibility) while more susceptible genotypes often had less than expected herbivory (associational resistance). These patterns indicate that associational resistance and susceptibility can occur simultaneously in genotypically diverse plots, presumably due to the reorganization of arthropods among genotypes. While these diversity effects do not scale up to influence plot-level rates of herbivory, they may strongly influence the fitness of plant genotypes within diverse plant stands, potentially playing a strong role in the evolutionary ecology of forest trees.

This study illustrates the value of long-term experiments for testing how genetic diversity influences the arthropod communities of woody plants. Diversity effects were complex and varied among the arthropod guilds, among the genotypes, and across time. Only by sampling multiple times over many years and including data for different kinds of herbivores did we detect these patterns. Future work looking at how plant phenotypes relate to these patterns and observing the behaviour of various arthropods can provide further insight into the mechanisms driving genotypic diversity effects.

Decades of ecological research have focused on interactions between herbivores and the chemical defenses of plants. However, far less is known about how effective physical defenses (spines, thorns, etc.) are against mammalian herbivores. It has been argued that co-evolution between plant physical defenses and herbivores might underly the confusing results across many studies.

Therefore, we conducted a study, now published Early View in Oikos “Evolutionary irony: evidence that ‘defensive’ plant spines act as a proximate cue to attract a mammalian herbivore”,  focused on the interaction between the white-throated woodrat (Neotoma albigula) and the cactus on which it specializes. There is great variation in how heavily-defended the cactus plants are, ranging from almost spineless to very spiny in the area where we study these animals (Castle Valley, UT, USA),

A white-throated woodrat (Neotoma albigula)

 

 

 

A nonspiny cactus plant

A heavily-defended, spiny cactus plant.

 

Woodrats collect large amounts of plant material in their nests that they feed on later. Interestingly, we noticed that the woodrat nests were covered mostly in heavily defended, spiny cacti. This phenomenon caused us to ask whether woodrats preferred spiny cacti, and why that might be.

A cactus plant collected from a woodrat nest. The bottom has been eaten by the woodrat.

 

We performed a number of feeding trials and choice experiments to show that indeed, woodrats do prefer spiny cacti to experimentally despined cacti. This result suggested that woodrats use the cactus spines as a cue for feeding. Nutritional analysis revealed that spiny cacti are lower in indigestible fiber and higher in protein than spiny cacti. We hypothesize that the woodrats may be using the signals of spines to collect a more nutrient-rich plant that they then feed on later.

Our results demonstrate that physical defenses can be overcome by specialist mammalian herbivores. Further, they show that mammalian herbivores can use obvious, visual clues to select plants that they want to consume.

The authors, through Kevin Kohl

 

Walk through a grassland at the peak of summer and you will quickly become aware of how many grasshoppers inhabit the area. But what effect do these grasshoppers and other insect herbivores have on the plant community you are walking through? How does the effect of invertebrate herbivores compare to that of less visible, but also ever present small mammal herbivores? And do these effects depend on the availability of resources? In our study, “Invertebrate, not small vertebrate, herbivory interacts with nutrient availability to impact tallgrass prairie community composition and forb biomass”, now on Early View in Oikos, we aimed to address these questions through an experimental study within a tallgrass prairie ecosystem in eastern Kansas. We factorially manipulated the presence of both invertebrate and small vertebrate herbivores and the availability of soil nutrients and observed changes in plant community composition and productivity over five years.

We found that removing invertebrate herbivores had a profound effect on plant community composition after a few years of treatment. Forb species increased in abundance in the absence of invertebrate herbivores, while grass species decreased. This effect was particularly strong under conditions of elevated nutrient availability. Surprisingly, small vertebrate herbivore removals had no detectable effect on grassland plant community composition or aboveground biomass.

A caterpillar chows down on a whorled milkweed (Asclepias verticillata), a plant species that greatly increases in abundance when invertebrate herbivores are removed from tallgrass prairie

 

Perhaps most interestingly, dispersion in community composition among plots where both invertebrate herbivores were removed and nutrient availability was elevated increased compared to the control plots. That is, different forb species came to dominate the replicate treatment plots, likely dependent on initial community composition. Overall, our research points to the important, and often overlooked, role that invertebrate herbivores play in structuring grassland communities. Future research aimed at continued investigation of the effects of invertebrate herbivory on plant communities would be worthwhile.

 

We welcome Professor Leif Egil Loe, Aas, Norway to the Oikos Editorial Board. Who is Leif Egil then? I asked some questions to get to know him better:

1. What’s you main research focus at the moment?

Most of what I am working on is related to ungulate ecology. I am involved in two long-term projects. The first is a population study of Svalbard reindeer initiated by Steve Albon and Rolf Langvatn in 1994 and still running on the 20th year. Current focusof that project is to understand mechanisms of population dynamics and aspects of life history evolution. I am also very interested in spatial ecology, so a subset of our reindeer is GPS-marked. One prediction from climate change is that ground icing events will happen increasingly often in Svalbard, and it has indeed happened two of the five years we have GPS-tracked animals. I am interested in the fitness consequences of different behavioural responses to such events. The second main project is a red deer study with Prof Atle Mysterud as PI. In the past few years we have focussed on the mechanisms of migration, again using GPS-data from several hundred marked red deer. Currently we have a stronger management focus, modelling functional management units and investigating how spatial harvesting patterns are predicted to be affected by climate change.

2. Can you describe your research career? Where, what, when?

I have a masters degree from the University of Oslo (UiO) and the University Centre in Svalbard (UNIS) from 1999 and a PhD from UiO in 2004. The title of the masters was “Habitat selection and site fidelity in Svalbard reindeer” (supervised by Nils Chr. Stenseth and Rolf Langvatn) and the PhD was entitled “Patterns and processes in the life history of red deer” (supervised by Atle Mysterud, Stenseth and Langvatn). From 2004 to 2010 I had researcher positions in Atle Mysteruds lab continuing to work on the red deer project. So as you see I have very much pursued the first two projects I encountered. Between 2008 and 2013 I worked with PhD student Anagaw Atickem on a Mountain nyala conservation project in Ethiopia that at least expanded my study topics geographically. In 2010 I was employed as an Associate Professor in wildlife ecology and management at the Norwegian University of Life Sciences. In 2013 I got promoted to full professor.

3. How come that you became a scientist in ecology?

I think I followed a fairly common path. For as long as I remember I always liked birds, especially feeding them during winter, drawing them and learning their names. In my teens I started collecting butterflies that was a main hobby for 3-4 years. The starting point was identifying species of birds and insects. Starting at university, I got interested in ecology. A study year in Svalbard, and especially meeting Rolf Langvatn, became influential in my career and primed me in on ungulate ecology. Taking a PhD in Stenseths Centre of Ecological and Evolutionary Synthesis, with Atle Mysterud as the main supervisor was fantastic – the best career start one can wish for.

4. What do you do when you’re not working?

I have two kids so a lot of time is devoted to family life. I am a keen small game hunter, like to hike and do cross country skiing in the forest and mountains. My favourite sports activity is “floor ball” that I play once a week.

Global biodiversity is constantly declining, and up-to-date research has shown that biodiversity loss affects the functioning of ecosystems and the services they provide to humans. Biodiversity-ecosystem functioning relations have yet mainly been analyzed in communities where species were randomly removed. In nature however, species are not lost at random, but according to their sensitivity to environmental stress.

In our study “Stressor-induced biodiversity gradients: revisiting biodiversity–ecosystem functioning relationships”, now published Early View in Oikos, we investigated whether biodiversity loss and biodiversity-ecosystem functioning relations in randomly composed diatom communities can be compared to those found in communities exposed to atrazine, one of the most-used pesticides worldwide.

Atrazine exposure resulted in smaller biodiversity loss, but steeper decrease in ecosystem functioning than in randomly assembled diatom communities. This was related to selective atrazine effects on the best performing species, which contributed most to ecosystem functioning but was also most sensitive to atrazine.

Our results imply that biodiversity loss and diversity-functioning relationships found along gradients of environmental stress do not compare to those inferred from the common approach of random community assembly. Species-specific sensitivity and performance need to be considered for a more accurate prediction of biodiversity and ecosystem functioning under stress.

The authors through Christophe Mensens

At first sight, these nematodes all look the same. Nevertheless, they each belong to a different species. Such cryptic species- species that morphologically look the same but show genetic divergence- are more different than we first might think. Previous research already showed that they have different environmental preferences and competitive abilities. In our paper, “Active dispersal is differentially affected by inter- and intraspecific competition in closely related nematode species”, we show that differences in active dispersal behavior occur: in addition to differences in time until first dispersal, the triggers for dispersal also differ between the species. One of the species is most triggered by interspecific competition, two others by competition with conspecifics, and the fourth one is a time-dependent disperser, with fast dispersal regardless of inter- or intraspecific interactions.

These differences in dispersal behavior may be important to explain the coexistence of these species. According to Darwin’s classical competition theory, we can expect that very similar species will not co-occur because competition will be too high. Differences in dispersal behavior may lead to postponed or avoided competition, rendering temporal coexistence possible in a patchy habitat.

The authors through Nele de Meester

Find out what role predation plays in the transfer of less complex parasites in the Early View paper “The underrated importance of predation in transmission ecology of direct lifecycle parasites” by Giovanni Strona. Below is his short summary of the study:

Predation is the primary route for transmission in parasites having complex life cycles. However, despite being one of the strongest evolutionary forces, little is known about its role in the ecology and evolution of simple life cycle parasites (that is parasites that spend all of their life on a single host).

Monogeneans are one of the most abundant group of fish parasites, and are peculiar in that they do not use more than one host during their whole life. Being well investigated, they constitute a good benchmark to explore if predation has some relevance for parasites when not directly involved in transmission from one host to another. For this, I used a large dataset and different approaches to test whether predators and preys share more monogenean parasites than one would expect from their geographical distribution, habitat preference and phylogenetic relationships. It turned out that preys and predators do share more monogenean parasites than expected.

The observed overlap degree was much higher at the genus level than at the species one. This suggests that predation may play an important role in promoting monogenean host range expansion. In addition, a good proportion of considered prey-predator pairs showed a significantly high parasite overlap at the species level. This last result promotes some intriguing hypotheses. In particular it may indicate a tendency of some monogenean parasites to evolve transmission strategies more targeted towards host interactions than towards species specific traits.

Monogenean parasites identify suitable hosts on the basis of various cues related to host physiology and behavior, such as shadows, chemicals, mechanical disturbance, and osmotic changes. Usually, these cues are generated by the activity of single species, but could also result from species interactions. For example, a predator hunting a school of fish may produce peculiar water turbulence, shadows, and specific chemicals, which are stimuli that have already been demonstrated capable of inducing mass hatching in monogeneans. Some monogenean parasites could have developed the ability to identify these cues, and to infect with similar probability a predator and its prey/s. If this hypothesis was true, it would have strong implications on evolutionary ecology, suggesting the existence of a peculiar situation, where some parasites have evolved high specialized host finding behaviors to become more generalist. Morevover, it would indicate that some monogenean parasites could be more vulnerable to coextinctions than suggested by the size of their host range, as their survival would depend on that of both the prey and the predator species.

Variation in size between sexes is something that we associate mainly with animals. But what about plants? Do female plants have larger leaves than males? Find out in the Early View paper in Oikos “Sexual size dimorphism in island plants: the niche variation hypothesis and insular size changes” by Patrick H. Kavanagh and Kevin C. Burns. below is their summary of the study:

Sexual size dimorphism (SSD) is common throughout the animal kingdom. Size differences between the sexes are often extreme and in many cases one sex may be twice the size of the other. While most plants are hermaphroditic, approximately 7% of flowering plants are dioecious (separate male and female individuals). SSD is also common in dioecious plants, yet has received far less attention than SSD in animals. The niche variation hypothesis predicts the degree of SSD to increase for insular populations as a response to increased intraspecific competition.   Many animal taxa conform to this prediction, however SSD of island plant populations had not been investigated.

We investigated differences in SSD between related island and mainland plants by using herbarium material. Specifically, we quantified the sizes of leaves and stems for plants from the New Zealand mainland and surrounding offshore islands. Our results suggest that the degree of SSD is not predictable for island plants, contrary to predictions of the niche variation hypothesis. Furthermore, SSD was consistently female biased on the mainland, however the direction of SSD was not predictable on islands. Our results suggest that both sexes are under selection for increased size on islands. This may contribute to SSD being unpredictable due to the sexes responding to selection at different rates. However, further work is needed to gain a better understanding of SSD in island plant populations.

In our new paper “Marine biodiversity and ecosystem functioning: what’s known and what’s next?” just published online early in Oikos, we synthesise our current understanding of the functional consequences of changes in species richness in the marine realm. For those familiar with the field of biodiversity and ecosystem functioning, the first question might well be: do we really need yet another meta-analysis on this topic? I mean, really. There have been several meta-analyses published in recent years. Do we really need this work?

Well, our answer to the question is yes. Here’s why.

This paper started while we were synthesising data for general biodiversity-ecosystem functioning relationships at NCEAS  in Santa Barbara, USA. We realised that much data from the marine side was missing, as many of those studies did not fit the inclusion criteria set up for our original database. Previous meta-analyses^{1, 2} focused solely on how richness influences resource capture and/or the production of biomass. Marine studies, however, all over the map in terms of what functions they measured: resource use, biomass production, nutrient fluxes, trophic cascades, and so on.

Panel with a sessile invertebrate community. Photo credit: Jarrett Byrnes.

 

So what’s the full picture of how biodiversity-ecosystem influences functions in the ocean – from primary production to biogeochemical cycles?

We got our hands on 110 marine experiments that manipulated the number of species and analysed some ecosystem response. In general, our analyses generally confirm previous findings that the average mix of species uses resources more efficiently and produces more biomass than the average monoculture. We honestly weren’t sure how this was going to fall out, and find great comfort in the generality of the result.

Soft sediment microcosms, Sweden. Photo credit: Karl Norling.

 

 

In contrast, we find a different shape to relationship between biodiversity and ecosystem functions than has been seen previously. The relationship between species richness and production is best described as linear. The relationship between species richness and consumption appear to follow a power function. We find this by using new and more powerful techniques to describing the shape of relationships across multiple studies that we hope future researchers will use as well. (And, yes, we give you all of our code so that you can follow along at home!)

A seagrass field experiment in Finland. Photo shows a polyculture with three species. Photo credit: Camilla Gustafsson.

 

We also identify several gaps in our understanding of marine biodiversity and ecosystem functioning that are ripe for future investigation. First, the number of studies focusing on biogeochemical fluxes is still tiny. We need more. Second, we need more studies in pelagic and salt-marsh environments. Third, we still have only a handful of studies focused on predators. Fourth, the effects of increases in species richness (e.g. due to invasives or range shifts) are poorly understood. And last, we really only looked at relatively simple experiments, using on average only 3 species! We sorely need experiments targeting how spatial scale and heterogeneity, realistic local extinction scenarios from natural (read: large!) species pools, and functional and phylogenetic composition alter the relationship between biodiversity and ecosystem function.

To sum: there’s much work to be done, and we look forward with high hopes to the next generation of experiments exploring the consequences of changes in marine biodiversity.

Three species of crab, used in the experiment in Griffin et al. 20083. Photo credit: Pippa Moore.

 

Now, if you had to explain this study to your mom or dad: the world has an incredible number and variety of different species, but we are losing them due to things like fishing, habitat destruction, and other threats from humanity. We need to understand what the consequences of these extinctions are for healthy and productive ecosystems, which is why researchers conduct experiments where they remove species and see what happens. We summarized data from 110 such experiments and found that losing species, on average, decreases productivity and growth, as well as a myriad of other processes related to how marine organisms capture and utilize resources, like nutrients. These processes ultimately put food on the dinner table and give us clean water. What is most interesting is we expected these declines to be non-linear based on previous studies: you can lose some species up to a point, then it starts to go downhill. The results from our analysis suggest that, for some processes, every species matters! Thus it is imperative that we protect and conserve biodiversity in our world’s oceans.

Lars Gamfeldt and co-workers

References:

1. Cardinale, B. J. et al. 2006. Effects of biodiversity on the functioning of trophic groups and ecosystems. – Nature 443: 989-992.
2. Cardinale, B. J. et al. 2011. The functional role of producer diversity in ecosystems. – American Journal of Botany 98: 572-592.
3. Griffin, J., de la Haye, K., Hawkins, S., Thompson, R. and Jenkins, S. 2008. Predator diversity effects and ecosystem functioning: density modifies the effect of resource partitioning. – Ecology 89: 298-305.

 

Conservation biologists and climate change researchers are worried by the observed phenological changes, that is, timing of biological events. These concerns are partly motivated by the expected species-specific and thus potentially non-parallell phenological shifts among interacting species, leading to what is often-named ’mismatches’ for ’plants (that) are finely tuned to the seasonality of their environment’.
These concerns are rarely accompanied by empirical data showing that phenological change leads to changes in fitness or population dynamics, and most often they focus on a single phase in the plant’s annual cycle. In our study, we observed the timing of flowering, fruiting, dispersal and germination and their effects on fitness components in the insect-pollinated, and bird-dispersed shrub Frangula alnus (Rhamnaceae).

Frangula alnus bicolored fruit display

In our study “Are mismatches the norm? Timing of flowering, fruiting, dispersal and germination and their fitness effects in Frangula alnus (Rhamnaceae)” we found that the effects of earliness (in phenological terms) varies between different phases and between different fitness components. Thus, we argue that the timing and temporal distribution of every single phase, e.g., flowering, fruiting or germination, is not at all finely tuned, but a robust compromise to selection pressures varying between phases and years.

Kjell Bolmgren and Ove Eriksson

The higher up, the smaller the insects…or? Dispersing insects might be different. Read more in the Early View paper “Dispersal potential impacts size clines of grasshoppers across an elevation gradient” by Richard Levy and colleagues. Below is the author’s own summary of the study:

Insects found across elevation gradients that experience seasonality are commonly observed to become smaller with increased elevation. This results primarily from a reduction in season length at higher elevations, which selects for individuals that mature as early as possible, despite losing the benefits of a larger body. However, our study finds that this pattern can be completely negated in species of grasshoppers that exhibit morphologies and behaviors that increase their dispersal. To see if the nullification of this evolved pattern influenced the reproductive fitness of large bodied, high elevation grasshopper populations, we brought females back from the field and allowed them to lay clutches of eggs in the laboratory. The grasshoppers were then dissected and the functionality of their ovarioles (female insect reproductive organs) was analyzed. While we did find that ovariole functionality decreased due to higher dispersal, we were unable to measure any effect on the size and number of eggs laid. Overall, our study provides evidence that dispersal among populations can reduce or counter traits evolved to best suit local conditions.

Ovarioles from Melanoplus pellucida

 

Melanoplus dodgei from alpine site

Ecologists strive to understand the causes of the observed variability in population abundance and distribution. 1/f noise models and multifractals provide complementary conceptual and analytical frameworks to characterise variability in temporal and spatial series of environmental and ecological data. In our paper, “Multifractal spatial distribution of epilithic microphytobenthos on a Mediterranean rocky shore”, we combined these techniques to investigate the spatial distribution of epilithic microphytobenthos (EMPB) forming biofilms on rocky intertidal surfaces.

Marine biofilms, which mainly consist of photosynthetic organisms (diatoms, cyanobacteria and spores of macroalgae) embedded in a polysaccharide matrix, are important but almost neglected components of rocky intertidal habitats. Indeed, they substantially contribute to coastal primary productivity, provide food for grazing gastropods and facilitate the settlement of algal propagules and larvae of sessile invertebrates. Previous studies investigating the spatial distribution of soft bottom biofilms and periphyton communities highlighted that these microscopic organisms form complex multifractal spatial structures. On the bases of these results we hypothesized that power laws and multifractals could best describe the spatial distribution of rocky intertidal biofilms. We tested this hypothesis applying spectral analysis and multifractal geometry to nearly-continuous EMPB biomass data, obtained from calibrated colour-infrared images.

Our results support the hypothesis that 1/f noise spatial patterns are also multifractal. We interpreted these findings from two different but not mutually exclusive perspectives: either as the result of the superimposition of several biotic and abiotic processes acting at multiple spatial scales or as the hallmark of self-organization. Both interpretations stress the importance of local biotic interactions, either positive or negative, in shaping spatial pattern of distribution of EMPB biomass, while differing in the way environmental processes are supposed to affect microalgal abundance. The first interpretation is that environmental processes associated with temperature, insolation and moisture exert a direct effect on EMPB. Conversely, under self-organization, the influence of these abiotic variables is indirect, being mediated by the presence of the polysaccharide matrix in which microalgal cells are embedded.

Martina Del Bello

As announced in the August issue, Oikos is publishing meta-analyses at an increasing rate, and similar to the transformative capacity of the Forum section, a dedicated section associated with formalized, replicable systematic reviews and meta-analyses will also advance discovery and integration via effective curation. Chris Lortie will act as EiC for this section, and we strive to make all decisions and reviews with one month (provided referees respond in a timely manner), and referees will be selected to review not only the topic explored but also the elements of synthesis included. These efforts will be open-access published as editor’s choice to stimulate positive practices in our field more broadly and to facilitate longitudinal cross-study contrasts of ecological syntheses. Ecology is a very diverse discipline, and big-science ecology needs big bridges between our synthetic discoveries. Granda and colleagues’ meta-analysis on the physiological responses of woody plants to extreme climatic conditions was therefore selected as EiC for November. Understanding responses of species to winter cold and summer drought extremes is especially relevant in face of ongoing climate change. The authors compiled the existing literature on these responses of woody plants from temperate zone and show that that deciduous angiosperms were most sensitive to climatic stress and that evergreen species show less pronounced seasonal responses in both leaves and stems than deciduous species.

The October issue has been dedicated to a set of integrative research papers that bring synthesis on the functioning of soil food webs brought together by one of our editors Ulrich Brose. You can read more on this here. We jointly published with this special issue the forum paper of Fabrizio and colleagues as editor’s choice. They provide a concise synthesis on the role of top predators in food webs. Ecological research on the role of top predators in food webs is becoming increasingly important and popular in terrestrial (see for instance Boersma et al) and marine systems (e.g. Goyert et al; Rizzari et al. ) but also from a more theoretical point of view (e.g. Berg et al.). This exponentially expanding literature is, however, strongly associated with a rapid disintegration into specialized, disconnected subfields for study (e.g. vertebrate predators versus invertebrate predators, community ecology versus biological control etc.). The authors argue that this results in a loss of coherent, integrated understating of the role and importance of these species in ecosystems.

You might, sometimes, have heard the phrase ‘everything is connected’. Maybe you are thinking about computers and mobile phones, but in fact this statement is particularly true in nature. For instance, we know that species are not isolated entities, instead they are part of communities in which multiple different species are interacting with each other. Some of these interspecific interactions are cooperative and positive for all interacting partners, and are called mutualistic interactions. Virtually all species on Earth are involved in one or more mutualistic interactions. Specifically, the interactions between plants and their pollinators may be some of the most studied ones, as nearly 85% of plants rely on animals for pollination service. In the last 20 years the study of pollination interactions using network analysis has been a hot topic in ecology. Networks have proven to be a useful tool to unravel patterns in plant-pollinator interactions at the whole community level. Usually, almost all plant-pollinator networks are constructed at the species-level (species-based networks), i.e. nodes in the network are plant and animal species and links represent the interactions occurring between them (e.g. flower visits). However, species are composed of populations of individuals and those individuals are the true actors establishing interactions in nature. Even more interesting is the fact that conspecific individuals are phenotypically and behaviourally diverse with respect to, e.g. size, sex, age, and social status, which also might imply that their foraging decisions become different. Most ecological networks studied to date have not considered this intraspecific variation in interactions, despite the importance of individual variation within natural populations addressed in the theory of evolution by natural selection. For that reason, moving from species-based networks to individual-based networks, to disentangle a process, which can be defined as network downscaling, is probably one of the major challenges right now in ecological network research.

 

Network downscaling. In traditional species-based networks each node represents a species (red nodes are pollinators and green ones are plants), but if we decompose a species into its constituting individuals we can obtain an individual-based network. In the figure, downscaling is only represented for the pollinator subset.

 

In an attempt to fill this gap of knowledge, we got the idea of downscaling an entire pollination network to the individual level for the pollinator subset and explore network patterns at both interacting scales: species and individuals. This was possible with the study of pollen loads of insect individuals. Insect flower visitors in two mountain shrub communities from Mallorca (Balearic Islands) were captured, and later in the laboratory, pollen carried by each one was identified and quantified under the microscope. It was a highly time consuming and difficult task, but it paid well off as it provided a record of the flowering species visited by each individual pollinator over time. Data revealed that generalized species in the plant-pollinator network are composed of specialized and idiosyncratic individuals. The high heterogeneity in individual foraging behaviour and the high individual specialization of pollinators are obviously hidden in traditional species-based networks, and thus determine differences in several topological properties between species-based and individual-based networks. Particularly, the modular structure – a broadly described pattern in pollination networks which consists of densely connected groups or cliques of nodes with sparse connections to other groups– is not consistent across networks at the two scales. We found that modularity increases when downscaling networks to the individual level, and we confirmed this result using different modularity detection algorithms. In contrast to the view of modules as a set of taxonomically related species or species with convergent morphological traits in species-based networks, modules in individual-based networks are groups of functionally different pollinators distantly related but with overlapping pollen niches. Thus, interestingly, conspecific individuals are distributed in different modules. Modules showed to have a strong phenological component, and attributes related to the phenophase of plants and individuals even determined the topological roles of nodes in the network. Only when downscaling to the individual level it was possible to detect a dynamical interaction switching within-species and a module turnover throughout the flowering season, thus modules of individuals assembled and disassembled over time.

Study site. The study was conducted on two locations in Puig Major (1445 m), the highest mountain in Mallorca (Balearic Islands).

Methods. Pollinator observations were conducted in the field. Insects visiting flowers were captured and, later, their pollen loads were analyzed in the lab.

 

In conclusion, findings reported in our study, “Increasing modularity when downscaling networks from species to individuals”  (Tur et al.) highlight that network patterns differed across the individuals and the species scales, because much within-species variation exists. This implies that it is not always possible to deduce structure at one hierarchical level from information about structure at an adjacent level. Combining the study of networks at both scales offers the possibility of uncovering important properties and processes, which might influence network stability, dynamics and the outcomes of interactions.

Distribution of conspecifics into modules. One of the objectives in our study was to investigate whether individual-based networks were modular and if this was true, to analize how conspecific individuals were distributed among modules. There are two possibilities: (a) all conspecific individuals belong to the same module, or alternatively, (b) conspecific individuals belong to different modules. In most species we found ‘b’.

 

Module turnover. When downscaling from species to individuals, a module turnover associated to seasonality was identified, so that at a given moment of the season there is predominance of a particular module of individuals. The complete individual-species network and the different slices of each month are shown in the figure.

By Christina Tur

 

 

Yes, made it through the wallaby attack!, No, no, no- no reason to celebrate Eucalyptus trees. Less marsupial browsing – opens up for more insects. Life is just not easy. Read more in the Early View paper “Direct and indirect effects of marsupial browsing on a foundation tree species” by Christina L. Borzak, Julianne M. O’Reilly-Wapstra and Brad M. Potts. Below is their summary of the study: Herbivores have impacts on plant survival, growth and form and these induced changes can have important flow-on consequences to subsequent organisms. Although a large number of studies in eucalypt systems have previously investigated vertebrate feeding preferences and the direct impacts of herbivory, few studies have focused on how herbivores interact to directly affect each other’s feeding preferences, and even less have addressed the indirect plant-mediated effects of herbivores. We investigated the direct and indirect effects of uncontrolled browsing by marsupial herbivores including the common brushtail possum (Trichosurus vulpecula), Bennetts wallaby (Macropus rufogriseus) and the red-bellied pademelon (Thylogale billardierii), in a Eucalyptus system known to have extended community and ecosystem genetic effects. In a common garden trial containing 525 full-sib Eucalyptus globulus families from an incomplete diallel crossing program located in north-eastern Tasmania, Australia, we assessed the genetic basis to herbivore preferences, the impact of a single and repeated marsupial browsing event on tree fitness and morphological traits and the associated indirect plant-mediated effects on a subsequent herbivore, autumn gum moth (Mnesampela privata).

Autumn gum moth larvae (Mnesampela privita)

Common brushtail possum (Trichosurus vulpecula)

Red-bellied pademelon (Thylogale billardierii)

We found that marsupial browsing was not influenced by plant genetics, but spatial components instead affected the pattern of damage across the trial. Marsupial browsing had significant impacts on tree development, morphology and survival, resulting in reductions in survival, height and basal area, an increase proportion in multiple stems, delays in flowering as well as delays in phase change from juvenile to adult foliage. Fitness impacts were minimal in response to a once-off browsing event, but effects were exacerbated when trees suffered repeated browsing.

Trait assessments under way at the Eucalyptus globulus trial site by authors Christina Borzak (left) and Julianne O’Reilly-Wapstra (right).

Assessments of autumn gum moth damage showed that their presence was linked to marsupial browsing, with browsed plants being less susceptible to the insect herbivore. The majority of the effect was attributed to the indirect effects of browsing on tree height, where AGM were attracted to taller trees that were not browsed. Such indirect effects have the potential to influence biotic community structure on a foundation species host-plant, and the evolutionary interactions that occur between organisms and the host-plant themselves.

Predicting herbivore intensity in disturbed habitats is not as easy as it might seem… Results were a bit surprising in “Land-use legacies and present fire regimes interact to mediate herbivory by altering the neighboring plant community” by Philip G. Hahn and John L. Orrock. Below is the author’s summary of the study:

The southeastern United States was once teaming with biodiversity in the sprawling, open pine savannas that stretched from Virginia to Texas. Post-settlement, these biodiversity hotspots were quickly reduced to less than 3% of their original extent, largely through conversion to agriculture and fire suppression. More recently, many agricultural fields have been abandoned and replanted with pine trees. Although these degraded woodlands harbor low levels of biodiversity, they offer tremendous potential to restore lost species. Particularly, ecologists know very little about interactions among plants and insects in these degraded ecosystems. Hypothetically, insect herbivores, such as grasshoppers, could be suppressing plant diversity in these post-agricultural woodlands by preferentially consuming more palatable remnant wildflowers that attempt to reestablish.

The sun rises over a rare remnant longleaf pine savanna, fueling a motley array of biological interactions.

We tested this idea by transplanting native plants into herbivore exclosures within longleaf pine stands on historic agricultural sites. In order to compare disturbed and undisturbed longleaf pine savannas, we also located several stands of remnant longleaf pine savanna. Because some of these stands experienced woody encroachment due to fire suppression, we crossed fire frequency with historical land use as a component of our experimental design. This created a gradient of degradation with either low or high fire frequency stands within post-agricultural or remnant woodlands.

After measuring herbivore density and herbivory rates on our experimental plants for a field season, we found that sites with low levels of plant cover supported small populations of herbivorous grasshoppers, which resulted in low herbivory rates on our experimental plants. These sites were usually degraded by historic agriculture and were extremely fire suppressed.

Sites representing the range of neighboring plant cover at our experimental sites. Insect exclosures or control cages (with holes) were placed over a set of experimental plants.

 

There were more grasshoppers at sites with extremely high levels of plant cover. Herbivory rates were expected to be higher at these sites because there were so many grasshoppers. As it turns out, herbivory rates were actually low because there were many more neighboring plants for grasshoppers to consume. In other words, high abundance of neighboring plants swamped out the negative effect of herbivory on the focal plants. These sites with low herbivory rates tended to be frequently burned remnant sites, meaning that remnant sites can support high populations of both plants and grasshoppers, while minimizing the negative effects that herbivores have on plants.

We found the greatest herbivory rates at intermediate levels of plant cover, where grasshoppers were also in intermediate abundance. These sites tended to historically be used for agricultural or were fire suppressed remnants. In other words, moderately degraded sites had the highest rates of herbivory.

 

Data being generated

By demonstrating that past and present human activities play a key role in present-day plant-herbivore interactions, our work has several important implications for basic and applied ecology. The findings provide a starting point to predict when and where herbivore density or neighboring plants will be important drivers of herbivory. The results also have implications for the recovery of biodiversity in post-agricultural lands and other systems affected by human disturbance by generating predictions about which habitat types will be more susceptible to herbivores.

Aptly described by the naturalist Arthur-Miles Moss, the life of a caterpillar is a virtual struggle for safety from formidable predators, ruthless parasites, and fatal pathogens. To cope, caterpillars possess an array of anti-predator adaptations, or defenses, which aid them in the struggle. An individual caterpillar might employ camouflage, chemical defenses, hairs, spines, and aggressive behaviors to escape or repel its enemies. Despite the fact that these defenses constitute some of the classic examples of adaption, we still know very little about their effectiveness against predators in a natural community context.

 

The bold, gaudy colors of certain insects have arrested the eye of many a naturalist. Alfred Russel Wallace and Henry Bates, who collected butterflies in the Amazon, proposed an ingenious evolutionary explanation for the flashy appearances of many insects. They argued that conspicuous colors on insects are actually warning signals to would-be predators, such as birds, which advertise underlying chemical defenses. The stronger the signal, the clearer would be the message: “Don’t mess with me, I’m poisonous.” Thorough experimental confirmation of this idea, called aposematism, did not come until the second half of the 20^th century.

Figure 1. Aposematic caterpillar of the monarch butterfly on its milkweed host plant. Photo by Michael S. Singer.

The great Victorian naturalists likewise surmised that camouflage was another important defense of insects against bird predation. Observations of caterpillars, katydids, and walking sticks in their natural environments revealed a wondrous precision in the match between the insect’s appearance and the vegetation upon which it lived. Darwin’s and Wallace’s theory of natural selection was the best scientific explanation: only the best camouflaged individuals of each species would escape detection by predators.

 

Figure 2. Camouflaged inchworm caterpillar on its host plant, manzanita, in southern Arizona. Photo by Michael S. Singer.

 

Over the last 50 years, many additional, important observations and experiments have reinforced these evolutionary theories of prey defense. But the vast majority of experimental studies used captive avian predators or artificial prey (such as dead or artificial insects) exposed to wild birds, leaving some question about the effectiveness of aposematism and camouflage in natural predator-prey interactions, which are notoriously difficult to observe directly in the wild. In the mean time, new techniques and technologies have emerged that allow researchers new modes of studying prey defenses in the wild.

Figure 3. Black-capped chickadee with a captured caterpillar in one of the forest sites used to study bird predation of caterpillars in Connecticut. Photo by Christian Skorik.

 

Enter the new study by Lichter-Marck and colleagues, “The struggle for safety: effectiveness of caterpillar defenses against bird predation.” This study used a bird-exclusion field experiment set in the forests of Connecticut, USA to test evolutionary theories of prey defense in the context of a natural ecological community. Over four years, the research team surrounded hundreds of experimental tree branches with garden-variety bird-proof netting, matching each experimental branch with a control branch lacking netting. The netting was applied at the beginning of each growing season, and allowed caterpillars to come and go while preventing access to insectivorous birds. Three weeks later, the researchers returned to each branch and collected the caterpillars living on them. By experiment’s end, the caterpillar species with the largest proportional increase in numbers in experimental branches (protected from bird predation) relative to control branches (open to bird predation) were inferred to suffer the most bird predation. By measuring the defensive traits of each caterpillar species and correlating them with the inferred magnitude of bird predation, the researchers could determine which traits were most effective as defenses against bird predation.

 

 

Figure 4. Red maple branch covered with a bird-exclusion net, one of the experimental branches used in this study. Photo by Christian Skorik.

 

This unique methodological approach supported the main prediction of aposematism theory: among the 38 species of caterpillars that were numerous enough to analyze, those that possessed warning signals, such as bright coloration, received the most protection from birds. But the study revealed another, critical aspect of the warning strategy of defense: stereotypical resting location. The caterpillar species most protected from birds combined warning signals with highly stereotypical resting locations on the plant. That is, their appearance and their location together provided the warning signal to birds. This finding highlights the relatively neglected behavioral aspect of warning strategy of defense.

 

Figure 5. A warningly-signaled caterpillar species (Nola triquetrana) on its host plant, witch hazel, at one of the forest sites used in this study. Photo by Michael S. Singer.

 

Yet the majority of the 38 caterpillar species did not possess warning signals, instead employing camouflage as their primary defensive strategy. Because visual camouflage can result from several different tricks in appearance (disruptive patterns, countershading, etc.), the magnitude of camouflage can be difficult to measure. The researchers turned to an increasingly used method, the human proxy predator assay. In this assay, human participants were shown digital images of the caterpillar species resting on their host plants, and a computer program was designed to record how quickly each participant located each caterpillar with an accurate click of the mouse. The longer it took, on average, to find a caterpillar species, the greater the magnitude of camouflage was inferred.

 

Figure 6. A camouflaged caterpillar species (Catocala ultronia) on its host plant, black cherry, at one of the forest sites used in this study. Photo by Michael S. Singer.

 

In support of evolutionary theory of prey defense, the study found that the caterpillar species with the greatest inferred magnitudes of camouflage received the most protection from birds. Once again, this part of the study revealed a behavioral twist. A caterpillar species’ frequency of behavioral responsiveness to attack, measured independently, worked against the effectiveness of camouflage. This finding suggests that effective camouflage requires not only an appearance that matches the prey’s background, but also behavioral maintenance of the cryptic posture in the face of physical disturbance.

The authors, through Michael S. Singer

While most people know the aboveground part of forest ecosystems, very few have caught a glimpse of the belowground environment that comprises a highly diverse fauna. The number of species co-occurring on less than a square meter habitat ground (or a cubic meter of habitat volume) exceeds that of the aboveground compartment by far. In consequence, forest soil communities have been called “poor man’s rainforest”. Nevertheless, we still do not know much about the animals living in these “next-door” habitats and the structure of their communities.

Impression of a central European beech forest. Much more is known about the aboveground animals and their interactions than about the belowground communities that carry out the critically important ecosystem functions of litter decomposition and nutrient recycling.

 

Why is our knowledge about forest soil communities so limited? Progress in our understanding of soil communities and processes has been hampered by the chronic lack of data for complex soil food webs of high resolution. This is caused by aggregation of populations in coarse functional groups, whose species often span multiple trophic levels from primary to secondary or tertiary predators. In addition, soil is an opaque medium leading to a limited visibility of interactions. Further, detritivores typically ingest a multitude of intermingled resources hampering identification of what the animals actually digest and live on. In the recent years, new molecular methods have emerged providing the possibility to unravel belowground interactions and the complex structure of forest soil food webs.

 

A soil core provides an impression of the complex structure of the belowground habitat. This environment comprises a highly diverse and complex animal community spanning several trophic levels.

The special issue “Into darkness” comprises several studies of central European beech forest soil communities. The studies included in this special feature fill employ state-of-the-art methods to unravel general feeding guilds by stable isotopes (Klarner et al.) as well as specific directed feeding interactions by molecular gut content and fatty-acid analyses (Ferlian and Scheu, Günther et al., Heidemann et al.). This allowed the construction of the first highly-resolved complex soil food webs (Digel et al.) and analyses how they respond to external drivers such as the nutrient stoichiometry of the basal litter (Ott et al.) and climate change (Lang et al.). Together, they provide a unique impression of a voyage into darkness.

Ulrich Brose, Editor of the Oikos Issue “Into Darkness”

 

 

Grasshoppers tend to increase in abundance during drought, no decree, or increase…Find out which and when in the Earl View Oikos paper “Water stress in grasslands: dynamic responses of plants and insect herbivores” by Paul A. Lenhart and co-workers. Below is their summary of the study:

When I first saw the climate projections from NOAA in 2011 that there would be a severe La Niña-fueled drought I was worried that my fieldwork season would be a bust. In 2011, Texas, as well as much of the south central United States of America, suffered through the worst seasonal drought since modern record keeping began in 1895. The drought had severe economic and ecological impacts across the region, but I was focused on my main study organism: grasshoppers. These insects are a very important component of grassland ecosystems, and for the past two years I, together with my co-supervisors (Micky Eubanks and Spencer Behmer), had worked in the grasslands and savannah of central Texas studying a vibrant grasshopper community, consisting of over 56 species. I was working to understand the diet breadth of some of the key species, including their macronutrient regulation behavior, while also quantifying competitive dynamics between these species.

 

Examples of grasshopper diversity. Clockwise from the top left: Melanoplus packardii, Hadrotettix trifasciatus, Acrolophitus hirtipes, Phaulotettix eurycercus.

 

Prior to 2011, one of our sampling seasons (2009) was slightly drier and we found a decrease in grasshopper density and abundance. This went against many previously published observations of grasshoppers and other insect herbivores having larger populations in drier years. The proposed mechanism in the literature is that plant nutrient content actually increases with water stress. However, studies that measure the effect of water stress on plant nutrients typically use greenhouse-reared plants or crop species, and generally measure plant quality as simply a function of nitrogen content. We now know that plant dietary quality is much more complex, and in particular that herbivores actively regulate their protein and carbohydrate intake. Therefore, we decided to change course from our originally planed competition experiment. Instead, we took advantage of the coming drought to conduct a manipulative study in order to gain insights into what happens to native plants, and herbivore behavior, when the rains do not come

            We started our experiment early enough in the season to quantify, over time, the effect of water stress on the native grassland plant’s quality, quantity, and diversity. We marked off small open plots distributed across the grasslands of the Balcones Canyonlands National Wildlife Refuge. Half of these plants were left alone to suffer through the drought and we watered the other half [laboriously] by hand to mimic average summer rainfall. We did this through the growing season and took plant samples and visual grasshopper surveys monthly; in each plot individual grasshoppers were identified to species by sight. After completing each grasshopper survey, we measured grass and forb species richness, and took samples back to the lab to assess biomass and macronutrient content. Specifically, we quantified both digestible protein and nonstructural carbohydrate content in bulk samples of grass and forb tissues using biochemical assays.

 

Behind the scenes of watering plots by hand in the field.

 

            At the end of the summer we found that drought reduced grasshopper abundance and diversity, relative to our water supplemented plots. Using our knowledge of different grasshopper species diets, we grouped species into functional feeding groups and found that functional groups responded differently to our watering treatments. Forb specialists seemed unaffected by the drought while grass-feeders and mixed-feeders (grass+forbs) were significantly less numerous in the unwatered plots. These different grasshopper responses were due to their particular feeding biology and the fact that grass and forbs responded differently to water stress. We go into more detail in the manuscript, but in short, forbs decreased in diversity and experienced a significant shift in their macronutrient profile over time, becoming less protein biased. In contrast, grass biomass was reduced by water stress, but grass protein-carbohydrate content was similar between our two water treatments.

 

A freshly watered plot in a parched grassland.

 

Our results are significant because we used naturally-growing, drought acclimated plants, and quantified protein-carbohydrate content – which are the two most important nutrients that affect insect herbivore feeding behavior and performance. Our research provides valuable data on how plant macronutrient content, biomass, and diversity co-vary in the field, and such data can be used to parameterize models that can help us better understand how generalist herbivores forage and perform under drought conditions, which are predicted to become more common as climate change intensifies. Although more work is required, we envision the use of remote sensing technology, measuring plant quality, biomass, and diversity, to better manage insect pests in rangeland ecosystems.

 

Mixed-grass oak savannah on the Balcones Canyonlands National Wildlife Refuge during a wet summer.

Ecological networks quantify the diversity of direct and indirect interactions taking place in nature. However, due to their complexity, ecologists rely heavily on the use of metrics to summarize aspects of network structure thought to be of biological importance. Many of these structural features are non-random and strongly conserved across diverse habitats and species assemblages, begging the question: what factors determine network structure? The most successful hypotheses to explain these patterns are the neutrality and biological constraints hypotheses, which posit that species interactions can be explained by trait mismatches, and relative abundances respectively. In the Early View paper “Species traits and relative abundances predict metrics of plant-pollinator network structure, but not pairwise interactions” in Oikos, we Colin Olito and Jeremy W. Fox, evaluate the relative ability of trait-based and neutral models of species interactions to explain the structure of a temporally resolved alpine plant-pollinator visitation network.

 

An unidentified muscid visiting Erigeron peregrinus. Although their charm often goes unappreciated, flies are by far the most diverse and abundant pollinators in the alpine. Interestingly, many of their behaviours that facilitate pollination differ markedly from more intensively studied foraging pollinators, such as bumblebees. Understanding their crucial role in alpine and high-latitude plant-pollinator communities will require a greater understanding of both their reproductive and foraging biology. Photo credit: Martin Fees.

As our title suggests, species traits and relative abundances successfully predicted every metric of network structure tested, but failed to predict observed interactions. That is, a variety of models can predict network metrics well, but for the wrong reasons. We explore the implications of this contrast, and highlight potential problems with the use and interpretation of network metrics. We also found that species phenologies (the timing of flowering or pollinator activity) always out-performed neutral models at predicting pairwise interactions, and discuss limitations of neutral models of network structure, particularly when species interactions are under-sampled. We suggest that future progress in explaining the structure and dynamics of ecological networks will require new approaches that emphasize accurate prediction of species interactions rather than network metrics, and better reflect the biology underlying species interactions.

Sampling plant-pollinator interactions in a low-alpine meadow in Kananaskis Country, Alberta, Canada. Photo credit: Martin Fees.

Bat acoustic signals might seem rather simple. yet, there are individual differences. The background to these variations are studied in the Early View paper “Geographical variation in echolocation vocalizations of the Himalayan leaf-nosed bat: contribution of morphological variation and cultural drift” by Aiquing Lin and co-workers. below is their summary of the study:

Animals’ acoustic signals often vary geographically—but how and why? We studied the geographical variation in echolocation vocalizations of a widespread bat species Hipposideros armiger sampled from 17 localities in South China. We asked whether there was detectable population divergence in the vocalizations and whether the acoustic divergence was related to the variation in morphological (forearm length), climatic (mean annual temperature, mean annual relative humidity, and mean annual precipitable water), geographical (latitude, longitude, elevation, and geographical distance), or genetic (genetic distance and population genetic structure) factors. We found remarkable geographical variation in the peak frequency of echolocation pulses of H. armiger, which clustered into three groups: Eastern and Western China, Hainan, and Southern Yunnan. The acoustic divergence was significantly related to morphological differences and geographical distance, but not significantly related to climatic (after controlling for morphological distance) or genetic variation. We also found a correlation between population differences in morphology and climatic variation (mean annual temperature). Our results suggest the action of both indirect ecological selection and cultural drift promote divergence in echolocation vocalizations of individuals within geographically distributed populations.

Figure 1 Himalayan leaf-nosed bat (Hipposideros armiger)

 

 

Figure 2 Oscillogram (above) and Spectrogram (below) of an echolocation pulse of Hipposideros armiger. fpeak = peak frequency.

Male of the harvestmen Zygopachylus albomarginis (with yellow ink marks) inside his mud nest, while a female approaches from the outside [Credit: Gustavo S. Requena]

Nests are extremely important for males’ fitness when reproduction and parental care are associated with these structures. The possession of a nest and its conditions may determine male attractiveness (due to female reproductive decisions) and offspring survival (due to protection against adverse biotic and abiotic conditions). Nest construction and maintenance, however, may also impose costs to males: nest-related behaviors may demand time and energy or may increase mortality risks. The costs and benefits approach is usually used to understand the evolution and maintenance of behavioral traits, and we explored this framework in a study with the Neotropical harvestmen Zygopachylus albomarginis.

 

During the breeding season, nesting males of Z. albomarginis spend several months building, repairing, cleaning and defending their mud nests. After mating, females abandon the eggs under the protection of males, who actively defend them against predators and fungal infection. Although nest defense, nest maintenance, and offspring protection contribute to different components of males’ fitness, they are performed concomitantly and entail similar behaviors. For instance, when a nesting male chases away a conspecific individual, he defends the possession of his nest at the same time he protects the offspring against a potential egg predator (see video below). Moreover, nest maintenance requires males to remove debris and prevent fungal growth inside the nest, actions that also contribute to protect eggs against infection.

 

VIDEO: [Credit: Gustavo S. Requena]

 

In our Early View Paper “Lack of costs associated with nest-related behaviors in an arachnid with exclusive paternal care”, we quantified the costs of nest-related behaviors in Z. albomarginis under natural conditions. Because males are mainly constrained to forage in a small area close to the nest for up to five months, we expected high energetic costs of being associated with a nest. However, we did not find any evidence of decline in the physical conditions of nesting males over time. Interestingly, males may spend several days eating fungal hyphae growing inside their nests, which we suggest constitutes an important food resource to stationary individuals and compensates for energetically costly activities performed for so long periods.

 

 

At the left, we can see a male inside his nest on a fallen trunk without fungus infestation. At the right, the trunk is covered by fungus fruiting bodies, except inside the nest. Nest-cleaning behavior maintains hygienic conditions inside the nest at the same time it provides food to the male, which feed upon the fungus hyphae. [Credit: Gustavo S. Requena]

 

Due to contest injuries over the possession of a nest or its conspicuousness, we also expected high mortality risks associated with nest-related behaviors. The survival probabilities of stationary nesting males, however, were higher than the probabilities of vagrant individuals not associated with nests surviving. This pattern of differential mortality dependent on Z. albomarginis movement activity may be explained by the potential higher chances of encountering predators while moving, particularly walking among trees and crossing the leaf litter.

 

Given that females lay eggs exclusively inside nests and the costs of nest maintenance and defense are extremely low (if not absent), the million dollars question is “why do not all males have a nest?” Males add salivary secretions to the mud at the moment they build the nests. One possibility, therefore, is that the production of such secretion is costly and only males in good body condition would be able to invest in nest construction. Although the costs of performing this activity was not evaluated in our study, the fact that vagrant males may occupy an empty nest or even aggressively attack a nesting male and take over his nest suggests that some individuals rely on usurpation as an alternative reproductive tactic to acquire nests.

 

 

Male resting inside his nest, which contains several black eggs (indicating advanced embryonic development) [Credit: Gustavo S. Requena]

The authors through Gustavo S Requena

What happens when climate change destroys too many habitats? In the Early View paper “Robustness of mutualistic networks under phenological change and habitat destruction” Tomás A Revilla and co-workers present a model predicting potential outcomes.

Below is a short summary of their model and paper:

There is concern that climate change will disrupt the temporal schedules of interactions between plants and their pollinators or seed dispersers. This can make communities vulnerable to other ecological threats, for example habitat destruction. In our paper “Robustness of mutualistic networks under phenological change and habitat destruction”, we studied the simultaneous effects of phenological shifts and habitat destruction on the diversity and structure of mutualistic metacommunities.

We created a spatially-explicit model, in which the network of mutualistic interactions is locally determined by species occupancies, over a finite number of randomly distributed sites. The strengths of the interactions depend on the amount of phenological overlap between the species, affecting local survival. Our model uses empirical data on plant and pollinator phenologies recorded a century ago by Charles Robertson, and in present times and in the same area by Burkle et al (DOI: 10.1126/science.1232728), giving us the opportunity to simulate projected as well as historical changes in phenology. Habitat destruction was simulated by removing sites from the model.

Interactions depend on local species presences and phenological overlaps (in days). Extinctions are caused by site destruction (X) and interaction weakening, e.g. pollinator 1 becomes disconnected and plant 2 losses many interaction-days.

Our results show that habitat destruction causes the gradual erosion of local diversity. A catastrophic collapse in global diversity finally happens when the number of non-destroyed sites becomes too low, and the distances between them too large for recolonization. Recovering from such collapses could be difficult due to the positive feedbacks characterizing mutualisms, which promote alternative stable states.

Under phenological shifts interactions become weaker on average, increasing local extinction rates. When habitat destruction and phenological shifts occur together, they act synergistically: many sites become barren even though they are not destroyed, but for practical purposes these sites behave as if they were destroyed, making metacommunities even more vulnerable to habitat destruction.

Decrease in local and global diversity in response to habitat destruction, for 0, 10, 20 and 30 days of average advance in species phenologies.

Previous research has shown that connectance and nestedness can make mutualistic communities robust against cascading extinctions. We discovered that in effect, these network properties gradually decline with habitat destruction, leaving a very small core of highly connected sites holding the metacommunity before the final collapse. Small alterations in phenology can raise connectance a little bit, due to a few generalist species being able to make new interactions, but overall, large alterations tend to reduce connectance.

We can conclude that the robustness of mutualistic metacommunities against habitat destruction can be greatly impaired by the weakening of mutualistic benefits caused by the loss of phenological overlap.

Image credits: Michel Loreau

We wish to thank Jacob Johansson, Niclas Jonzén and Jan-Åke Nilsson for inviting us to contribute with our paper to the special issue about “Phenological change and ecological interactions”.

Many animals locate resources and orient in rather complex environments like vegetation, coral reefs or leaf litter. How does the presence of a stimulus affect animal movement in such complex environments? And what is the relative contribution of a stimulus vs. the complexity of the environment on animal movements? Find out in the Early View paper “Relative roles of resource stimulus and vegetation architecture on the paths of flies foraging for fruit” by Oriol Verdeny-Vilalta and co-workers.

Below is the author’s summary of the study:

To answer the questions above, we developed a novel method using random walks on graphs to accurately estimate both the perceptual range and the attraction strength from 3D movement trajectories of individuals. The perceptual range gives us an idea of the maximal distance at which a stimulus source biases the movement. The attraction strength measures how the attraction of the stimulus varies at different distances within the perceptual range. Additionally, the methodology enabled us to calculate the relative roles of the architecture of vegetation and of the strength of attraction of a stimulus on the movement of individuals. We applied the methodology to estimate perceptual range and strength of apple maggot flies (Rhagoletis pomonella) foraging for artificial fruit in apple trees of varying complexity.

 

Figure: Main steps (a-d) followed to study animal orientation in complex vegetation structures.

 

In our study we have shown that, conditional on visiting the stimulus location, the presence of the fruit affects animal movement much more than the plant architecture. Moreover, we found that plant complexity makes a minor contribution to defining the perceptual range, but a large contribution to the attraction strength. Thus, we highlight the importance of estimating not only the perceptual range but also the attraction strength of animals, which has been traditionally neglected. Our findings have implications for studying foraging ecology and landscape connectivity. For example, several dispersal models developed to study landscape connectivity incorporate the perceptual range of individuals, but the distinction between perceptual range and attraction strength is still lacking. We expect that landscape connectivity will be higher in animals showing higher attraction strengths for equal perceptual ranges. Given that animals use their sensory systems to make informed decisions and that they move and interact in heterogeneous environments, our approach might be of relevance to the myriad of animals walking and searching in complex environmental structures.

When habitat is lost so are species. One way of investigating the processes underlying this pattern is to pay attention to the identity (not only the number) of species. What happens to between-site differences in species composition when habitat loss transforms formerly continuous habitat into habitat fragments?

Who consults widely applied theoretical frameworks (e.g. theory of island biogeography) to answer this question will come to the conclusion that between-site differences in species composition – i.e. beta-diversity – should increase following habitat loss due to a strong influence of chance on the extinction process. Species are assumed to be ecologically equivalent (all have the same chance of getting extinct) and ecological drift (stochastic changes is species abundance) to increase in importance when populations are small. Further, chance makes it unlikely that populations surviving in different habitat remnants belong to the same species, and homogenization is hindered by isolation.

Who, on the other hand, consults empirical work will find that for various groups of plants and animals it is common to observe that, of the diverse set of species in continuous habitats, it is frequently the same small set of species that persists after habitat loss. Apparently, only certain resistant species are able to survive in fragments, thereby making the species composition in fragments deterministically more (and not less) similar, indicating – in contrast to theoretical models – low influence of chance on species extinction.

In our study “Ecological filtering or random extinction? Beta-diversity patterns and the importance of niche-based and neutral processes following habitat loss “ we investigated how the importance of different processes changes with habitat loss relying on a large database of small mammals in the Brazilian Atlantic Forest. We used a null model approach to quantify beta-diversity and make inferences about the relative importance of niche-based (deterministic) and neutral (stochastic) processes on community assembly at landscapes with varying degree of habitat loss.

Our results did not support a positive relationship between beta-diversity and habitat loss, as predicted by commonly-used theoretical frameworks. Rather, when considering exclusively species composition (disregarding their abundance), beta-diversity was independent from habitat loss, with small mammal communities being more similar than expected by chance in deforested as well as continuously-forested landscapes. However, when species abundance was taken into consideration, we observed a drastic decrease in beta-diversity with habitat loss (i.e. biotic homogenization), thereby indicating an increase (rather than a decrease) in the importance of deterministic processes at landscapes with high degrees of habitat loss. Finally, we observed a drastic change in species composition in a highly deforested landscape, with communities being not just a rarefied sample but rather disproportionately dissimilar to the communities in continuously-forested landscapes.

These results indicate that habitat loss can be seen as a strong ecological filter and species extinction is clearly more influenced by deterministic than by stochastic processes. Against this background, the incorporation of relevant species traits into theoretical models seems to be a useful step forward for the practical relevance of these models. Moreover, pro-active measures seem to be essential to prevent tropical landscapes to go beyond critical levels of habitat loss.

The authors through Thomas Püttker

Understanding lifetime tracks and fitness of long distance avian migrants. This is the title of our DFG-funded German-Israeli Project Cooperation and it is also our quest for several years. Within this project, we aim to explore how movement, survival and reproduction reflect an optimal response to the environment. Evidence is drawn from both theoretical and empirical analyses. Migrants like white storks are particularly interesting for studying these questions as they move large distances and may experience different environmental conditions in different parts of the world with more or less strong impacts on their fitness (carry-over effects). Small-scale movement and behavior and their impact on local population dynamics are equally interesting. Latest technologies allow us unprecedented insights into the life of animals. For example, ultra-light GPS tags allow tracking individuals with very high temporal resolution and over several years, and acceleration measurements allow classifying behavior from distinct acceleration signals. These data together with careful monitoring provide the means for better understanding movement phenomena and their consequences for population dynamics and fitness. 

My main focus within the project are developing behavior-based models for different life-cycle stages (e.g. breeding, migrating, wintering) as well as annual-cycle models that allow studying carry-over effects on individual fitness and population dynamics. Thereby, optimality is an important topic. From evolutionary perspective, fitness-maximizing, optimal behavioral strategies should evolve, determining for example when an individual should start reproducing or start migrating within the annual cycle. On finer temporal and spatial resolution, optimal foraging strategies should evolve which are the focus of our study ‚Individual-based modeling of resource competition to predict density-dependent population dynamics: a case study with white storks‘ (Zurell et al.). Here, we aimed to better understand how density-dependent demographic rates may evolve from home range behavior. To this end, we built an individual-based model for foraging white storks that incorporates both physiology and behavior. We expected that the form of density dependence may differ between different home range behaviors. To our surprise, we also found that it may differ strongly between landscapes with the same degree of fragmentation and the same overall resource availability. This phenomenon is strongly affected by the behavioral trade-offs and by imperfect detection of resources. Thereby, simulated patterns corresponded surprisingly well to empirical patterns although the model was not calibrated. For predicting population or even community dynamics under changing environmental conditions, it seems crucial to better understand these interactive effects of behavior and local environment.

We heartily invite you to play around with the model code (available at http://www.wsl.ch/info/mitarbeitende/zurell/downloads_EN) and adapt it to your needs. As you will see, the model also allows exploring additional aspects of movement ecology, for example studying movement paths or density-dependent home range structures in more detail.

How can viruses alter the behavior of the hosts? And to what effect? Find out in the Oikos Early View paper “Virus infection alters the predatory behavior of an omnivorous vector” by Candice A Stafford-Banks and colleagues. If you click on the link below, they will tell you all about it in a short presentation.

 

Oikos presentation Stafford-Banks

If invaders do better by early arrival and growing, will native species also benefit from being early? Not necessarily, as found in the Early View paper “Priority effects vary with species identity and origin in an experiment varying the timing of seed arrival” by Elsa E. Cleland and co-workers. Below is their summary of the study and a photo of the students helping out with field work.

Studies show that exotic species differ in phenology (i.e. are active at different times in the season) from the native species in the communities they invade. In Southern California many of our common invaders are exotic annual grasses and forbs that germinate earlier with the onset of winter rains than native herbaceous species. Hence, exotic species might benefit from emerging earlier in the season, allowing them to pre-empt space and other resources to suppress later emerging species, a kind of seasonal priority effect. We tested this hypothesis in an experiment varying the “arrival” time of pairs of species, by placing seeds of focal species into pots of field-collected soil either simultaneously or one week apart. In contrast to our expectations, native species benefited from earlier arrival more often than exotic species. An important implication of this finding is that giving native species a long “head start” likely aids in ecological restoration efforts.

Then, if being active early is so beneficial, why don’t native species have earlier phenology? Isn’t there sufficient selective pressure to favor earlier phenology in native species? Two additional aspects of our experiment support this idea. First, our results show that different species have various strength and even direction of priority effects. In diverse communities where the identity of neighbors will differ among individuals in the population, this could dampen directional selection on phenology. Second, we found that no significant disadvantage to arriving later when compared to being planted at the same time as a competitor. Thus, for native species that tend to have later emergence time than exotic competitors, there seem not to earlier emergence, as this still exposes them to similar levels of competition.

A final aspect of our experiment that is noteworthy; it was planted and harvested by 36 students enrolled in an undergraduate Ecology Lab course at the University of California, San Diego taught by the lead author (the co-authors on this manuscript were the Teaching Assistants for the course). Teaching evaluations and surveys showed that the students enjoyed contributing to original research, and the amount of preparation and oversight necessary to ensure data quality was not much greater than for any of the other lab activities where data were not destined for publication; a clear “win-win” for both the faculty and the students. Hence, our results demonstrate the synergies can arise by merging undergraduate teaching with faculty research programs.

Undergraduate students contributed to this study by aiding in both planting and harvesting. Here they are shown planting seeds for species pairs at the start of the experiment.

 

How pollinator decline affect plant-plant interactions for pollinator is studied in the Early View article ‘Experimental reduction of pollinator visitation modifies plant-plant interactions for pollination’ by Amparo Lázaro and co-workers.

Several studies have indicated a widespread pollinator decline, caused mainly by land-use changes, degradation of natural habitats, fragmentation and habitat loss. Since the majority of plant species are dependent on animal pollination for reproduction, pollinator decline may influence plant reproduction and the persistence of plant populations. However, a pollinator decline may also affect the way plants interact for pollination because these interactions depend on the abundance of plants and pollinators in the community.

To simulate a pollinator decline we set up a novel experiment to reduce pollinator visitation in two communities (one lowland and one alpine) in Southern Norway (see also Lundgren et al. 2013). In the experiment we compared control plots with plots where pollinator visitation had been reduced by means of dome-shaped cages constructed by bending two PVC-tubes diagonally and covering them with fishnet. The fishnet was totally transparent, so flowers were fully visible from outside the net. In order to allow flower visitors inside cages to exit easily, we left an opening between the mesh and the ground, and another opening in the top of the dome. This experiment effectively reduced pollinator visitation without modifying the composition or behaviour of pollinators, or other important biotic and abiotic variables.

Alpine

Lowland

Lázaro et al. (2014) shows that the reduction in pollinators modified plant-plant interactions for pollination in all the six species studied; although for two of them these interactions did not affect seed set. Pollen limitation and seed set data showed that the reduction of pollinator visits most frequently resulted in novel and/or stronger interactions between plants in the experimental plots that did not occur in the controls. Although the responses were species-specific, there was a tendency for increasing facilitative interactions with conspecific neighbours in experimental plots where pollinator availability was reduced. Heterospecifics only influenced pollination and fecundity in species in the alpine community and in the experimental plots, where they competed with the focal species for pollination. The patterns observed for visitation rates differed from those for fecundity, with more significant interactions between plants in the controls in both communities. This study warns against the exclusive use of visitation data to interpret plant-plant interactions for pollination, and helps to understand how plant aggregations may buffer or intensify the effects of a pollinator loss on plant fitness.

What happens with plants, microbes and animals during soli transition from mull to mor? Find out in the Early View paper “Coordination of aboveground and belowground responses to local-scale soil fertility differences between two contrasting Jamaican rain forest types” by David Wardle and colleagues. below is their summary of the study:

There is much interest in understanding how long term decline in soil fertility, in the absence of major disturbance, drives ecological processes, or ‘ecosystem retrogression’. However, there are few well–characterized systems for exploring this phenomenon in the tropics. We studied two types of montane rain forest in the Blue Mountains of Jamaica that occur in patches adjacent to each other and represent distinct stages in ecosystem development, i.e., an early stage with shallow organic matter (‘mull’ stage) and a late stage with deep organic matter (‘mor’ stage). We measured responses of soil fertility and plant, soil microbial and nematode communities to the transition from mull to mor, and assessed whether these responses were coupled. For soil abiotic properties, we found this transition led to declining soil nitrogen and phosphorus, and reduced availability of phosphorus relative to nitrogen; this led to a shorter and less diverse forest. The resulting litter from the plant community entering the soil subsystem contained less nitrogen and phosphorus, resulting in poorer quality litter entering the soil. We also found impairment of soil microbes (but not nematodes) and an increasing role of fungi relative to bacteria during the transition. These results show that retrogression phenomena involving increasing nutrient (notably phosphorus) limitation can be important drivers in tropical systems, and are likely to involve aboveground–belowground feedbacks whereby plants produce litter that is less nutritious, impairing soil microbial processes and thus reducing the release of nutrients from the soil needed for plant growth. This type of feedback between plants and the soil may serve as major though often overlooked drivers of long term environmental change.

Pictures: Characteristic ‘mull’ forest (top left) and uppermost soil layer with significant mixing of organic material and mineral soil (bottom left); and characteristic ‘mor’ forest (top right) with uppermost soil layer consisting of a thick layer of organic matter (bottom right). Over time the ‘mull’ soil transitions to ‘mor soil’, characterized by less available nutrients and reduced availability of nitrogen relative to phosphorus; this in turn has important consequences for the vegetation and quality of litter that is returned to the soil.

 

 

A slug feeding on capsules of the Rough-stalked Feather-moss (Brachythecium rutabulum).

 

 

Herbivores can increase diversity in plant communities by consuming biomass and reducing light competition, thereby benefitting low growing species such as mosses and liverworts (bryophytes). Slugs and snails are important herbivores of forb species and might promote bryophyte diversity if they reduce forb abundance. They also feed on bryophyte capsules, which contain the spores, and it has recently been shown that these spores, can survive the digestive tracts of slugs and snails (endozoochory: internal transport of propagules). Slugs might therefore benefit bryophytes by dispersing their spores.

 

Moss protonema germinated from slug feces in a previous lab experiment (for details see Boch et al. 2013. Fern and bryophyte endozoochory by slugs. Oecologia 172: 817–822).

 

However, whether gastropod herbivory can reduce the dominance of vascular plants and thereby promote the germination and establishment of endozoochorously dispersed bryophyte spores has never been tested experimentally. Moreover, it is unclear whether these possible interacting effects can influence bryophyte species richness. In our study, “Endozoochory by slugs can increase bryophyte establishment and species richness” (Boch et al.) we tested for endozoochorous spore dispersal by slugs (Spanish slug; Arion vulgaris Moquin-Tandon; Arionidae), in combination with sowing of vascular plants, in a fully factorial common garden experiment. We built 30 slug enclosures of 100 cm × 20 cm and introduced either slugs previously fed with the sporophytes of 12 bryophyte taxa, control slugs previously fed with lettuce, or no slugs. We also sowed seeds of vascular plants into half of the enclosures.

 

Experimental setup in the Botanical Garden of Bern with helpers estimating cover values of bryophytes, herbs, and grasses, which then have been averaged for analysis.

 

Twenty-one days later bryophyte cover was on average 2.8 times higher (3.9% versus 1.4%) in the enclosures containing slugs previously fed with bryophytes than in the other treatments. After eight months slugs had substantially increased bryophyte species richness: there were 2.6 times more bryophyte species in the enclosures which had contained the slugs fed with bryophytes than in the other treatments. Sowing vascular plants into the cages did not affect the initial recruitment of bryophytes but after eight months high vascular plant cover did reduce bryophyte diversity. Our findings suggest that slugs are important dispersal vectors for bryophytes and that they can locally increase bryophyte populations and diversity through dispersing spores. They may also act to maintain bryophyte diversity by reducing the dominance of vascular plants.

What is it that determines if a bird should deposit a seed from a fruit in a specific place or not? I the Early View paper “Seed dispersal in heterogeneous landscapes: linking field observations with spatially explicit models”, Jessica E Lavabre ad colleagues combines modelling with empirical studies to find out! Below is the author’s summary of the study.

Frugivorous birds play a critical role in the population dynamics of many fleshy-fruited plants by defining the template for the establishment of new individuals. Because successful germination and subsequent seedling survival is highly dependent upon the micro-habitat where a seed arrives, it is crucial to understand which factors drive seed deposition. In our study, we aimed to take an important step forward in understanding the complex mechanisms that generate the spatial patterns of seed dispersal. Few studies have previously modelled seed dispersal in a real landscape, mostly because real vegetation structure is often highly heterogeneous. Here, we have taken advantage of a simple study system to parametrize mechanistic seed-dispersal models with empirical field data, and we built three models that test three seed-dispersal predictors: distance from the source tree, microhabitat type, and a combination of both distance from the source and microhabitat type.

To our greatest surprise, the third model, combining distance and microhabitat type, did not perform significantly better than the other two, simpler models. Additionally, our results suggested that what we had initially considered as one population could instead be two functionally distinct patches, with distinct seed dispersal dynamics. Altogether, these results reinforce the hypothesis that functionally distinct groups of frugivore species generate scale specific seed rain patterns.

A sexual reproduction system should confer higher mutation rates and hence evolutionary rate than asexual ones. Is it really so? Find out in the Early View paper “Asexual plants change just as often and just as fast as do sexual plants when introduced to a new range” by Rhiannon L. Dalrymple and colleagues. Below is their summary of the study:

Many of the world’s most invasive plant species can reproduce asexually. However, asexuality might be a double edged sword for introduced species. Shortly after introduction, asexual species might have the upper hand because they do not need a partner for promptly increasing in numbers and establishing populations in the new range. Classic theory tells us that sexual reproduction should fuel the processes of adaption through the creation of variation on which natural selection can act. While asexuality may be of advantage in the early phases of introduction, it may lead to an evolutionary dead end.

We measured the rate of changes in multiple asexual species distributed through Australia’s east coast and New Zealand. We have provided evidence that multiple asexual species have undergone rapid morphological changes in response to the novel environments in their introduced range. We then compared the proportion of asexual species that demonstrated a significant change in at least one trait, and the rates at which these changes progressed, to comparable data on sexual species. This was the first test of the difference in potential for rapid change afforded by sexuality, cross species and in the natural world. Our results were astounding: we found no significant difference in the rate or frequency of rapid changes between asexual and sexual species. That is, sex and genetic recombination do not increase the rate or potential for change in this context. Introduction to a novel environment, a population may experience strong selective forces. The new environmental conditions force rapid and significant changes in the phenotype of both asexual and sexual species. It appears that in the process of introduction – it may be adapt or fail, regardless of breeding system.

The most exciting aspect of this study “Increase of fast nutrient cycling in grassland microcosms through insect herbivory depends on plant functional composition and species diversity” (Nitschke et al)- for me – was to take our experiences and results from the field site – the Jena Experiment that was designed for elucidating mechanisms of diversity effects – and to incorporate them into a microcosm experiment under well controlled conditions.

Here, we aimed at tracking the way of nutrients from the intact plant, over an insect herbivore and its feeding characteristics, into the soil, and over to another trophic level – And to judge the role of plant diversity and functional composition along that way.

• Some aspects of the course showed very clearly (e.g. the release of nutrients with feeding and the relevance of the plant functional groups),
• some were surprising (e.g. both throughfall pH and P increased with herbivory intensity and faeces accumulation – diversity having a similar effects, although independently of herbivore intensity),
• and yet others were challenging (e.g. clear soil microbial responses only occurred at high levels of herbivory).

Finally, stepping back a little and taking our field site results into account, formed a broader picture and gave some new perspectives.

Besides the change of perspective the study brought about and the various methods we applied, it was very inspiring and rewarding to work together in a team of people that have realized quite different niches within Biodiversity Ecosystem Functioning-space.

Fig.1 grasshopper rearing

Fig.2 Chorthippus parallelus as model herbivore

Fig.3 plant communities in mesocosm set-ups

Fig.4 growing seedlings for plant communities

Fig.5 mesocosm and sprinkling device

 

Synthesis and integration are critical elements of knowledge synthesis. Using/reusing the work we have already done is a sign of maturation as a discipline, and a very positive step forward to accelerate inquiry by identifying research gaps, opportunities, and effectively summarizing the strength of evidence to date. We are not only poised for potentially profound novel tests of ideas in ecology, evolution, and environmental science, but we are collaborating in news ways, sharing datasets more freely, and more transparently sharing workflows and insights. Oikos supports this movement in all the ways that we can for now and hopefully even more dramatically as we evolve too.  Hence, we are launching a new formal synthesis section for publications.

Meta-analyses and systematic reviews are but two forms of synthesis. Nonetheless, these reviews are currently the most easily aligned with the traditional peer-reviewed ‘publication’ as paper model. This is admittedly a small step, but we need these contributions to inform evidence-based decisions not just for additional research but for management and application. We now have a section devoted to reviews that include quantitative summaries of evidence from within studies or aggregated datasets, i.e. include effect size estimates and appropriate statistics, and also includes systematic reviews that summarize the state of the art of research for a sub-discipline or topic at the scale of studies (i.e. attributes associated with the research, similar to the meta-data of the datasets but without the data from each study listed). We recognize there are many other forms of synthesis that we need to share, and consequently, we will work hard to ensure that we consider these contributions as well (i.e. how to effectively synthesize evidence in all forms, aggregate, and use datasets for novel synthesis).  In handling these papers, similar to all reviews really, we will strive for rapid turnaround, and if sent out for review, we will also work hard to ensure that referees expert in synthesis can provide you with input.

The editorial associated with this section is now OA and online.
Let’s work together to find that big picture.

 

 

 

 

 

Can invasive species actually alter their environment so that more nutrients are available for them? Find out in the Early View paper “Non-additive effects of invasive tree litter shift seasonal N release: a potential invasion feedback” by Michael J. Schuster and Jeffrey S. Dukes. Below is their summary of the study:

Many woody invasive species change their environment to better fit their needs for resources, particularly soil nutrients like nitrogen. One way that they can do this is by accelerating the decomposition of leaf litter—an important step in recycling leaf nitrogen into a form that can be used by plants. However, much of what we know about the decomposition of invasive species’ litters, and their impacts on soil fertility, is based on observations of litter from an individual species decomposing by itself. This is problematic because litters rarely decompose by themselves in nature. More commonly, litters of multiple species are mixed together and decompose more quickly or more slowly than we would expect based on the decomposition rates of each species separately. Thus, we designed a litter bag experiment to examine how the litter of four invasive tree species decomposed differently when mixed with that of four native species, and how this difference might change as the invader became more dominant in the litter layer.

One year and 448 litter bags later, we found some surprising results. Indeed, native-invasive litter mixtures commonly decomposed at different rates than would have been predicted, but whether mixtures lost mass faster or slower than the predicted rate did not follow a strong, consistent pattern. In contrast, the release of nitrogen from these mixtures followed a very clear pattern of being slowed early on, but catching up to or exceeding the amount of nitrogen that would have been predicted at the end of the experiment. Implicitly, native-invasive mixtures were consolidating the release of their nitrogen until later on in the decomposition process, a time that corresponded to the period during which plants, especially the fast-growing invasive species, require the most nitrogen. This pattern was stronger in mixtures comprised mostly of the invasive species and for invaders that produced more nitrogen-rich litter. These findings, in concert with others’ on invasive species and nutrient cycling, led us to suggest that these invasive species might be shifting the release of nitrogen from the litter layer to a time when they are better able to use that nitrogen, and that this might be an important contributing factor to the success of some invasive species.

How are native and non-native-plants affected by various disturbances? Find out in the Oikos Early View paper “Non-native plant species benefit from disturbance: a meta-analysis” by Miia Jauni and colleagues. Below is the author’s summary of the study:

Disturbances, such as fire and grazing, are often claimed to facilitate plant species richness and plant invasions in particular, although empirical evidence is contradictory. Mixed results on the link between disturbance and plant invasions may be partly explained by differences in environmental and methodological factors among studies. To synthesize the literature on how plant species, both natives and non-natives, are affected by disturbances, we conducted a meta-analysis. More specifically, we examined how habitat and disturbance types, and methodological factors (study approach, the spatial and temporal scale of the study) modify the disturbance-diversity and disturbance-abundance relationships. We show that disturbance indeed facilitates the diversity and abundance of non-native plant species in communities where they are already present, while native plant species are less affected. However, the strength of the facilitative impact on non-natives depends primarily on disturbance type and on the measure used (species diversity or abundance), with grazing and anthropogenic disturbances leading to higher diversity and abundance of non-native plant species than other disturbance types examined.

 

Non-native plant species may be able to colonise disturbed patches more efficiently than native species.

How much of nutrients found in a lake actually originate from that lake? And from the surrounding grounds? From the ocean? In the new Oikos paper “Broad sampling and diverse biomarkers allow characterization of nearshore particulate organic matter” Alexander T. Lowe and colleagues study the flux of food across ecosystems. Below is their own summary of the paper:

The flux of food across ecosystem boundaries has important consequences for biological community and ecosystem dynamics. Nutrient poor environments are often subsidized by more productive adjacent habitats. For example, a kelp forest can support animals living in a deep submarine canyon through the transport of dead kelp. In marine and aquatic ecosystems, detritus, or decaying organic matter, produced through photosynthesis is thought to break down and mix into the water. This particulate organic matter (POM) can then be transported long distances by water motion, potentially feeding organisms living far away from the original location of photosynthesis.

 

Researchers from the Friday Harbor Laboratories collect ‘raw’ POM samples. The complex mixture in these jars was dissected using counts and diverse biomarkers. Photo: A. Lowe.

 

The origin of this organic matter is impossible to visually identify once the source has broken down into microscopic detritus. In coastal oceans this food source could come from land or sea. It is therefore common to use biomarkers like stable isotopes or fatty acids to track organic matter through food webs. This type of food source tracking depends on the assumption that each source has a unique biomarker signature that does not overlap the signatures of other potential sources. Using this ‘unique signature’ approach, studies have found high utilization of terrestrial plant detritus in freshwater lakes and coastal marine ecosystems. Similarly, kelp particulate organic matter has been traced into suspension feeders in an array of marine ecosystems. We were interested in the availability of different food sources to organisms feeding on POM. Most studies focus on the consumers, reconstructing the assimilated food sources using mixing models and the unique signatures. This method is often criticized because it does not account for natural variability in the source signatures, which is rarely measured directly. So we took a different approach. We looked directly at the POM to address this question; being a group of ecologists faced with a problem, we tried to count our way out.

 

An example of the complex composition of suspended particulate organic matter. Photo: A. Lowe.

 

Instead of assuming fixed signatures for each source, we made detailed observations of the living and detrital components of the POM and compared them to the stable isotope and fatty acid signatures of same sample. We took advantage of the natural variability of the coastal, temperate environment of the San Juan Islands, Washington, USA to look at food sources available. We expected the distinct seasons to be characterized by variable mixes of riverine, marine benthic and pelagic, and terrestrial sources of productivity. This broad sampling design allowed us to look at the relationships among the abundance of each POM component and the stable isotopes and fatty acid signatures under a range of natural conditions.

 

Nearshore suspended detritus in various stages of decay at Eagle Cove, San Juan Island. Photo: A. Galloway 2012.

 

What we found was 1) a lot of unidentifiable detritus and 2) an incredibly strong correlation among both biomarker methods and the phytoplankton component of the POM. Detrital particles numerically dominated every sample, which meant standard cell counts (especially those that ignore detritus) were potentially missing a big part of the story. So we adapted a point count method to estimate proportions of each category of POM (but did cell counts anyway). Phytoplankton abundance alone explained a lot of the variation in stable isotopes and fatty acids. Incorporating changes in the phytoplankton community explained even more of the variation in biomarker signatures. This signature overwhelmed the non-phytoplankton detritus, implicating phytoplankton as not only a major source of ecologically important fatty acids, but also as a major driver of the variation we see in biomarker signatures. Taking this result a step further we were able to establish the relationship between the proportion of each POM component and the biomarkers often reported to ‘identify’ them. Information that is critical for selecting and interpreting biomarkers. This simple method provided more information about source contribution than the ‘unique signature’ method and allowed us to pick apart the ever-present detritus. We advocate this method as a way to improve the use of biomarkers in complex ecological studies and to start making cross-system comparisons in order to better understand food sources available to POM consumers.

 

Suspension-feeding POM consumers (dominated by Balanus here) in shallow subtidal habitats of western San Juan Island. Photo: A. Galloway 2012.

If you haven’t yet heard the story of the body-snatching parasite lurking among wildflower populations across the globe, you certainly would not be alone. There is no need for alarm – it is a natural part of its ecosystem, and has likely followed its current hosts’ evolutionary paths for millennia. As such, it offers the opportunity to understand ecological, evolutionary, and environmental effects on infectious disease in wild populations, such as those responsible for many emergent infections threatening agriculture, wildlife, and human health. This is what the Early View Oikos paper “Elevational disease distribution in a natural plant-pathogen system: Insights from changes across host populations and climate”  by Abbate & Antonovics is about. Below, is the rest of the summary of the study:

 

Silene vulgaris plants infected with a pathogen that replaces pollen with dark fungal spores. The flowers’ dirty appearance earned the disease its name, “anther smut”.

 

Darwin and Linnaeus were among the first to notice the affected plants with their dirty appearance and altered genders. The tiny culprit, a complex of species-specific fungi in the genus Microbotryum, and its lovely array of flowering Pink Family hosts, has since risen to prominence as a model system for studying everything from genome evolution to how parasites compete for hosts. The fungus works its way through the whole plant and into the flowers, where it takes over the structures that would normally produce pollen (or induces their formation in plants that were otherwise female!) – forcing the plant to produce fungal spores instead. Insect pollinators visit these flowers, whose attractive petals and sugary rewards often appear completely normal, and are tricked into carrying those spores to the next host. As this pollination process is how plants mate, the fungus is essentially a sexually-transmitted infection, behaving epidemiologically similar to diseases of humans or animals driven by either sexual or vector-mediated contact. An infected plant is not killed but sterilized, and has little choice but to keep flowering, year after year, propagating the insidious disease.

 

A bee visits a diseased flower, which is likely still producing nectar. Fungal spores will travel on the bee to the next flower, hopefully (for the parasite) a new host to colonize.

For one particularly widespread host, the bladder campion Silene vulgaris, endemic disease had only rarely been found outside of high-elevation European alpine habitats, despite its weedy presence across the continent. Many diseases are limited to particular habitats within the larger range of their hosts. The most obvious and arguably important example is malaria, which is devastating in the tropics but largely absent from latitudes closer to the poles. Many studies have predicted that as the global climate warms, malaria risk will increase in more densely populated temperate zones, largely in response to shifts in vector distribution. However, others have questioned whether rapid aridification may also reduce risk in currently affected areas with less public health infrastructure. As understanding disease emergence hinges on un-answered academic questions about what factors drive the distribution of disease, we set out to test whether the presence of our little anther-snatcher in Silene vulgaris was similarly limited by environmental factors. It was equally possible that the host populations were simply not as abundant or connected at lower elevations, or that not enough botanists noticed or reported the disease while cataloging plant occurrence.

 

A bee visits a diseased flower, which is likely still producing nectar. Fungal spores will travel on the bee to the next flower, hopefully (for the parasite) a new host to colonize.

To do this, we went to the eastern French Alps, recording host population locations, size, density, and of course, disease. Back in the lab, we were able to use the GPS point of each population to get their proximity to one-another, as well as summaries of climatic conditions. What we found was that indeed, despite being common at high elevations, the disease was exceptionally rare in populations below 1300 meters in elevation. Furthermore, the cool temperatures, high precipitation, and more stable climatic conditions of diseased locations explained this distribution even after correcting for the fact that disease was most common in larger populations, which were relatively more frequent at higher elevations. This study sets up the opportunity to investigate environmental, evolutionary potential, vector distributions, and host resistance effects on the distribution of infectious disease in a natural model species that poses little risk to human health, wildlife, or agriculture. Such studies will be crucial to understanding, and ultimately anticipating, how climatic perturbations may impact disease dynamics and emergence.

 

Janis Antonovics (study author), enjoying an afternoon refreshment along the sampling route in the small alpine village of Les Terrasses, France. Citizens, farmers, and even sheep herders in the local community were always interested in why we were there, and often offered more than just water and lettuce from their gardens – they are a wealth of knowledge on the history, land use, and even biology of their local flora and fauna.

 

A bee visiting diseased Silene vulgaris, complete with visible dark fungal spores at the tips of protruding anthers.

Infected Silene vulgaris at the Col du Galibier, France.

The view of our study area from La Meije glacier near La Grave, France. Pictured: Jessie Abbate (L), lead author; Kerri Coon (R), field assistant and undergraduate researcher.

Shorter (ie, Twitter) version:

Fungal anther-smut disease in Silene vulgaris is restricted to host populations in high-elevation alpine climates.

 

Related website: Field assistant and undergraduate researcher Kerri Coon’s tumbler blog, documenting the 56 days she spent with me in the field tracking some of these populations. 56 reasons to be a biologist: http://kerri-lynn.tumblr.com/

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

How do seabirds use tunas to find more fish? Find out in the Early View paper “Facilitative interactions among the pelagic community of temperate migratory terns, tunas and dolphins” by Holly F Goyert and co-workers. Below is their short summary of the study:

In the Northwest Atlantic Ocean, researchers and fishers have been known to follow flocks of seabirds, particularly terns, in search of Atlantic bluefin tuna, Thunnus thynnus. We wanted to understand whether such “local knowledge” of tern-tuna associations, which has been described but not tested in the literature, is based on quantifiable community interactions. Marine biologists have speculated that these top predators have a commensal (i.e. mutualistic) relationship, such that terns benefit from feeding tunas, which draw attention to “bait balls”, then drive fish to the surface. We found positive, fine-scale, spatial and foraging (e.g. feeding) associations among tunas and terns (common, Sterna hirundo and roseate, S. dougallii), which supports our hypothesis that facilitation drives their ecological and behavioral interactions at sea, where tunas increase prey detectability and accessibility to terns.

 

common terns (Sterna hirundo) observed during a pelagic survey, 27 Sep 2006 (Photo:Marie-Caroline Martin).

The first author, Holly Goyert, observing for seabirds, marine mammals, and tunas during a pelagic survey

That predators affect prey populations and vice versa is well known. But how does the prey’s behavioral responses to predators affect populations of the prey’s prey? This was studied by Bradley Carlson and Tracy Langkilde in the Early View paper “Predation risk in tadpole populations shapes behavioural responses of prey but not strength of trait-mediated indirect interactions”. Below is Bradley’s summary of the study and some photos from the experiment:

It is old news that different populations of the same organism often differ from one another in a number of characteristics. Populations may vary in color, size, morphology, behavior – just about anything. A common cause of such diversity is that populations face different environments that favor different traits. In particular, local predator communities (that is, how many predators there are and what species of predators) can be highly variable and can affect prey behavior. Where predators are abundant and dangerous, prey ought to behave cautiously by hiding, fleeing readily, or being inactive and secretive. When the risk of predation is low, prey ought to pursue opportunities to eat and reproduce.

My doctoral advisor, Tracy Langkilde, and I tested whether populations of wood frog tadpoles (Lithobates sylvaticus) from ponds with high predation pressure showed stronger behavioral responses to predators than tadpoles from ponds with low risk of predation. When they smell a predator in the water, wood frog tadpoles (like many tadpoles) typically become inactive, swimming less and hiding more. We think they’d rather be active so they can consume lots of food, grow large and fast, and turn into frogs before their pond dries. But, if there’s a predator around, it’s more important to not get eaten.

 

Wood frog tadpoles swim in a pond mesocosm.

 

                We selected 18 ponds with wood frogs across Pennsylvania, representing a range of predator communities. Early in the year, I collected freshly-laid wood frog eggs to bring back to the laboratory so I could measure the behavior of the tadpoles. Later in the year (when tadpoles were swimming in the ponds), I used a net to collect random samples of animals from each pond. I’d then sort through the contents of the net to count the number of each kind of predator I found. These included dragonfly nymphs, newts, and other salamanders and insects. These data were used to assign each pond a value for how high the predation risk was; the more predators, and the more ‘dangerous’ these predators, the higher this number would be.

Brad Carlson uses a dipnet to sample a pond community.

                But what about those eggs I brought back to the laboratory? We hatched them into tadpoles at a research farm at Penn State University and, when the tadpoles were old enough, introduced them to pond mesocosms. Pond mesocosms are artificial ponds, smaller than most natural ponds but big enough to be reasonably realistic environments. Our mesocosms were created by filling large cattle-watering tanks with water and adding standard amounts of dead leaf litter. We also added a small amount of pond water, introducing bacteria, algae, and other microorganisms which flourish and create functioning ecosystems. Each pond that we collected eggs from was represented by two of the mesocosms. One mesocosm had a cage floating in it, which contained a dragonfly nymph (Anax junius), voracious and hardy tadpole predators. Regularly feeding the dragonflies extra tadpoles in these cages ensured that the mesocosm water smelled of danger but that the experimental tadpoles wouldn’t actually be eaten. The other mesocosm served as a control (with an empty cage), allowing us to measure the normal, ‘baseline’ activity levels of these tadpoles. After a few weeks, I measured how active the tadpoles were by quietly walking around the mesocosms and counting how many tadpoles I could see (their ‘visibility’) and how many of those visible tadpoles were moving rather than still (their ‘movement rate’).

Brad Carlson observes tadpole behavior in mesocosms.

Our analysis revealed that tadpoles from ponds with higher predation risk responded more strongly to predators than tadpoles from other ponds, spending less time visible, and slightly tending to move less. A good explanation for this pattern is that tadpole behavior is adapted to local environments, with generations of selection in high predation environments ensuring strong responses to predators. This is interesting in its own right though not too surprising. What we really wanted to know was whether this kind of variation in tadpole behavior affects the pond ecosystem. In particular, antipredator behavior often leads to trait-mediated indirect interactions (TMII). In this case, the TMII is an effect of the presence of a predator (dragonfly) on the tadpole’s own food (periphyton, a film of algae and other microbes and detritus growing on submerged surfaces). Dragonflies shouldn’t directly interact much with periphyton, but they should indirectly via their effect on a trait of the tadpoles – foraging activity. If dragonflies cause tadpoles to be less active and thus eat less food, then their food (the periphyton) should increase in abundance. We expected, therefore, that populations of tadpoles that respond strongly to predators should produce larger increases in periphyton than less responsive tadpoles.

Pieces of filter paper with collected samples of dried periphyton (green and brown matter) from tadpole mesocosms.

 

To test this we simply measured the mass of periphyton in the mesocosms by removing tiles we placed in their, scraping off the periphyton, and weighing it after drying. We found that, as expected, mesocosms with caged predators had much higher biomass of periphyton. However, the amount that periphyton increased when adding predators didn’t depend on how strongly the tadpoles responded to predators, nor did it depend on the predation risk in the pond from which the tadpoles came. In fact, tadpole behavior overall was a generally poor predictor of the amount of periphyton in the mesocosms.

This was unexpected, as we established a clear mechanism by which periphyton increases with predators (dragonflies decrease tadpole activity, decreased tadpole activity increases periphyton). Apparently, the amount the tadpoles actually eat is not perfectly linked to their activity: some tadpoles may become very inactive when predators are introduced, but still consume as much food as tadpoles that barely respond to predators. Do they switch their diets, or eat while hiding in refuges, or do most of their foraging at night? And, are tadpoles from ponds with more predators better at compensating for lower activity levels? These questions and more still remain, and will help us as we continue to try to understand how variation in behavior can impact ecosystems.

How carbon moves from terrestrial food-webs to aquatic ones are studied in the new Early View paper “Boomerang ecosystem fluxes: organic carbon inputs from land to lakes are returned to terrestrial food webs via aquatic insects” by K. Scharnweber and co-workers. Below is their summary of the study:

The TERRALAC-project (http://terralac.igb-berlin.de/) ran from 2010 to 2013 and was an interdisciplinary project, based at the Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany in collaboration with University of Potsdam and Technical University Berlin. Five PhD students worked in five subprojects. The overall aim of TERRALAC was to study the effects of terrestrial particulate organic carbon (tPOC) on shallow lake ecosystems. We wanted to find out, how terrestrial leaves that enter lakes in autumn are actually processed with the lake food webs and we wanted to test this on the natural spatial scale.

One prominent obstacle in studies on the effects and contribution of this allochthonous carbon on lake food webs is the problem of overlapping isotope values of the potential resources. Isotope signatures of the terrestrial carbon are often very similar to those of aquatic primary producers. TERRALAC chose a novel approach by using a tPOC tracer that is isotopically distinct, but also similar to the size and structure of natural leaves: maize (Zea mays) leaves.

Photo 1: Maize added into the littoral zone. The rope prevents it from floating into the open water.

In October 2010, we divided two small and shallow lakes, located in the rural area of Northern Germany approximately 100 km north of Berlin, in two equal halves. Both lakes are eutrophic and of similar size and depth. However, they have different alternative stable states: Gollinsee has turbid water and is dominated by phytoplankton, whereas Schulzensee has clear water and is dominated by macrophytes. We used plastic curtains to divide the lakes (Photo 1) from surface to bottom. With the help of many hands, we added the maize leaves into the littoral zone of the treatment sides of the lakes (Photo 2,3). By this approach we tried to mimic the natural input of tPOC by leaves in autumn.

Photo 2: Maize addition by hand in Schulzensee (October 2010).

Photo 3: Installation of the plastic curtain in Gollinsee.

Photo 4: Emergence trap used in our study.

In our article we present the flow of terrestrial carbon to lakes and back to its terrestrial surroundings via emerging insects (Figure 1). We focused on Chironomidae that have an aquatic-terrestrial life cycle and collected them as larvae, but also as adults using emergence traps (Photo 4). After emergence, they are known to become prey for terrestrial predators, for example for spiders that live in the riparian reed belts. Carbon isotope values of Chironomidae and spiders were significantly elevated in the lake treatment sides as compared to reference sides. As further demonstrated by isotope mixing models, contribution of maize was higher in Schulzensee, the lake where macrophytes are present. We conclude that structural complexity provided by the macrophytes may trap the leaves and by that enhance the food availability for the larval Chironomidae. In summary, we present the tight linkage between aquatic and terrestrial habitats and the cycling of organic matter across boundaries and borders.

 

 

 

 

What is climate change doing to plant–pollinator interactions? In the last decade, ecologists have focused on the possibility that climate change will shift the seasonal timing (phenology) of plants relative to their pollinators, reducing temporal overlap between interdependent species. In the Early View paper “Plant–pollinator interactions and phenological change: what can we learn about climate impacts from experiments and observations?” in Oikos , I evaluate the evidence that plant–pollinator overlap is changing as a result of climate change, and that such changes affect population persistence. I also discuss the strengths and limitations of different types of evidence for climate-change impacts. In particular, I explore the challenge of interpreting “temporal transplant” experiments, which manipulate the phenology of a subset of plants or pollinators in isolation, creating subpopulations of mistimed individuals in a matrix of unaltered phenology.

Observational data have shown us that, for the most part, plant and pollinator phenologies are advancing in parallel in response to warmer temperatures. While there are cases of plants blooming before their pollinators are active and consequently setting few seeds, there is no conclusive evidence yet that climate change is causing this “mismatch” to happen more often. There’s even less indication that pollinators are suffering from mismatch with plants—but pollinator fitness has received much less study. I suggest that there is much still to be learned about the direct effects of climate change (e.g., snowpack reductions, temperature extremes and fluctuations) on populations of pollinators and pollinator-dependent plants—effects that might be more demographically consequential than non-parallel shifts in phenology.

By Jessica K.R. Forrest

Photo of male Megachile on unopened flower head of Erigeron speciosus. © J. Forrest

Many animals are breeding earlier and earlier in response to a gradually changing climate – but what happens when a species encounters a dramatically different climatic regime such as a complete reversal of the summer-winter rainfall pattern? In our article,  “Phenological shifts assist colonisation of a novel environment in a range-expanding raptor”, we explore this question by investigating how variation in the timing of breeding and breeding success of black sparrowhawks Accipiter melanoleucus relates to weather patterns during their colonisation of the Cape Peninsula of South Africa.

Heavy rain can have pronounced effects on breeding success in raptors, flooding exposed nests and potentially impairing the ability of parents to hunt. In the eastern and north-eastern areas of South Africa the majority of rain falls in the summer months and black sparrowhawks breed during the dry and relatively cool winter. During the last half a century a number of bird species have gradually expanded their range south-westwards within South Africa bringing them into contact with a dramatically different weather pattern: in the south-western regions the rain falls mainly during winter, a complete reversal of what occurs elsewhere in their range.

In the 1990s, the first black sparrowhawks were recorded breeding on the Cape Peninsula, in the shadow of the iconic Table Mountain. Rising to over a 1000m, this huge lump of sandstone generates exceptionally high levels of rainfall in the immediate lee of the prevailing winds, during the winter months as deep depressions roll in off the Southern Atlantic Ocean.

In 2001 a long-term study of the black sparrowhawk population[http://blackspar1.wordpress.com] on the Cape Peninsula was initiated. In the first year fewer than a dozen nests were monitored but as the population expanded so did the project. A team of dedicated volunteers now follows the breeding success of over 50 nests each year. This hard work has generated a fantastic data set with which to explore how the unusual weather of the Cape Peninsula affects breeding phenology and the role that shifts in breeding phenology has played in the growth of this population.

We found that black sparrowhawks on the Cape Peninsula commence breeding up to three months earlier than eastern and north-eastern populations, and that breeding was suppressed during the months of heaviest rainfall. Earlier breeding attempts also produced more chicks. As a result of the shift in timing of breeding, the probability of population extinction was reduced by 23%, suggesting that this phenological shift could have assisted the colonisation of the Cape Peninsula. However contrary to expectations we found no strong evidence that black sparrowhawks were responding to local variation in rainfall within the Peninsula study area. We suggest that shifts in breeding phenology may be driven in part by other novel processes encountered during colonisation, such as interspecific competition for nest sites and lower temperatures during late summer than is the case in the rest of their range.

Clearly there is more to learn about how black sparrowhawks cope with the differing environments they encounter as they have spread westwards. Looking forward, PhD student Gareth Tate is using nest cameras and satellite tracking technology to investigate in further detail how weather influences hunting behavior.

The Authors through Arjun Amar

 

Papers published in Oikos should meet the principal criteria to generate synthesis in ecology. Synthesis can be created in different ways and definitively obtained when long-term data sets, novel analytical tools and good hypotheses are merged. The first editor’s choice for the June issue is the paper by Karen Lone and colleagues on multi-predator landscapes of fear. Motivated by challenges to manage large carnivores in Scandinavia in relation to human conflict, the authors used an extensive dataset containing Lidar data, behavioural data and hunting information to demonstrate the interactive impact of multiple predators on predation risk of a single prey species. By means of this integrative approach, the authors demonstrate a predation risk from humans and lynx on roe deer in areas with a high vegetation cover, but an additive impact in more rocky locations. As such, the study demonstrates the complexity of predator-prey interactions in real landscapes, and clearly emphasises the need and value of individual-based ecology to understand interactions in (simplified) foodwebs.

Oikos has decided to highlight meta-analysis papers because of their principal role to create synthesis in ecology.  Chris Lortie will be Editor-in-Chief for this category of papers (look out for his editorial in the August issue). Meta-analysis papers will be published OA for three months after publication. Ward and colleagues tested the performance of time-series forecasting models for natural animal populations based on more than 200 datasets of vertebrate surveys. Such a meta-analysis is considered essential because of the increasing demand to forecast population dynamics under different global change scenarios. While forecasting approaches using non-mechanistic statistical models have greatly evolved the last decades in population biology, still a limited amount of such models are commonly used. By performing a statistical competition experiment, the authors tested the predictive performance of 49 different forecasting models and found simple models to behave well after all, although increasing model complexity fitted time series better in case of species with cyclic population dynamics.

Editor’s choice papers are free online for three months!

The ants underfoot forage faster as the ground warms each day. Likewise, the fish in nearby streams and the worms and other organisms that parasitize these fish speed their activities as the water warms. Above the stream, dragonflies engage in more aerial battles each hour for prime perches as the air warms. We have all witnessed these quickenings, as insects and other ectotherms, organisms whose body temperature are primarily environmentally determined, become more active and interact more quickly in hotter environments. How much faster do such biotic interactions increase with temperature, and why?  This is studied in the Early View paper “Rates of biotic interactions scale predictably with temperature despite variation” by Bill Burnside and co-workers. Their sumary of the study continues here:

Anderson Mancini, Creative Commons – Flickr

 

In this meta-analysis, we look across taxa and habitats to assess the temperature dependence of biotic interaction rates, such as herbivory and competition, between two species. We hypothesize that these rates will increase approximately exponentially with temperature, mirroring the temperature dependence of respiratory metabolism generally. This hypothesis is inspired by the metabolic theory of ecology, which suggests that many ecological patterns and processes are functions of individual metabolic rates of the organisms involved. These rates vary characteristically with body temperature, which affects the rates of cellular chemical reactions. Biotic interactions are metabolic because they involve exchanges of energy and materials between organisms and their environment and because they are inspired by basic metabolic demands, like the need to eat.

Matthew Britton, Creative Commons – Flickr

 

This work was intriguing because even though we were not interacting ourselves with all the amazing organisms in our analysis, like those pictured here, we did not know what we would find. The studies were often focused on a related question and just happened to include temperature as a variable or did not include graphs, so it was tough to visualize how some rates varied with temperature. And the rate terms varied by their nature, from the rate ground beetles catch and eat fruit flies to the rate sea lice parasitize fish.

Watershed_Watch, Creative Commons – Flickr

 

Seeing the results for the first time—the generally parallel lines, each with a slope indicating how interaction rate scales with temperature—was amazing. Our results generally supported our hypothesis, but there was also a great deal of variation. We could only find a fairly small sample of studies on most interaction types, which probably accounts for some of this variation, but organisms vary in their level of thermal performance and peak response, among other traits, which surely accounts for variation when different species interact.

Understanding how temperature affects biotic interaction rates is more important than ever in our warming world. The answers won’t be entirely straightforward and may vary among places, species, and communities, but this study offers basic insight to inform our search. 

Vernal pool ecosystems emerge from winter and spring rains that fill shallow depressions in the earth, resulting in small patches of wetlands spread throughout the Central Valley of California, USA. These pools act as a crucial habitat for a diverse community of annual plants, many of which are endemic to the region. Many of these species complete the majority of their entire lifecycle within the short duration that the pool exists. As the standing water evaporates, a stunning array of wildflowers is produced from the plant species that co-occur in these temporary ecosystems. The endemic diversity of these pools, coupled with the short lifespan and small size of the species, makes them an ideal model system for testing questions of community assembly. In the study “Functional trait differences and the outcome of community assembly: an experimental test with vernal pool annual plants” in Oikos, Nathan Kraft, Greg Crutsinger, Elisabeth Forrestel and Nancy Emery measured functional trait differences between species in the pools and tested whether these characteristics could be used to predict the outcome of interactions among plant species and, ultimately, the processes structuring the vernal pool communities.

Kraft and colleagues used a greenhouse experiment with eight different annual vernal plant species and grew them together in all pairwise combinations, so that every species had a chance to interact with every other species. They also submerged these combinations in tubs of water for different amounts of time to mimic growing at different depths in a vernal pool. Prior work in this system has found that the recession of water in the spring generates a gradient of species composition along the sides of vernal pools. The authors observed that plant species tended to do better when they had larger leave size, lower specific leaf area (fresh leaf area divided by dry leaf mass), and greater investment in lateral canopy spread than their neighbors. It also turns out that not all individuals within species are equal in these interactions. The authors took an additional step relative to many trait-based studies and measured functional traits for all individuals in the experiment. Models that incorporated individual trait differences did a better job of predicting the outcome of the interactions than models using only species average trait values.

The results of this study suggest that plant traits can be used to help understand the outcome of interspecific interactions in vernal plant communities. It’s also clear that individual trait differences matter. If resources allow, researchers can boost their predictive power by considering trait differences among individuals, instead of focusing on the average traits for different species, which has been the standard practice. There is still more work to be done to understand how vernal pool communities are assembled, as the patterns Kraft and colleagues observed in greenhouse did not strongly match patterns seen in natural pools, suggesting other undiscovered factors are also contributing to species distributions. Ongoing work from Nancy Emery and others will continue to shed light on the processes structuring these fantastic communities in the near future!

How do plants react to seasonal extremes? Find out more in the new Early View paper “Leaf and stem physiological responses to summer and winter extremes of woody species across temperate ecosystems” by Elena Granda and co-workers. Read Elena’s summary of the study here:

Our paper presents evidence that winter stress in the temperate region is more extreme than summer for forests that do not experience summer droughts, but also for those where summer drought combines with winter freezing. In this study we compiled existing literature to identify overall trends of the impact of seasonal extremes on plant performance (leaf and stem physiological responses). We further compared the general patterns over the temperate region with a continental Mediterranean case study subject to intense summer droughts and winter freezing.

Continental Mediterranean and riparian forests at Alto Tajo Natural Park (Spain) during a) summer drought and b) winter freezing

 Although it is known that winter cold limits plant performance, as is also the case for summer drought in dryland ecosystems, our study revealed that across temperate forests: (i) winter is commonly an equal or even stronger stress than summer, including particular cases of Mediterranean vegetation; (ii) many species are able to maintain stomata open during winter, favoring carbon gain over most of the year; (iii) stomatal conductance and xylem hydraulics show a coordinated seasonal response at sites without summer droughts, and (iv) deciduous angiosperms are the most sensitive to climatic stress.

These results suggest that the differences among functional types in seasonal dynamics of physiological performance are strong enough to advocate their importance in determining ecosystem productivity throughout the year, especially in ecosystems where carbon gain is limited to a few months. These patterns present a baseline against which to compare shifts for key plant species and communities with ongoing climate change.

Bird pollination in Europe? Really? Well, find out in the Early View paper “Flower visitation by birds in Europe” by Luis P da Silva and co-workers. Below is Luis summary of the paper:

Birds are among the most studied animal groups and are most likely the one that attracts more general public attention. These winged animals, are known throughout the world for their interactions and coevolution with plants. They are known to be very important for several plant groups, providing seed dispersal and promoting sexual reproduction through pollination.

When anyone hears about birds pollinating plants, their first thoughts go to hummingbirds, which are very specialized bird pollinators that are able to hover. However, there are other bird groups that are not considered so specialized in pollination (and unable to hover), but well known to pollinate plants, as the honeyeaters. This bird group, somewhat specialized in taking nectar and consequentially pollinate flowers, are present in almost all over the world, except in Antarctica and Europe. If in Antarctica that is not unexpected, in Europe (and actually in almost all the Western Palearctic) that seems a little odd, that how such ubiquitous and abundant food source is not recognized to be regularly exploited by any bird species. With this, insects are often considered the only ecologically relevant pollinators in Europe. Nevertheless, generalist birds are also known to visit flowers and in some cases to successfully pollinate plant species around the world.

In Europe there are several scattered publish records of flower visitation by birds. We carried out a fine literature search and compiled our own observations to estimate the extent, richness and ecological relevance of this mutualistic interaction. These interactions were not only of direct feeding observation, but also from pollen found attached to feathers, in faeces and stomach contents. We found that 46 bird species visited flowers of at least 95 plant species, 26 of these being exotic to Europe, yielding almost 250 specific interactions inside Europe. Additionally, we registered four more European bird species interacting with 12 different plant species outside Europe. Despite these numbers, only six plants species, both native and exotic, were confirmed to be efficiently pollinated by birds in Europe. We argue that the ecological importance of bird-flower visitation in Europe is still largely unknown, particularly in terms of plant reproductive output. We suggest that nectar and likely pollen are important food resources for several bird species, mainly during winter and spring, especially for tits (mainly Cyanistes), Sylvia and Phylloscopus warblers. The prevalence of bird flower-visitation, and thus potential bird pollination, is slightly more common in the Mediterranean basin, which is a stopover for many migrant bird species, which might actually increase their rule as potential pollinators by promoting long-distance pollen flow. We argue that research on bird pollination in Europe deserves further attention to explore its ecological and evolutionary relevance.

Different factors that effect predation in marine habitats are explored in the Early View paper “Differences in predator composition alter the direction of structure-mediated predation risk in macrophyte communities“ by Simone Farina and co-worker’s. Below is Simone’s short summary of the study as well as a reflection on the history that lead to the study.

Using sea urchins as model prey we examined the role of structural complexity in mediating predator-prey interactions across three bioregions: Western Mediterranean Sea, Eastern Indian Oceanand Northern Gulf of Mexico. As expected biomass of the habitat structure and fish predator abundance were the main determinants of predation intensity. Interestingly though, the direction of structure-mediated effects on predation risk was markedly different between habitats and bioregions. In Spain and Florida, where predation by fish was high, structure served as critical prey refuge, particularly for juvenile sea urchins. In contrast in Western Australia predation was generally higher inside the structure where bottom predators were more abundant.

Gallery 1: Meditarrenean Sea

In this sense, as a Mediterranean student I will never forget the days of field work in WA. We had to look for Heliocidaris erythrogramma, the Australian model prey, the equivalent of Paracentrotus lividus in the Mediterranean Sea, and it was like looking for sparrows in the Amazon rainforest. Kelp was full of huge gastropods. Every time I moved a few shoots I had the impression of seeing any kind of tail run away quickly. It was very easy to get distracted from my search. One time we found a huge Coscinasterias calamaria (sea star) remained attached to a fishing line used to mark one of the sea urchins after having swallowed it entire. In seagrass ecosystems (Amphibolis griffithii and Posidonia sinuosa) we observed many little and coloured sea stars (Patiriella brevispina) approaching day by day to our sea urchins and finish them one after the other. In Australian seagrass ecosystems, working to head down supposed some time to have a look around to check for unexpected arrivals of huge sting ray, as ufos flying over a landscape. Macrophyte communities that we explored in Australia are totally different from the Mediterranean ones, so it does not surprise me that structures works in different ways. It was a really pleasure to carry out this experience and I think I’ll have a good story to tell my grandchildren.

Gallery 2: Australia

By comparing fish communities with bird communities Kirsten Nash an co-workers assess the appropriateness of different size distribution indices used in a variety of studies. The analyses resulted in the Oikos Early View paper “Habitat structure and body size distributions: cross-ecosystem comparison for taxa with determinate and indeterminate growth”. Below is the author’s own summary of the paper:

How the study arose:

The study resulted from conversations at the working group ‘Understanding and managing for resilience in the face of global change’, hosted and funded by the USGS Powell Centre for Analysis and Synthesis in Fort Collins, Colorado (https://powellcenter.usgs.gov/). The working group came about through a chance meeting between myself and one of the other authors of our study (Shana Sundstrom) at the 2011 Resilience Conference in Arizona. We were both starting our PhDs addressing similar questions but in different ecosystems: Shana primarily focuses on birds, whereas my research looks at coral reef fish communities. Participants in the working group come from Canada, USA, Sweden, South Africa and Australia.

Photo of the ‘Managing for resilience’ working group at the USGS Powell Centre in Fort Collins, Colorado:

Description of our group’s focus and short summary of the paper:

An ecosystem can be in a number of different forms or states, such as a reef covered in many corals vs. a reef with large areas of thick algae and little coral. The ability of an ecosystem to remain within its initial form (e.g. coral reef) when impacted by disturbances resulting from rapid global change, rather than shift to another state (e.g. algae reef), is called the resilience of the ecosystem. Until recently, a lot of the work that has looked at the resilience of ecosystems has been theoretical. Our working group focuses on putting this theory into more practical terms, i.e. understanding how likely is it that the ecosystem will remain in its current form over time, as this directly affects natural resources on which we rely for food, water, etc.

 

An important step in this process was to take methods that had initially been developed to look at terrestrial taxa, and explore their appropriateness for marine systems, to ensure that our work was relevant across a range of ecosystems and wasn’t limited to terrestrial studies. The result was our study recently published in Oikos, where we compare the ability of different animal size measurements to highlight the effect of a variety of habitats on the bird and fish communities that live within them. We completed fieldwork on fish communities inhabiting reefs of the Great Barrier Reef and the Seychelles and used published data for bird communities in Borneo (Cleary et al., 2007, Ecological Applications) and the Lofty Ranges, Australia (courtesy of Hugh Possingham and the Nature Conservation Society of South Australia). The study shows that both average and individual size measurements are useful for showing the effect of habitat on bird communities. In contrast, for fishes, we need to incorporate the size measurements of all individuals within a community to show the effects of habitat on fishes.

 

 

An open future for ecological and evolutionary data?
Amye Kenall*, Simon Harold and Christopher Foote
doi:10.1186/1472-6785-14-10

A very succinct and accurate editorial on the future directions needed for data sharing in ecology & evolution was recently published at BMC Ecology. The key issues for ecology & evolution were identified and included the following:

Opportunity cost: available data reduces costs, provides opportunities, and serves local stakeholders

Shared benefits: new forms of collaboration, discovery, and accelerated synthesis will emerge

Blood, sweat and tears: long-term datasets are hard won and it is difficult to let them go (public)

A bigger picture: macroecology and other relatively new ways of doing ecology need open data

Data management: metadata is critical, always, and for ecology/evolution in particular because the ‘lab’ is often outdoors

Credit where credit is due: many new reputation economy tools and reward systems are in place to serve as incentives for all scholars not just for ecology and evolution

Transparency and trust: we review the manuscripts of others, why should datasets be free from scrutiny?

Each issue is well described. The one that clicked the most for me was the ‘blood, sweat, and tears’ argument as I have heard it made by many ecologists. Fieldwork can be grueling.  We also hope that we will reuse our own datasets many times. However, I suspect that we do not. Let them go free. As a personal goal, I have mentioned the idea of #ecodataweek on twitter as a good push to myself via a bit of friendly competition to get stuff out there more too.

Oikos also partners with Dryad, and I hope that this editorial likewise inspires you to publish your data.  I would also love to see a more in-depth set of analyses for Oikos readers on these topics and how they relate to the journal mission of ‘novel synthesis’ and synthesis science in general.

Additional resources to consider:
1. DataONE for data management planning tools and a list of best management practices for data documentation (pdf link is best).
2. A good read on how our discipline has likely crossed into the realm of big data.
3. The pivotal nature of data sharing to the future of publishing in ecology.
4. Re-read the file-drawer problem papers such as the Csada et al. 1996 Oikos paper on the topic (classic for ecology but still feels modern with issues of limited OA and accessible data).

 

 

 

“Nature is much more complicated” than predicted in theoretical  models. In the Early View Paper “Matrix models for quantifying competitive intransitivity from species abundance data”, Werner Ulrich and colleagues try to fill a gap between models and mother nature when it comes to competition interactions.

Below is their summary of the study:

Ecologists have devoted much effort to inferring competitive processes from observed patterns of species abundances, morphology, and particularly from changes in the spatio-temporal distribution, (i.e. species co-occurrences). Classic assembly rules models, derived from the principle of competitive exclusion, predict that differences in competitive abilities should cause non-random patterns of species occurrences among sites and generate inequalities in species abundances within sites. Competitively inferior species are predicted to occur less frequently and at lower abundance, and an important and largely unresolved question is how such species can persist in a community over long time periods (also known as Darwin’s paradox and nicely explained in http://www.wbez.org/blog/clever-apes/2011-11-22/clever-apes-22-paper-covers-rock-94295) .

Simple competition models assume that species can be ranked unequivocally (A>B>C…>Z) according to their competitive strength. However, nature is much more complicated and intransitive competitive networks can generate loops in the competitive hierarchy (e.g. the rock-scissors-paper game, in which A>B>C>A). Importantly, such loops allow weak competitors to coexist with strong ones. Additionally, the structure of such loops might be modulated by environmental factors. Experimentally competitive strength can be tested with simple two-species systems. Testing competitive interactions in many-species systems requires an increasing number of species exclusion experiments.

Up to now no comprehensive theoretical framework existed to infer competitive loops from observed patterns of species abundances. Existing mathematical models based on presences and absences of species (on perfect competitive exclusion) have rarely been applied to empirical data. Our new paper in Oikos seeks to fill this gap in our knowledge. We introduce a statistical framework for evaluating the contribution of intransitivity to community structure using species abundance matrices that are commonly generated from replicated sampling of species assemblages. We use a stochastic back-engineering procedure to find a transition probability matrix that predicts best observed distributions of abundances in an ordinary Markov chain approach. We then use a probabilistic argument to convert this transition matrix into a pairwise competition matrix that contains the information of competitive strength between all species in the community. Our approach can be used for abundance data, time series, and abundances in combination with environmental data. Our case study on necrophagous flies and their hymenopteran parasitoids revealed strong hints towards instable competitive hierarchies. In other words the competitive outcome in these communities (having at least five species) strongly depended on environmental conditions but also on the spatial structure of fly and parasitoid occurrence.

We hope that our new approach sparks a fresh new look at competitive interactions in ecological communities and helps to assess and appreciate the importance of intransitivity for the coexistence of species in natural communities. We fell the need for joint approaches that link existing methods using the temporal and spatial co-variation in species abundances and occurrences with methods (like our) that reconstruct competitive hierarchies. 

Bimodality – the characteristic of a continuous variable having two distinct modes – is of widespread interest in data analysis. This is because, in some cases, we can use the presence or absence of bimodality to infer something about the underlying processes generating the distribution of a variable that we are interested in studying. In ecology, tests of bimodality have been used in many different contexts, such as to understand body size distributions, functional traits, and transitions among different ecosystem states. But a lack of evidence for bimodality has been reported in many studies. Our paper “Masting, mixtures and modes: are two models better than one?”, now shows that a widely-used statistical test of bimodality can fail to reject the null hypothesis that focal probability distributions are unimodal. We instead promote the use of mixture models as a theory oriented framework for testing hypotheses of bimodality.

Our interest in this problem arose with the publication of Allen et al. 2012 Oikos 121: 367–376. The paper impressive synthesised 43 years of seeding patterns in a New Zealand mountain beech Nothofagus forest. Seed production in these trees is interesting because a population can go several years without reproducing and then all the individuals in a population will do so. Such intermittent and synchronous reproduction is also known as mast seeding.

 

Dense Nothofagus forests (dark green) dominate mountain-sides in Fiordland, New Zealand

 

In their paper, Allen et al. tried to infer the importance of resource limitation in driving mast seeding patterns by describing various characteristics of seed production. A key finding was that they could not reject the null hypothesis that the distribution of annual seed production was unimodal using an empirical calculation known as Hartigan’s dip test. Allen et al. 2012 concluded that few studies could ‘robustly test for bimodality’ because they lacked ‘long time-series’ and used questionable methods.

 

Nothofagus solandri var. cliffortioides trees in Fiordland, New Zealand

The bimodality result inspired a lot of reflection. We were interested in why we might consider an annual count that takes values larger than zero at more than 2 year intervals to ever even present two modes. Populations should only have one mode because the single most frequently observed seed count will be relatively low, on average, in most years. Thus, plants can never be bimodal when a single distribution is fit to seed counts – even if they alternate annually, on average, between the absence and presence of seed production. This is because of the underlying statistical nature of seed counts, which we describe in further detail in our paper.

Stepping back further from the problem, we began to realize that there is a need to consider multiple probability models, each with at least one unique mode, where plants flower at >2 year intervals.We illustrate these ideas by analysing 37 years of data from five grass species in New Zealand. Critically, we found clear evidence for bimodality using mixture models that associate distinct probability distributions with medium- and high- versus non- and low-flowering years. We expect these patterns to be driven by different processes and hence, modelled by different probability distributions. We found no evidence for bimodality with Hartigan’s dip test that assumes a single probability distribution can be fitted to all the data. Our findings show the importance of coupling theoretical expectations with the appropriate statistical tools when predicting the responses of ecological processes.

 

Snow tussock Chionochloa rigida flowering in Fiordland, New Zealand

The authors through Andrew J. Tanentzap

Talk about choosing between pest and cholera! A bird on migration, has a tough job, and with a virus infection in the body, the job is even worse! In the early View paper “A tradeoff between perceived predation risk and energy conservation revealed by an immune challenge experiment”, by Andreas Nord and co-workers.

Below is Andreas summary of the study:

Birds, like man, must maintain a high and even body temperature to function properly. This is a challenging task, not least in winter when the internal temperature may be some 50-60 °C above that of the surroundings. It is not surprising that this challenge requires high food intake. In fact, a blue tit, which is a common garden and forest bird across Europe, must sometimes put on 10 % of their body weight as fat on a daily basis during cold winter days. A human of average weight would have to eat some 200 hamburgers to ingest the same amount of fat.

As if this was not enough, the time of peak food demand often coincides with the time when food resources are the most difficult to obtain. To overcome such hardships, many animals actively reduce their body temperature at night (nocturnal hypothermia), a process that substantially lowers their energy demands. Yet the use of nocturnal hypothermia is often not enough to avoid the risk of starvation, because the demands from other body functions compete for the same fat reserves. In these situations, birds may have to prioritize surviving the night by reducing the use of other costly functions, such as the immune defense system. In other words, because food availability is limited in winter, it may not be possible to maintain sufficient amounts of body fat at the same time as an adequate defense against invading pathogens.

This was the subject for our study, in which we investigated how an activated immune defense system impacted on the use of nocturnal hypothermia and behavioral strategies for minimizing energy expenditure in wild blue tits in southern Sweden. Contrary to our expectations, an immune response did not cause birds to change their use of nocturnal hypothermia, which could indicate that any energy costs of the immune defense system are not large enough to interfere with energy conservation processes. However, birds with an ongoing immune response showed a different behavior compared to healthy birds, which was manifested as an increased use of sheltered roosting sites when the immune response was at its peak. Using such roosting sites often confers energy savings, because birds are less exposed to wind and temperatures are higher than those outside. However, sheltered roosts often come at the expense of increased predation risk, because these roosts may be easier to locate and escape prospects are typically relatively low upon detection.

We interpret this increased risk taking behavior in sick birds as consequences of a higher need to exploit the energetic benefits of sheltered roosts. Because this required birds to accept a higher predation risk at night, our results may indicate that energy stress from less efficient thermo-regulation poses a higher mortality risk for sick birds than does any predation risks pertaining to sheltered roosting sites. This was not the case for healthy birds, whose thermo-regulatory capacity was not impaired by an ongoing immune response. These birds instead actively avoided sheltered roosts, because their main source of overnight mortality might indeed have been the risk of predation.

Natal dispersal is a complex process but what could be the role of endo-intestinal parasites in dispersal propensity, distance and date of departure? In our article “Parasite abundance contributes to condition-dependent dispersal in a wild population of large herbivore” we look at this question on a roe deer population inhabiting a fragmented and anthropogenic landscape in South-West France.

Parasite abundance has been shown to have major consequences for host fitness components such as survival and reproduction. However, although natal dispersal is a key life history trait, whether an individual’s decision to disperse or not is influenced by the abundance of parasites it carries remains mostly unknown. Current and opposing hypotheses suggest that infected individuals should either be philopatric to avoid the energetic costs of dispersal (condition dependence) or disperse to escape from heavily parasitised habitats.

Our study site hilly and fragmented in the “coteaux de Gascogne” in South-West France.

 

Roe deer were capture during winter, we sample fresh faeces and we collared them with a GPS collared in order to follow their movement during approximately one year before to release them in site. Their natal dispersal behaviour could thus be evaluated with accuracy.

 

Collection of faeces sample during marking

 

Back to the field with a beautiful GPS collar

Our results show that dispersal propensity generally decreased with both increasing nematode abundance and with decreasing body mass. Within the dispersing segment of the population, individuals with high nematode abundance left their natal home range later in the season than less parasitised deer. These results clearly show that parasite abundance is an important component of condition-dependent dispersal in large herbivores. However, unexpectedly, three individuals that were both heavily parasitised and of low body mass dispersed. We suggest that this “leave it” response to high parasite levels in the natal habitat could represent a last ditch attempt to improve reproductive prospects, constituting a form of emergency life history strategy.

The authors through Lucie Debeffe who also took the photos

How life-history traits vary across longitude is studied in birds in the Amazonas in the Early View article “Variation in tropical bird survival across longitudes and guilds: a case study of the Amazone” by Jared D Wolfe and co-workers. Below is Jared’s summary of the paper:

Measuring the annual survival of birds, or the probability of a bird living from year-to-year, has fueled theory regarding life history strategy in temperate and tropical birds. For example, because tropical birds have fewer young over the course of a year relative to their northerly counterparts, scientists have often expected tropical birds to exhibit higher survival than temperate birds as part of a ‘trade-off’ in life-history strategy. In our paper we examined variation in annual survival among birds across the Amazon. We used a decade of bird capture data from the central Amazon to estimate the annual survival of 31 bird species and compared our results with those from western and eastern Amazonian forests.

We also examined differences in annual survival between bird species that differ in mass, foraging and nesting behavior at our study site in the central Amazon. In general, community-wide annual survival was remarkably similar across the Amazon, but several species did exhibit dramatic differences in survival estimates. The most striking variation in estimates of survival was exhibited by the White-plumed Antbird (Pithys albifrons), for which survival estimates were nearly twice as high in eastern than the western Amazon, but intermediate in the central Amazon. We also found that nest architecture moderately influenced annual survival of birds at our study site in the central Amazon. Our results suggest that geographic variation in survival may be significant for widespread Amazonian species.

How altered temperature might affect competition and herbivory in plant communities is studied in the early View paper “Concurrent biotic interactions influence plant performance at their altitudinal distribution margins” by Elina Kaarlejärvi and Johan Olsson. below is their summary of the paper:

The idea behind this paper was to test whether herbivory and competition influence growth and reproduction of lowland and tundra forbs at different altitudes. Previous studies had indicated that these biotic interactions could play a role in determining species altitudinal distributions, but this has been rarely experimentally tested.   We studied this in subarctic Abisko, in northern Sweden, on meadow habitats at two altitudes, at 600 and 900 m a.s.l. We selected five study sites at the two altitudes, each of them consisting of a pair of plots: one plot was fenced against large mammalian herbivores, while another was left open. Nested within this herbivore exclusion treatment we carried out biomass removal treatment to investigate effect of plant-plant interactions. We planted seedlings of lowland and tundra species to both altitudes and followed their growth and reproduction over two growing seasons.

Studying plant-plant interactions. Planting seedlings of lowland and tundra forbs to a subplot without neighboring vegetation at a low altitude site.

 

A fence against large mammalian herbivores in a study plot at a high altitude site. Early summer visit to the study sites to record signs of winter herbivory and check the condition of the fences.

We had expected to find competition at low altitudes and facilitation at high altitudes, but found that competition prevailed in both altitudes. However, high-altitude tundra forbs suffered more from competition; neighbor removal increased the proportion of flowering individuals and tended to increase growth of one of the high-altitude species more at low altitudes. Since the low altitude sites were about 2°C warmer (summer air temperatures) than high altitude sites, these results suggest that climate warming may strengthen competition and potentially shift lower distribution margins of high-altitude forbs upward. Interestingly, mammalian herbivores may counteract these climate-driven distribution shifts, as they reduced the growth of lowland forbs and enhanced the flowering of tundra forbs.

Lots of traits are climate dependent! In the Early View paper in Oikos “Genetically based latitudinal variation in Artemisia californica secondary chemistry” by Jessica Pratt and co-workers, terpenes are studied under different climatic situations.Below is a summary of the paper: 

Gradients in environmental conditions can serve as a ‘space for time’ substitution when trying to understand how species might respond to current and future environmental change and have thus become the focus of much recent work. Environmental gradients and gradients in biotic interactions often result in corresponding gradients in plant traits within a species. In our study, we examined variation in leaf terpene chemistry for the foundation species California Sagebrush (Artemisia californica) in Coastal Sage Scrub habitat across a 700 km latitudinal gradient in California. This gradient is characterized from south to north by a four-fold increase in precipitation.

Coastal Sage Scrub community in the Santa Monica Mountains with Californica Sagebrush in foreground

We collected California Sagebrush from five source populations distributed across this gradient and grew them in one common environment where we manipulated precipitation. Such common environment studies, when done in conjunction with environmental manipulations, provide a powerful approach to pinpoint the underlying causes of variation in plant traits and determine how such variation relates to large-scale ecological variation.

Coastal Sage Scrub community in the Santa Monica Mountains with Californica Sagebrush in foreground

Terpenes – one of the most diverse groups of plant secondary compounds – are important in providing defense against herbivores and also play several additional roles in the community. They are involved in plant-plant communication, drought and thermal tolerance, and adaptation to fire, and can influence plant relationships with other plants, animals, and microorganisms. We tested for genetically based variation in leaf terpene richness, diversity, concentration, and composition and examined whether precipitation was a key selective force on terpene chemistry.

California Sagebrush experimental garden plot

Our results showed that California Sagebrush source populations differed in terpene richness, diversity, concentration, and composition, with terpene composition and concentration varying clinally along the gradient. Plants from source populations that were closer together geographically had a more similar composition of terpenes than those farther apart, and terpene concentration decreased clinally from south to north. Our manipulation of precipitation suggests that selection for lower terpenes under increased precipitation may underlie this clinal pattern that we observed. Interestingly, we did not see a direct influence of the precipitation manipulation on terpene chemistry indicating these traits may not be phenotypically plastic in response to altered precipitation.

We conclude that changes in terpene chemistry under projected future climates will likely occur only through the relatively slow process of adaptation, and this will have important consequences for California Sagebrush’s interactions with the environment and a diverse community of associated species.

Have you ever tried to summarize your research in a poem? This haiku summarizes the Early View paper “Population-level consequences of risky dispersal”, by Allison K. Shaw and coworkers.

risky dispersal
whether too much, too little
both suboptimal

to selfishly leave
more or less than the others
may just hurt us all 

Oceans, they scare me
Nearby islands, too, stay far
I prefer it so.

Below, is a more traditional popular summary of the paper:

All living organisms move (disperse) at some point during their life. Many plants produce seeds that disperse away, and the offspring of most animals eventually grow up and move away from their parents. Moving has benefits as well as costs. By moving, an individual can find better food resources, or potential mates. However, by moving an individual also leaves behind familiar areas and faces the risk of possibly never finding a place to settle, or even dying along the way. So for each individual, there is some ‘best’ amount of movement: not too much and not too little.

However, moving individuals can also influence the population they live in: movement determines how spread out the population is across a habitat, and how much movement there is between different areas of the habitat. Therefore, from the perspective of the population, there is also a ‘best’ amount of dispersal. If individuals are spread out across the habitat, this can allow the population to reach a larger size, which increases the probability that the population will persist over time.

The question we ask in this paper is: what is the relationship between the amount of dispersal that is ‘best’ for an individual and the amount that is ‘best’ for the population? If they are not the same, which one is bigger and why?

To answer this question, we built a model (see Figure). We find that generally (1) when the area a population occupies is small, (2) where the habitat can only support a few individuals and (3) when there is a high risk of dying during dispersal, the amount of dispersal ‘best’ for an individual is smaller than the amount ‘best’ for the population. In these cases, the population size would increase if only individuals dispersed more. This suggests that as a conservation strategy for endangered species, restoring habitat may not be enough but may need to be combined with some form of assisted movement.

 

 

A schematic of our model. Individuals live in a habitat area of limited size, made up of smaller patches. If individuals disperse (leave the patch where they were born) they can either land successfully in another patch, die during dispersal, or die if they move beyond the habitat edge.

 

 

 

 

Apex predators are large carnivores that occupy the top trophic level of food webs. Globally, apex predators are assailed by disturbances such as persecution by humans. This is worrisome because changes in the density and distribution of apex predators can exert strong direct and indirect ecological effects that cascade through an entire ecosystem. However, our knowledge of these indirect ecological effects is still limited, particularly in marine environments. Coral reefs are one of the most diverse ecosystems, providing a useful model system for investigating the ecological role of apex predators and their indirect influence on lower trophic levels. In our work “Not worth the risk: apex predators suppress herbivory on coral reefs”, conducted on Lizard Island in the Great Barrier Reef (Fig. 1), we examined the indirect effects of two species of apex predators, a reef shark and large-bodied coral-grouper, on herbivore foraging we behaviour.

Figure 1. Location of study site

Using a novel approach of mimic predator models (Fig. 2) and GoPro video cameras we show that in the presence of an apex predator there is an almost localized cessation of algae consumption, due to the perceived risk of predation. Our work suggests that the indirect behavioural effects of apex predators on the foraging behaviour of herbivores may have flow-on effects on the functioning of coral reef ecosystems. This highlights that the ecological interactions and processes that contribute to ecosystem resilience may be more complex than previously understood.

 

Figure 2. Apex predator models. (a) Blacktip reef shark, (b) large coral-grouper and (c) small coral-grouper.

Picture below is of lead author Justin R. Rizzari (website: http://www.coralcoe.org.au/students/justin-rizzari)

 

The majority of pollination studies are performed in five countries, non of which in Africa. How does this bias affect application of the research in various geographic regions? Find out in the Forum paper in the April Issue of Oikos “Economic and ecological implications of geographic bias in pollinator ecology in the light of pollinator declines” by Ruth Archer and co-workers. Below is their summary of the paper:

Across much of the world pollinator loss has captured the attention of the media and the public.  In Europe pollinators regularly feature on the front page but here in southern Africa pollinator losses have received much less attention.  This doubtless reflects an underlying problem: in Africa, as across much of the world, we lack the data to record changing populations of pollinators or identify the threats facing them. 

In our opinion piece we aim to highlight that current understanding of pollinator losses (and more generally pollinator ecology) is based on data of comparatively narrow geographic scope.  More specifically, we show that almost half the data cited in thirteen recent meta-analyses, which ask important and diverse questions in pollination ecology, were collected in just five countries and Africa contributed only 4% of the data.  Does this matter?  Perhaps not, if the threats facing pollinators and responses to these challenges are similar across different regions, habitats and pollinator species.  However, this is unlikely.  There is enormous geographic variation in the distribution of anthropogenic disturbances, pests and parasites that are likely to impact negatively on pollinators.  For example, the Varroa mite, which is a major problem for European and North American honeybees, has less serious effects in subsaharan Africa and has not yet arrived in Australia.  Also, much more natural habitat remains in Africa than in Europe or America, although the speed of land use change is probably higher in Africa.  As pressures vary geographically, so too are different pollinators likely to vary in responses to them.  For example, subspecies of Apis mellifera differ in a suite of physiological and behavioural traits that make it unlikely that they will respond to ecological changes in the same way; therefore, management strategies designed around data collected on European honeybees may not be applicable to African subspecies.  Finally, from a socioeconomic perspective we need to better understand plant-pollinator interactions in understudied regions where the loss of pollination services could have immediate, dire effects: for example, where communities rely on subsistence farming or beekeeping for food security. 

If there are geographic gaps in our understanding of pollinator ecology and if these matter, what can we do about the issue given the socio-economic and logistical constraints that are likely responsible for much of this geographic bias?  In our article we offer solutions but, more importantly, hope to stimulate discussion on this important issue.  

Can hard-to-detect individuals of an endangered and declining population allow for testing of some of the major tenets of metapopulation theory while contributing to conservation efforts? A new multi-season occupancy model combined with observations on the Lower Keys marsh rabbit may have done just that. Read the Early View paper “Testing metapopulation concepts: effects of patch characteristics and neighborhood occupancy on the dynamics of an endangered lagomorph” by Mitchell J. Eaton and co-workers. below is their summary of the paper:

The Lower Keys marsh rabbit (LKMR, Sylvilagus palustris hefneri) is an endemic species found only on a handful of islands in the lower Florida Key islands. Following decades of decline caused by habitat fragmentation and degradation, sea-level rise and high rates of mortality inflicted by non-native predators, the LKMR was listed as endangered under the U.S. Endangered Species Act in 1990. Although several of these contributors to population decline have been improved, the distribution of the marsh rabbit continues to fall. With limited dispersal abilities, this secretive species persists in isolated habitat patches found within a highly fragmented landscape, challenging managers to identify viable solutions for their conservation and recovery. Given these conditions, a better understanding of the spatial aspects of marsh rabbit population dynamics could provide important insights and contribute to management efforts. We believed that a metapopulation framework would be the most useful for describing these dynamics. We were concerned, however, that existing metapopulation models were more theoretical than practical, based on too many assumptions and insufficient for dealing with the realities of a rare and hard-to-detect species. Therefore, we developed a new, flexible multi-season occupancy model that could test the concepts and assumptions of metapopulation theory, while investigating the dynamics of this species for the ultimate purpose of making recommendations for species management and recovery.

 Since its introduction in the 1960s, and following years of model development and application to natural systems, the theoretical underpinnings of metapopulation ecology have been strongly tied to assumptions about the relationship between neighboring patches, non-habitat (‘matrix’) characteristics and the probabilities of focal-patch extinction and colonization. Much recent work in metapopulation ecology has focused on developing advanced models that allow for incorporation of more detailed biological information to explain patterns in patch dynamics. Many of these models, however, have not taken into account the realities of imperfect detection in field sampling. As a result, only incomplete information on the abundance or occupancy levels of the surrounding landscape is available when making inference on the dynamics of a focal patch. As such, metapopulation models often rely on neighboring patch characteristics (e.g., perceived quality or size) as a proxy for the existence or abundance of colonizers and assume that local colonization will increase with patch connectivity. Local extinction probability has traditionally been modeled as a function of patch size, but is also predicted to be influenced by connectivity with neighboring habitat via a ‘rescue effect’. This latter process similarly depends on assumptions about the relationship between measurable patch characteristics and neighborhood occupancy, which can be difficult to quantify without consideration of the possibilities of non-detection.

 Building on recent advancements of the use of so-called ‘autologistic’ covariate models, we have developed a new multi-season occupancy model to explicitly incorporate estimates of neighborhood occupancy when modeling the dynamics of a metapopulation. Rather than treating the status or condition of a neighboring patch as certain (i.e., as a traditional, known covariate) we consider the occupancy of neighboring patches as an unobservable variable to be estimated. Our flexible model specification allows the ‘neighborhood’ to be defined in any number of ways, permitting nearly any a priori biological hypothesis to be tested. The model allows inclusion of a gradation of neighboring patch influence on the focal patch (e.g., habitat quality, distance, etc.) using patch-specific weights, as well as the quantification of non-habitat (e.g., water bodies) within the neighborhood. Using this modeling approach, we recast many of the assumptions of metapopulation theory as hypotheses to be tested explicitly.

 

Our results supported two of the major assumptions of metapopulation theory, namely that colonization probability is positively related to the occupancy of neighboring patches and that extinction probability is negatively related to local patch size. We also found support for the rescue effect, with extinction being mitigated by higher neighborhood occupancy, and for higher colonization rates being related to larger patch size. Model selection suggested that LKMR focal patch dynamics were influenced by a neighborhood effect size of approximately 1000m. Model results also suggest that patches in coastal areas (believed to be of higher quality for the species) experienced higher turnover rates than inland patches and that disturbance from sea-level rise, storm frequency and vegetation dynamics may be further destabilizing coastal patches. We found that lower-quality inland patches, which appear to be experiencing slower species turnover dynamics, may serve as refugia and provide an important source for colonization of coastal patches following local extinctions. Our findings can help managers better understand optimal spatial habitat configuration when planning restoration activities, predicted impacts of patch-specific removal of non-native predators and where translocations of LKMR would be most effective.

 

What are the roles of host phylogeny, transmission variables, and host traits in molding parasite metacommunity structure? Find out in the new Early View paper “Relative importance of host environment, transmission potential and host phylogeny to the structure of parasite metacommunities” by Ted Dallas and Steven J Presley. Here’s their own summary of the paper:

Identification of mechanisms that shape parasite community and metacommunity structures have important implications to host health,disease transmission,and the understanding of community assembly in general. In addition, a metacommunity approach can enhance the understanding of parasitological relationships among hosts, which may be reservoirs for emerging diseases or act as vectors that transmit diseases to humans or agriculturally important domestic animals.

 A metacommunity is typically defined as a set of ecological communities forming a network in space, such as  fish communities from a series of lakes across a landscape. However, Mihaljevic (2012) recently argued that metacommunity theory could be used to better understand parasite ecology. In our study, we considered host species to represent sites, with each host species harboring a distinct community of parasites. Each host species has a unique set of traits that define the environment for the parasites, the likelihood of parasite transmission to other host species, and the co-evolutionary relationships between hosts and their parasites.

 

 

 

Figure 1: Parasite distributions among rodent host species. Parasite group identity is indicated by color of the text in the graphic below the figure (e.g. Coccidians are in green).

 

We used data on rodent parasites from the Sevilleta Long Term Ecological Research Study to investigate parasite metacommunity structure from two perspectives. First, we used the Elements of Metacommunity Structure (EMS) framework to determine if parasite species distributions among hosts formed coherent structures (Leibold and Mikkelson 2002). Second, we assessed the relative roles of host phylogeny, host traits that can affect parasite transmission (e.g. home range size, diet breadth), and host traits that define the environment (e.g. body size, trophic status, longevity), using a variance partitioning analysis.

 Three distinct metacommunity structured occurred, Clementsian, quasi-Clementsian, and random. Despite the variation in structure,  host environment explained the largest proportion of the variation in community structure (~30%). This highlights the fact that no a priori relationship exists between particular structuring mechanisms and particular metacommunity structures. This suite of distinct responses from the same host metacommunity highlight the complex and diverse nature of host-parasite systems with respect to how parasites move through the environment, variation in life histories, and level of host specialization they exhibit. Mechanisms that contribute to parasite metacommunity structure may be highly complex, as host metacommunities can exhibit complex responses to local and spatial processes, with responses of hosts to large-scale environmental variation and responses of parasites to variation in host characteristics all contributing to parasite metacommunity dynamics.

 

Leibold, M. and Mikkelson, G. 2002. Coherence, species turnover, and boundary clumping: elements of meta-community structure. – Oikos 97: 237–250.

Mihaljevic, JR. Linking metacommunity theory and symbiont evolutionary ecology. Trends in Ecology & Evolution.

After more than 50 years of research into the ecology of large herbivores and predators in the greater Serengeti ecosystem, you might think that we know almost everything there is to know about this tropical savanna ecosystem. But in our article, “Episodic outbreaks of small mammals influence predator community dynamics in an East African savanna ecosystem” (Andrea E. Byrom et al.), we show that relatively little attention has focused on the role of small mammals (rodents and shrews) in tropical African savannas such as the Serengeti. This presents a critical gap in our understanding of one of Africa’s best known ecosystems.

Tropical savanna woodland, Serengeti National Park

We do know that in agricultural areas throughout East Africa, rodent populations fluctuate (outbreak) with large peaks in abundance, triggered by increased food availability during the dry season in response to the amount of rain in the preceding wet season. When outbreaks occur, species such as the multimammate rat Mastomys natalensis and the African grass rat Arvicanthis niloticus cause substantial economic damage in crop-growing areas. Before our study, however, little was known about the population dynamics of small mammals in tropical savanna, or their trophic importance, including as prey for some threatened carnivore species. Small mammals are a known food source for predators in this system, including mammalian carnivores in the weight range 1–18 kg, and birds of prey.

Arvicanthus niloticus, the African grass rat

It’s not surprising that researchers travel from all over the world to study an ecosystem as diverse and well-known as the Serengeti. Our team comprised researchers from Tanzania, New Zealand, Australia, the USA, Canada, and the UK – all scientists who had lived or worked in East Africa. Some of us have never met, but we all contributed to collection of the data that were used in this article. We pieced together a 42-year time series (1968-2010) on the abundance of 37 species of small mammals, derived from intermittent measures collected in Serengeti National Park and adjacent agricultural areas. Data on abundance of black-shouldered kites (1968–2010), eight other species of rodent-eating birds (1997–2010), and 10 mammalian carnivore species (1993–2010) were also collated.

Black-chested snake eagle, Circaetus pectoralis

We used climatic fluctuations and differences between unmodified and agricultural systems as perturbations to examine both bottom-up and top-down drivers of small mammal abundance: key to understanding responses to climate change and increasing human pressures adjacent to Serengeti National Park. Outbreaks occurred every 3–5 years in Serengeti National Park, with low or zero abundance of small mammals between peaks. There was a positive relationship between rainfall in the wet season and (a) small mammal abundance and (b) the probability of an outbreak, both of which increased with negative Southern Oscillation Index values. Rodent-eating birds and carnivores peaked 6–12 months after small mammals. In agricultural areas, abundance remained higher than in natural habitats.

 

The serval, Leptailurus serval

We conclude that small mammal outbreaks have strong cascading effects on predators in African savanna ecosystems. Changes in climate and land use may alter their future dynamics, with consequences for higher trophic levels, including threatened carnivores. Although outbreaks cause substantial damage to crops in agricultural areas, small mammals also play a vital role in maintaining some of the diversity and complexity found in African savanna ecosystems. Our study provides vital baseline data from which to monitor the future resilience of tropical savanna ecosystems.

 

The winner of the Global warming is – The long-tailed tit! Read more in the Early View paper “Climate change and annual survival in a temperate passerine: partitioning seasonal effects and predicting future patterns” by Philippa Gullet and colleagues. below is the press release, that at least have reached BBC News!

Climate change may be bad news for billions, but scientists at the University of Sheffield have discovered one unlikely winner – a tiny British bird, the long-tailed tit.

Like other small animals that live for only two or three years, these birds had until now been thought to die in large numbers during cold winters. New research published this week suggests that in recent years, weather during spring instead holds the key.

The findings come from a 20-year study of long-tailed tits run by Prof. Ben Hatchwell at the Department of Animal and Plant Sciences. The recent work is led by PhD student Philippa Gullett and Dr. Karl Evans from Sheffield, in collaboration with Rob Robinson from the British Trust for Ornithology.

“During spring, birds must work their socks off to raise their chicks,” said Philippa Gullett.

“For most small birds that live for only two or three years, not raising any chicks one year is a disaster. They might only get one more chance, so they can’t afford to fail.”

No surprise then that these birds are willing to invest everything and risk death if it means their young survive. The surprise is that weather makes all the difference. The research discovered that birds trying to breed in warm and dry springs have much better chances of surviving to the next year – a novel result that counters common assumptions about the cause of death for small birds.

“What seems to be going on is that the tits try to raise their chicks at any cost”, added Ms Gullett. “If it’s cold and wet in spring, that makes their job much tougher. Food is harder to find; eggs and chicks are at risk of getting cold. The result is that by the end of the breeding season, the adult birds are exhausted.”

The Sheffield team also found that despite no real effect of winter weather in recent years on adult survival, cold and wet autumns were associated with a higher death rate.

“We’re not saying that birds never die in winter – in harsh years there are bound to be some fatalities,” explains Dr. Karl Evans, supervising the research.

“However, it seems that in most years autumn weather plays a bigger role, perhaps acting as a filter that weeds out weaker birds before the real winter hits.”

Although autumns may get wetter in the coming years, any increase in mortality is likely to be offset by the benefits of warmer breeding seasons, when more benign

conditions reduce the costs of breeding.

Dr. Evans adds “Looking ahead to the future, our data suggest that every single plausible climate change scenario will lead to a further increase in long-tailed survival rates. While many species struggle to adjust to climate change, these delightful birds seem likely to be winners.”

The Rivelin Valley long-tailed tits featured in BBC’s Springwatch this year. To see the videos, go to:

http://www.bbc.co.uk/programmes/p01b7d6g – nest building behaviour

http://www.bbc.co.uk/programmes/p01bb1zf – chick provisioning and helping behaviour

What happens in the soil when forests are replaced by monocultures? Find out in the Early View paper “Habitat-specific positive and negative effects of soil biota on seedling growth in a fragmented tropical montane landscape” by Camila Pizano and co-workers. Below is the author’s summary of the study:

In this study we showed evidence that when montane tropical forests are replaced by monocultures of coffee and pasture grasses, plant-soil interactions change. Plant-soil interactions have been found to mediate the coexistence between plant species, and maintain biodiversity across a wide array of habitat types. However, we still have a poor understanding on how these interactions vary across neighboring habitat types dominated by different plant species. Furthermore, there are few studies on plant-soil interactions that have been done in both the greenhouse and the field.n this study we showed evidence from the greenhouse and the field that when montane tropical forests are replaced by monocultures of coffee and pasture grasses, plant-soil interactions change. Pastures accumulate soil organisms that are detrimental to pasture grasses and slow growing shade-tolerant tree species but are beneficial for fast growing, pioneer forest tree species. Forests accumulate soil organisms detrimental for pioneer species, but beneficial for slow growing, shade-tolerant forest tree species. And coffee plantations contain soil organisms that enhace the growth of pasture grass and pioneer forest tree species, but decrease the growth of shade-tolerant forest trees. These results suggest that the soil biota present in agricultural lands benefits primary sucession of montane tropical forests, but hinder the establishment of late sucessional forest species. Soil organisms in pastures also hinder the growth of pasture species that are important for cattle production.

How accurate are different forecast models for predicting population dynamics? That, and how predictable various animals actually are, was tested in the study “Complexity is costly: a meta-analysis of parametric and non-parametric methods for short-term population forecasting”,  by Eric J. Ward and colleagues, that is now published online in Oikos. Below is the author’s summary of the study:

Forecasting ecological data presents a unique set of challenges compared to other types of time series data (stock prices, weather) – two of the most common sources of uncertainty arise from (1) scientists not measuring populations perfectly, and (2) mechanisms responsible for population fluctuations are generally complex and not measureable at a population-wide scale (e.g. density dependence). Many ecological and fisheries models are made complex in an attempt to capture biological realism. Recent work on simulated and real datasets (Perretti et al. 2013 PNAS; Sugihara et al. 2012 Science) has shown that more accurate predictions can be made from simpler non-mechanistic models. Our paper presents the results of a forecasting competition, comparing a wide range of time series models to ~ 2400 time series, representing a range of vertebrate taxa. We found that in general, the best 1-5 year forecasts originated from simple models, such as a random walk (where the predicted population size is the current population size). Taxa that have strongly cyclic population dynamics, such as sockeye salmon, are the easiest to forecast, and warrant the use of more complex types of non-mechanistic models. Across all marine fish species, we found that longer lived species, or those with larger body size are easier to predict (presumably because they have smaller recruitment variability). Similarly, for birds, we found that higher trophic levels were also correlated with better predictions.

All of the time series included in our analysis were relatively long in ecology (25 continuous data points). The failure of many of the methods we considered suggests that improvement in forecasting ability is unlikley to come from better non-mechanistic forecasting methods or more annual population data; instead we recommend that efforts be made to better understand environmental drivers, which can be included as covariates.

Thanks to giant water bugs’ ferocious feeding habits and their extreme natural environment, authors Kate S. Boersma and colleagues, now have a greater understanding of how biological communities may respond to predator extinctions under increasing global environmental variability. All after having performed the study “Top predator removals have consistent effects on large species despite high environmental variability” published Early View in Oikos. below is their summary of the study and a presentation of the giant water bug.

We used the giant water bug system to explore the consistency of top predator effects in ecological communities that experience high local environmental variability. We experimentally removed giant water bugs from arid-land stream pool mesocosms in southeastern Arizona, USA, and measured natural background environmental conditions. We inoculated mesocosms with aquatic invertebrates from local streams, removed giant water bugs from half of the mesocosms as a treatment, and measured community divergence at the end of the summer dry season. We repeated the experiment in two consecutive years, which represented two very different biotic and abiotic environments. We found that giant water bug removal consistently affected large-bodied species in both years, increasing the abundance of mesopredators and decreasing the abundance of detritivores, even though the identity of these species varied between years. Our findings highlight the vulnerability of large taxa to top predator extirpations and suggest that the consistency of observed ecological patterns may be as important as their magnitude.

Giant water bug (Abedus herberti) consuming a dragonfly nymph (Oplonaeschna).

At ~3cm in length, giant water bugs (Abedus herberti) may appear unlikely top predators. Yet these aquatic invertebrates dominate the food webs of many small headwater streams in the arid southwestern United States. Giant water bugs use raptorial forelimbs to immobilize prey and piercing mouthparts to inject digestive enzymes and consume the liquefied tissue, allowing them to consume large vertebrate and invertebrate prey. These insects are flightless and thus highly vulnerable to changing hydrology caused by increasing droughts and anthropogenic water withdrawals in arid regions. Streams containing giant water bugs are characterized by seasonal flood/drought cycles and high natural environmental variability, making this an ideal study system to address fundamental questions about the relationship between predator loss and an increasingly variable abiotic environment.

“Which fruit should I eat?” – a decision both migratory and resident birds have to make over and over each autumn. This decision – and the consequences of it is studied in the Early View paper “Consistency and reciprocity of indirect interactions between tree species mediated by frugivorous birds” by Daniel Martinez and co-workers. Below is the authors’ summary of the paper:

Do fruiting plants compete or facilitate each other for frugivores providing seed dispersal? This question has been previously answered through single-species, short-term studies, that have evidenced indirect interactions between plants. Nevertheless this leaves unanswered another important question. How variable through time and across species within a community are these interactions? Resolving this question will help us to reveal the actual relevance of these interactions in natural systems.

Our study was developed in a straightforward plant-frugivore system. Three species of fleshy-fruited trees (hawthorn Crataegus monogyna, holly Ilex aquifolium and yew Taxus baccata) coexist in the secondary forest of the Cantabrian mountain range (NW Spain). Their seeds are mainly dispersed by a common assemblage of frugivorous blackbirds and thrushes (Turdus spp.). During autumn and winter both resident and wintering birds have to choose where to feed, among the fruiting trees belonging to the three plant species. Decisions are taken not only considering a given individual tree, but also the trees standing in its neighborhood, with the aim of optimizing in which to perch.

Far from general patterns of competition and/or facilitation between these tree species, we find that, like often in nature, variability seems to be the rule. The arising of indirect interactions and their sign shifted between species and across years.  Plant-frugivore systems, even those simple like this, are functionally complex. The abundance and spatial distribution of fruits changed from year to year. While some tree species increased their crops other became scarce. Birds faced very different fruiting scenarios every autumn and, thus, the costs and profits of feeding on different trees changed from year to year.

We do not attempt to explain the rules driving indirect interactions within a community, but to show their complexity, consistency between years and reciprocity between species. Taking this variability into account is crucial to understand the role of indirect interactions in the structuring of natural communities.

Artwork and photo credits: Daniel Martínez.

Ecosystem engineering, the physical modification of the environment by organisms, may well be the most common kind of non-trophic interaction – nearly as ubiquitous as eating and being eaten, and often as influential. Because species are affected by the physical environment, and because all ecosystem engineers belong to food webs while also modifying the environment, their dual role is potentially one of the most important bridges between the trophic and non-trophic. For example, many ant species are predators and important earth movers (see picture). Nevertheless, research in both areas has remained largely independent.

An upcoming paper (“Integrating ecosystem engineering and food webs” by D. Sanders, C.  Jones, E. Thébault, T. Bouma, T. van der Heide, J. van Belzen, and S. Barot) explores how to integrate ecosystem engineering and food webs. The paper provides rationales justifying integration, and then a framework for understanding how engineering can affect food webs and vice-versa, and how feedbacks alter dynamics. A simple food chain model is then used to illustrate the dynamics in the presence and absence of extrinsic environmental perturbations. The paper argues that current understanding of how engineering shapes food webs and vice versa is perhaps more hampered by lack of knowledge about food web responses to abiotic change than knowledge about how ecosystem engineers can cause such change; and that this is compounded by the fact that engineering and food web studies are rarely studied together in the same system. The authors argue that with appropriate studies and integrative models, conjunction is achievable, helping pave the way to a more general understanding of interaction webs in nature.

Ecosystem engineering and predation by Formica ants (photo credit Dirk Sanders)

What will happen at the meta-community level with all exposure to human activities in various ecosystems? To answer this, Anne Teyssèdre and Alexandre Robert have simulated a few alternative, presented in the Early View study “Contrasting effects of habitat reduction, conversion and alteration on neutral and non neutral biological communities”

Below is the author’s summary of the paper:

How can we explain the local coexistence of numerous ecologically similar species in the same trophic level communities (like plant, perching bird, or rodent communities), and how will these communities react to the current massive global habitat changes driven by human activities?

While these two questions are necessarily linked, scientists’ current answers seem contradictory. On one hand, Hubbell’s (2001) neutral theory of biogeography and biodiversity (NTB) succeeds to explain – and even predict – many community patterns observed and measured by biologists and biogeographers for several decades, among which the well-known “Arrhenius law”, or power law species-area relationship (SAR). [First proposed by Arrhenius in 1921, this empiric ‘law’ relates the richness at equilibrium (S) of a same trophic level community, in number of species, to the area (A) it occupies, in a power relationship: S = c.A^z]

Hubbell’s NTB assumes that the small ecological differences among the species composing a community can be neglected confronted to the large stochasticity (i.e. randomness) of local colonization, reproduction, extirpation and speciation events. It assumes the ecological and demographic equivalence of all species in the community at a local scale, in other terms. But this assumption clearly contradicts many biological and evolutionary data, among which the mere fact of evolution by natural selection. [Hubbel’s neutral model must hence be considered as a useful null hypothesis to confront other community dynamics models, and to explore the correlates of “ecological drift”, like Kimura’ s neutral theory of genetic evolution may be used to explore the correlates of genetic drift.]

To tackle this intriguing issue, we modeled the dynamics of different species communities confronted to different types of habitat changes. More explicitly, we defined a small number of species categories differing in their level of specialization to different habitat types and explored the impact of different simulated habitat changes on a regional community mixing generalist and specialist species (specialization model), compared to that of a community composed of ecologically equivalent species (neutral model), combining stochastic, deterministic and selective processes.

We noteworthy found that (i) both models ruled with habitat reduction predict an approximately power law SAR, in conformity with empirical observations; (ii) with the specialization model, but not with the neutral one, habitat conversion (i.e. land use change) and alteration (e.g. aridification, acidification, eutrophization…) may increase regional species richness until a threshold; (iii) habitat alteration, with the specialization model, leads to the rarefaction of specialist species and the expansion of generalist species, i.e. to the functional homogenization of the community at local and regional scale.

While not predicted by the NTB, these two later patterns are currently observed in many local or regional communities confronted to habitat changes.  We conclude that this kind of model mixing a few stochastic, deterministic and selective processes may be use to explore and anticipate the dynamics and biodiversity patterns of living communities at different geographic scales, in response to different environmental strategies and scenarios.

Now on Early View: A study about functional traits in Sphagnum and how it affects carbon cycling. “Tradeoffs and scaling of functional traits in Sphagnum as drivers of carbon cycling in peatlands” by C.G. Laing and co-workers. Below is the author’s own summary of the study:

The effect of temperature on the decomposition of vegetation has been extensively studied within the climate debate. However, the functional traits of vascular plants have been shown to strongly effect decomposability independently of temperature.

Our study  in Oikos explored whether functional traits could explain decomposition of the peat-forming moss Sphagnum since its growth plays a substantial role in global carbon storage.  We coupled classical approaches with the first allometric scaling calculations for Sphagnum to identify water and light availability as controls on growth strategy that impact decomposition rates. It is our hope that our fellow researchers will test the scaling relationships developed here further.

Image: Sample collection 07-09-2010 on Ryggmossen Bog, Sweden

If many mouths eat a lot of a not so preferable foot item – i.e. large numbers of city rats happen to live underground where they only have access to garbage-like food items – this does not tell us that another foot item not accessible to the crowd is genuinely much more preferable – which rat would refuse to snack on gourmet cheese if there wouldn’t be obstacles that allow only brave foragers to have a bite on it?

In ecological network studies, species preferences are often summarized as to how often species interact with each other for multiple species.  This can be foragers feeding on different resources, for example.

While indices and summary statistics for explaining resulting network structure have experienced much sophistication in recent years, the fact that interaction frequencies are the product of preferences / attraction towards interacting partners and availability / abundance of interacting species has received little attention.

The early view paper “Population fluctuations affect inference in ecological networks of multi-species interactions” by Konstans Wells and co-workers, shows that population fluctuations have considerable impact on calculated network statistics. So an increasingly large range of values can be inferred from the same ecological system the more populations fluctuate.  Considering  abundance fluctuations and sampling effort in ecological networks may not only improve inference, but also open promising perspectives to novel questions in ecological research  – certainly if the crowd makes it to the most preferable piece of meal, this will affect all aspects from individual behaviour to what is left on the plate for the next round of interactions, be it for single species or communities.

How different kinds of ecological aspects affect the future of invasive plants is studied in the Early View paper:“Neighborhood-contingent indirect interactions between native and exotic plants: multiple shared pollinators mediate reproductive success during invasions” by Susan Waters and co-workers. Below is the author’s summary of the study:

In the highly fragmented prairies of western Washington’s Puget Trough, conservation focuses on managing invasive plant species that may directly compete with rare native forbs.  However, the area also has a depauperate pollinator community, and the highly overlapping assemblage of generalist pollinators visiting native and exotic dandelion-like forbs suggested to us that native and exotic plants might also interact indirectly through pollinators (for example, by competing for pollinator visits, or by altering the amount of conspecific pollen transferred to a neighbor). 

Given that one of the dominant invaders, Hypochaeris radicata, has a patchy distribution, and that pollinators often alter their foraging patterns in response to floral density, we speculated that pollinator-mediated indirect interactions might play out differently in H. radicata-dominated floral neighborhoods than in less-invaded, more diverse floral neighborhoods. 

However, further observation soon caused us to suspect that the story was more complex. There were multiple pollinator intermediaries between the plants, and we realized that pollinator groups might differ in their responses to different floral neighborhoods. We hypothesized that there were at least two ways that floral neighborhoods might alter pollinator behavior: either by changing whether pollinators chose to forage in the patch at all, or by changing the foraging decisions pollinators made once they arrived in the patch.

We compared pollinator visitation and seed set by two native forbs and H. radicata in three floral neighborhoods: high density native (and low density H. radicata), high density H. radicata (and low density native) and low density of both H. radicata and natives. Eusocial bees, solitary bees, and syrphid flies all visited the H. radicata and the two native forbs we observed, but the proportion of total visitation to a plant species from each pollinator group depended on the floral neighborhood.  Accordingly, dense exotic H. radicata neighborhoods facilitated seed set in one native forb, Eriophyllum lanatum, while diminishing seed set in another native forb, Microseris laciniata.  Context-dependent pollinator visitation, mediated by multiple pollinators, thus resulted in opposing effects of an exotic plant on two native species.

We’re very happy to welcome Dr Martijn Bezemer, NIOO-KNAW, the Netherlands to our editorial board.

Martijn, what’s your main research focus at the moment?
My main research focus is on aboveground-belowground interactions. I study how (i) soil biota (ii) manipulations of the soil community, and (iii) soil mediated effects of neighbouring plants affect the nutritional quality of focal plants and the aboveground plant-insect interactions on those focal plants. Further, I study the role of soil organisms in restoration of grasslands on former arable land. Much of this work is carried out in the field.

Can you describe you research career?

My MSc was in Crop Protection in Wageningen, The Netherlands. I started my carreer at Imperial College at Silwood park, where I studied the effects of elevated CO2 and elevated temperature on plants, insects and parasitoids in model ecosystems in the ecotron controlled environment facility. This was from 1995 to 1999. From 1999 to 2000 I went to UC Berkeley for a post-doc. Here I studied biological control of codling moth in walnut orchards using introduced parasitoids. In nov 2000 I moved back to the Netherlands for a post doc at the Netherlands Institute of Ecology (NIOO). I first studied the effects of root herbivory by wireworms on aboveground plant-insect interactions in cotton and then worked on the effects of aboveground and belowground multitrophic interactions on plant diversity and succession. In 2004 I moved to Wageningen University but continued working on linking aboveground and belowground diversity. In 2008 I am moved back to the NIOO, and I have a position as senior scientist.

How come that you became a scientist in ecology?

During my MSc I focused agronomy. My stay at Silwood Park made me an ecologist.

What do you do when you’re not working?

I like to play guitar, read literature and DIY type activities in our house

For the February and March issue we have selected three articles as Editor’s choices that are currently open access. We selected papers that are at the heart of our publication mission, so papers that aim at providing synthesis in ecology. The work by Sergio Estay and colleagues focusses on the role of temperature variability for insect performance, and how these individual changes in performance feedback on population dynamics. The work is theory-based and provides a framework to organize research of the role that thermal mean and variability plays in individual performance, and how it may affect population dynamics. By developing null models, they demonstrate that potential changes in the intrinsic population growth rate depend on the interaction of mean temperature and thermal variability, and that the net effect of the interaction could be synergistic or antagonistic. The theoretical models are evaluated using data compiled from literature.

A promising avenue to test these theoretical predictions is using experimental microcosms. While it remains questionable to which degree such small-scale studies scale up to macroscopic patterns, they allow a tight coupling between simple models and real data that are collected in a standardized manner. Clements and colleagues followed this approach to test the effects of directional environmental change on extinction dynamics in experimental microbial communities as predicted by a simple model. Based on the assumption that temperature does alter an individual’s metabolic rate, and consequently birth and death rates, they predict that in declining populations, these alterations may manifest as changes in the rate of that population’s decline, and subsequently the timing of extinction events. Clements and colleagues find that extinction occurs earlier in environments that warm faster, and importantly that phenomenon can be accurately predicted by a simple metabolic model. Increasing the number of parameters that were temperature-dependent increased the model’s accuracy, as did scaling these temperature-dependent parameters.

 

The last Editor’s choice for now is the Per Brinck contribution from 2013 by Sharon Strauss: Ecological and evolutionary responses in complex communities: implications for invasions and eco-evolutionary feedbacks. In this contribution, Strauss discusses our current understanding on how interactions between ecological and evolutionary dynamics affect the organization and functioning of simple and more complex communities. Based on her own work and that of many others, she examines how community complexity may influence the nature and magnitude of these eco-evolutionary feedbacks, and how an escape from community complexity per se affects the success of invaders. She synthesizes the diverse dynamics into three general types: those generating alternative stable states, cyclic dynamics, and those maintaining ecological stasis and stability.

 

How does grazing affect the soil? Find out in the Early View paper “Grazing-induced changes in plant–soil feedback alter plant biomass allocation” by Ciska van Veen and co-workers.

Cows and rabbits, feed on plants. With that they change plant growth directly, for example by removing leaves. In addition they may change an array of soil conditions, such as the amount of nutrients or root feeders in the soil. In this study we found that these changes in the soil from grazed grasslands influenced plant growth (photo 1).

Photo 1: greenhouse experiment where the researchers investigate the growth of different plant species in soils from grazed and ungrazed grasslands.

However, the impact of cows and rabbits on plant growth via changes in the soil, did not help us to understand the species composition of plants in the field (photo 2). Thus, the direct influence of cows and rabbits on plant growth seems more important for plants in the field.

Photo 2: field experiment in the Junner Koeland Nature Reserve (the Netherlands). Cows and rabbits are excluded with fences from parts of the nature reserve. The researchers used the soil from inside and outside the fences to test the response of plant species. In addition, the researchers monitored the plant species composition inside and outside the fences to test if the response of the plants to the different soils could help to understand the plant species composition.

Recently, Wiley released the list over most downloaded Oikos papers during 2013. Many of the papers are familiar titles, that were published a few years ago. However, two of the papers published during 2013 actually managed to climb the ladder and take place among the top ten. Both of them were presented at this blog. Both of them were selected as Editor’s choice.

Here’s a link to the top 10 list:

http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1600-0706/homepage/MostAccessed.html

The two 2013 papers have been opened for Free Download by Wiley for the next two weeks, so take your chance to download them today! And the papers are:

Is the Oikos chief editor the only one working? Dries is busy handling manuscripts while James and Maria dream of seeds and eagle owls, respectively!

Dispersal and species’ responses to climate change with 1384 downloads

by J. Travis et al.

Link to paper: http://onlinelibrary.wiley.com/doi/10.1111/j.1600-0706.2013.00399.x/full

Link to blogpost: https://oikosjournal.wordpress.com/2013/09/13/dispersal-at-the-heart-of-our-thinking/

and

The elephant in the room: the role of failed invasions in understanding invasion biology with 1604 downloads

by Zenni and Nunez

Link to paper: http://onlinelibrary.wiley.com/doi/10.1111/j.1600-0706.2012.00254.x/full

Link to blogpost: https://oikosjournal.wordpress.com/2013/02/01/the-elephant-in-the-room/

A hybridization event at the bottom of the food chain may affect organisms several steps up the chain. Read more in the early View paper: “Bottom–up regulates top–down: the effects of hybridization of grass endophytes on an aphid herbivore and its generalist predator” by Susanna Saari et al. 

Below is their popular summary of the study:

Hybridization is a well understood process where organisms fuse to form new organisms with unique characteristics. However, the ecological consequences of hybridization in the microbial partners of plants are largely unknown. We studied the effects of hybridization of microbial plant symbionts on the feeding preference and performance of herbivores and their natural enemies. In our laboratory experiments, we used the grass Arizona fescue as the host plant, Neotyphodium endophyte as the microbial plant symbiont, the bird cherry-oat aphid as the herbivore and the pink spotted ladybird beetle as the predator. Neither endophyte infection (infected or not infected) nor hybrid status (hybrid or non-hybrid) of the endophyte affected aphid reproduction, aphid host plant preference or body mass of the ladybirds. However, development of ladybird larvae was delayed when fed with aphids grown on hybrid endophyte infected fescue compared to ladybird larvae fed with aphids reared on either non-hybrid infected fescue, non-hybrid, endophyte-removed fescue and hybrid, endophyte-removed fescue.

A pink spotted ladybird and bird cherry-oat aphids on Arizona fescue. In our experiment, pink spotted ladybirds avoided aphids that had been feeding on grasses infected with hybrid Neotyphodium endophytes.

Furthermore, adult ladybrids were more likely to choose all other types of fescues harboring aphids rather than hybrid endophyte infected fescues. Our results suggest that the hybridization of microbial symbionts may negatively affect predators such as the pink spotted ladybird and protect herbivores like the bird cherry-oat aphids from predation even though the direct effects on herbivores are not evident.

Neotyphodium endophyte (red lines) growing between the cells (the red circles) of a plant. Endophytes are micro-organisms growing within the tissues of plants without causing any symptoms for the host. Some fungal endophytes can fuse with other fungi growing within the tissues of the host plant thereby forming a hybrid fungus with unique characteristics.

Ecological synthesis is tricky. One of its many challenges is that empirical data rarely paint a clear picture either supporting or refuting a given hypothesis. More typically, empirical studies have diverging results. But even for hypotheses where refuting evidence is overwhelming, ecologists are often reluctant to abandon them (see Oikos Blog on Zombie Ideas).

In our paper “The enemy release hypothesis as a hierarchy of hypotheses” (Heger & Jeschke in Oikos, early view), we explore a novel method for assessing ecological hypotheses based on empirical evidence: the Hierarchy-of-Hypotheses (HoH) approach. This approach was born during a joint project (see Jeschke et al. 2012 in Neobiota) and a workshop titled ‘‘Tackling the emerging crisis of invasion biology: How can ecological theory, experiments, and field studies be combined to achieve major progress?’’ (see Heger et al. 2013 in Ambio). When we discussed the problem of imprecise formulations of hypotheses in invasion ecology (another challenge to ecological synthesis), it became obvious that we need a framework for integrating both broad and narrow hypotheses. Our suggestion for such a framework is the HoH approach, where a broad, overarching hypothesis branches into increasingly narrow and specific formulations of this hypothesis (i.e. sub-hypotheses). The most specific formulations are empirically testable.

The HoH approach can serve as an organizational tool (e.g. to structure research questions, or to organize conceptual work), but also for assessing hypotheses. In our paper, we show the first worked-out example for a HoH. We used the method for a well-known and much discussed hypothesis of invasion ecology: the enemy release hypothesis. Applying a newly developed weighting procedure, we assessed empirical evidence for each sub-hypothesis. Our results show that overall, there is nearly as much evidence in favor as against the enemy release hypothesis; hence, the overall picture is quite blurry. However, a closer look at the sub-hypotheses reveals that specific formulations of the enemy release hypothesis are clearly empirically supported, whereas other formulations receive hardly any support (see Fig. 1). This example shows how powerful the HoH approach can be to make a blurry picture clear.

 

Figure 1. Schematic illustration of a hierarchy of hypotheses (HoH) for the enemy release hypothesis. The scheme classifies empirical tests of the enemy release hypothesis according to three criteria, shown as three hierarchical levels: (1) indicator for enemy release; (2) type of comparison; and (3) type of enemies. The combination of these criteria results in different sub-hypotheses which are drawn as boxes; the number of empirical tests available for each sub-hypothesis is given in the respective box (‘n’). The boxes are color-coded as follows: red boxes: 50% or more of the data question the sub-hypothesis, and n≥5; green boxes: 50% or more of the data support the sub-hypothesis, and n≥5; white boxes: all other cases (i.e. n<5 or inconclusive data).

In writing the paper, we had several discussions on how much empirical support is needed to call a hypothesis ‘supported’. For Fig. 1, we agreed on the threshold of 50% support, but this is debatable. We believe that ecology needs a discussion on these questions: How do we decide whether a hypothesis is worth keeping? How much supporting evidence is needed, and how much refuting evidence can be tolerated? We very much hope that our paper stimulates discussions on these and similar questions. Also, it would be great to see more HoHs being created, in ecology and beyond.

Tina Heger & Jonathan M. Jeschke

Last week, the annual Oikos meeting was held in Stockholm. This year as a Nordic event, with speakers from both Sweden, Norway, Denmark, Finland and Iceland.

The big happening was of course, that Prof. Bob Holt was awarded the Per Brink award.

Bob gave a fantastic talk, managing to turn theoretical ecology to an exciting fairytale!

After the talk, Oikos’ Editor in Chief, Dries Bonte and Managing Editor, Åsa Langefors (on the photo) handed over the diploma and the glass apple.

The diploma is a wonderful piece of artwork, painted by biologist and artist Linnea Fredriksson http://linnea.linneaartline.com Linnea reads most of the awardee’s scientific work and uses the study species and focus to create the picture.

Take a closer look at Bob’s diploma:

Congratulations Bob! http://people.biology.ufl.edu/rdholt/

Why might you find scientists out on a pitch black night on a remote Alaskan lake driving two 18’ boats with a net towed in between?  Fun, tradition, data collection?   Well, all of the above, assuming the weather is nice.  In our article, “Climate variation is filtered differently among lakes to influence growth of juvenile sockeye salmon in an Alaskan watershed,” we rely on generations of scientists doing just this to evaluate how juvenile salmon growth responds to climate variability.

Long-term datasets provide opportunities to disentangled pattern from noise.  Establishing and maintaining long-term datasets requires marshalling the human, financial, and logistical support necessary to return year after year to collect data.  The University of Washington’s Alaska Salmon Program (http://fish.washington.edu/research/alaska/ or https://www.facebook.com/AlaskaSalmonProgramFRI) has been sending scientists to remote southwest Alaska since the mid-1940s to collect data on juvenile sockeye salmon and their habitats.

Our field methods today are remarkably similar to those established over 60 years ago.  Every summer at the end of August, we head out onto our study lakes (in this case, Chignik and Black lakes) on small boats just as the sun is heading down.  Armed with a net that looks a like a gigantic windsock with arms, flashlights, a GPS, and trays and buckets, we get ready to capture and measure juvenile sockeye salmon.  Juvenile sockeye salmon feed near the surface at night making them more easily sampled by our nets.  We tow the net between our “master” and “slave” boats according predetermined tracks, hoping to steer far clear of shore.  After towing for a set time, we haul in the net and inspect our catch.  Fish we catch are subsampled and brought back to our field station to be measured and weighed.

By sampling year after year, we can observe the variation in juvenile sockeye salmon growth during their first summer of life and evaluate causes of variation in growth.  Growth is an important determent of their ability to avoid predators as well as survive winter conditions and ocean migration.  In our study we investigated if the year to year variability in growth was explained by climate variation, including differences among years in winter and spring air temperature.  Using additional information regarding juvenile salmon growth collected from adult sockeye scales, we were also able to investigate whether the same regional climate such as air temperature elicits the same growth response from juvenile salmon in different lake types.

We found that the average size of juvenile salmon has been increasing over time.  However, the same changes in air temperatures did not always lead to the same response in juvenile salmon growth in different lake types.  Juvenile sockeye salmon grew larger in years with warmer spring and fall temperatures in deep, cold Chignik Lake.  Just upstream in shallow, warm Black Lake, juvenile salmon grew less in years with warmer air temperatures.  These differences in growth indicate that landscape diversity within watersheds filters climate such that organisms experience and respond differently among habitats. Our ability to manage for resilient ecosystems in the face of ongoing environmental change may be improved by considering within, as well as among, watershed climate filtering.

Having one predator chasing you is scary enough, but what about having two? Hunting in different habitats? Lucky me not being  roe-deer! Read more in the Oikos Early View paper “Living and dying in a multi-predator landscape of fear: roe deer are squeezed by contrasting pattern of predation risk imposed by lynx and humans” by Karen Lone and colleagues. Below is Karen’s summary of the paper:

The challenge of managing large carnivores in a multiple-use landscape in Norway has motivated a large research effort to understand carnivore ecology and their impact on livestock and other wildlife, in addition to extensive monitoring. I was lucky to be able to use some of the data collected in this larger framework to investigate predator-prey interactions and the landscapes of risk for roe deer. Our goal was to look at the effect of multiple predators preying on a single prey species. Roe deer have a natural predator in lynx, and a functional predator in hunters. We investigated how predation risk from these two predators related with habitat characteristics by comparing kill sites to sites used by live roe deer, and anticipated that they produced conflicting landscapes of risk.

LiDAR data from one field plot with radius ca 28m in a 3D perspective – points are colored by height above the ground, so vegetation hits stand out in warmer colors than ground hits.

In this paper we try to use Light Detection and Ranging (LiDAR) data to predict risk. We had access to a LiDAR dataset obtained by airborne laser scanning the entire 900km² study area. As well as giving spatially extensive information, it also gives a lot of detail: the point cloud of height measurements (points at which laser beam was reflected) gives a nice visual impression of vegetation structure (see figure). Especially important LiDAR variables in our analysis of risk were laser echoes from the 0.5-2m height segment, corresponding to the density of the understory vegetation. The final predictive maps of predation risk are based on LiDAR data, a terrain model and a map of roads.

Our study site Hallingdalen, a valley in central Norway, is a multiple-use landscape.

Both LiDAR data and field data provided the same findings – that predation risk from lynx was higher in denser habitat, and increasing with distance from roads. Conversely, the risk of being killed by a hunter was higher in more open habitat and closer to roads, indicating that roe deer face a trade-off between the two predators along these gradients. With regards to some habitat characteristics, the risk gradient aligned for lynx and hunter – both inferred greater risk in more rugged terrain. From the spatial predictions, we found that only 1% of the area had low predation risk from both predators. In other words, when we considered two predators together rather than each on their own, the roe deer had almost no refuges where they can escape predation altogether. Our study raises questions of how roe deer adapt their behavior, if at all, to reconcile the risk landscapes they face, and whether the temporal variations between their two predators may be the key to avoiding mortality.

The first editor’schoice for 2014 is the work of Alexander Kubisch and colleagues. This invited contribution synthesizes how feedbacks between ecological and evolutionary on dispersal shape species ranges and range dynamics. The manuscript is a systematic review on the existing literature and prevailing insights combined with novel modeling approaches to demonstrate the relevance of evolutionary forces at all hierarchical levels of biological organization (from landscapes to communities via populations, individuals and genes) that affect distribution ranges. Since Oikos has been publishing many relevant key-papers in this field, the authors have additionally compiled a virtual issue which will be available in January and which is introduced here. Alexander Kubisch won the Horst-Wiehe-prize at the GfÖ annual meeting for this synthesizing range biology work.

Synthesis: What factors are responsible for the dynamics of species’ ranges? Answering this question has never been more important than today, in the light of rapid environmental changes. Surprisingly, the ecological and evolutionary dynamics of dispersal – which represent the driving forces behind range formation – have rarely been considered in this context. We here present a framework that closes this gap. Dispersal evolution may be responsible for highly complex and non-trivial range dynamics. In order to understand these, and possibly provide projections of future range positions, it is crucial to take the ecological and evolutionary dynamics of dispersal into account.

The second editor’s choice for January is the research paper by Qi and colleagues. They analysed a large trait database involving 1355 species from the northeastern verge of the Tibetan Plateau to test to which degree seed mass is affected by changing abiotic conditions along altitudinal gradients. The analysis of such a large dataset revealed the relevance of two opposing forces, stress tolerance and energy constraints. Subsequently, life history cycles, resource allocation strategies and dispersal agents appeared to be more important drivers in seed mass than pollination efficiency along a pronounced latitudinal gradient. Clearly, only an integrated analysis of the potential drivers of a single trait like seed size may lead to such comprehensive insights.

Synthesis: With increasing elevation, seed mass may be either larger for its advantage during seedling establishment (‘stress-tolerance’ force), or smaller owing to energy constraints. Our paper shows some novel and importance results in the seed mass–elevation relationship in a northeastern Tibetan flora. Firstly, these two opposing forces operate simultaneously but overall balance out one another. Secondly, the balance tends to shift toward increased energy-constraints (stress-tolerance) with the increase (decreased) in average seed mass. Thirdly, energy constraints on seed mass is indirect and mediated by the variation in plant height. Finally, plant resource allocation pattern, life-history cycle, and availability of dispersal agents can affect the responses of seed mass to elevation.

Dries Bonte

If  a vector prefers uninfected hosts or infected hosts – how does that affect the pathogen’s spread? Find out in the Early View paper “Vector preference and host defense against infection interact to determine disease dynamics” by Adam R. Zeilinger and Matthew P. Daugherty. Here’s a short version of the paper:

Pathogen spread is greatly influenced by the way that vectors choose which host to feed upon.  Epidemiologists have recognized that many vectors make feeding choices based on whether the host is infected with the pathogen or not.  For example, some mosquito species prefer to feed on animals (including humans) that are infected with malaria over malaria-free animals.  Conversely, the glassy-winged sharpshooter—which spreads the causal pathogen of Pierce’s disease among grapevines—prefers healthy plants.

At the same time, epidemiologists have also recognized that hosts vary in their susceptibility to a disease.  Some hosts are resistant to infection, meaning that the pathogen replicates poorly in them.  Other hosts are tolerant to the disease, meaning that the pathogen can replicate but the host simply does not express disease.  Resistance and tolerance are both forms of defense against a pathogen.

While vector feeding preference and host defense are clearly important for the spread of a pathogen, we were interested in understanding how the two factors may interact to influence pathogen spread.  To begin to understand the relationships between vector preference and host defense, we used a series of mathematical models, similar to SIR models widely used in epidemiology.  The models simulate the spread of a pathogen in interacting host and vector populations under different scenarios for vector preference and host defense.

We found that host resistance curbed pathogen spread, regardless of whether vectors preferred or avoided disease symptoms.  However, differences in vector behavior resulted in highly divergent effects if hosts were tolerant, with the greatest pathogen spread occurring if vectors avoided symptoms.  This occurs because, by masking infection, tolerance causes more vectors to inadvertently come into contact with infected hosts and acquire the pathogen.  Furthermore, we extended our model to a two-patch model, in which two host populations with differing defenses were connected by vector movement.  The outcomes from those scenarios support the idea that host defense impacts pathogen spillover, with a greater potential for tolerant host to be pathogen sources relative to resistant host types.

These results highlight the importance of understanding both vector feeding behavior and the precise form of host defense in predicting pathogen spread.  This may be particularly important for integrated disease management for agricultural crops.  For example, given that the glassy-winged sharpshooter prefers disease-free grapevines, breeding new grapevine varieties that are tolerant to Pierce’s disease may lead to unexpectedly high disease spread among nearby susceptible grapevine varieties.

It’s here! Our new webpage is ready and open for everyone to visit!

Apart from journal information, aims and scopes of Oikos and author guidelines for manuscript submissions, you also find, twitter- and facebook flows, abstracts to newly accepted papers as well as abstracts and links to Early View Papers. The latter with Altmetrics, an article’s impact on the web.

Welcome to visit us at www.oikosjournal.org

The online library is still found at http://onlinelibrary.wiley.com/journal/10.1111/%28ISSN%291600-0706

Submissions are still sent to http://mc.manuscriptcentral.com/oikos

Blog posts will appear both on oikosjournal.wordpress.com, where all old posts are found to, and on our new blog site http://www.oikosjournal.org/blog

We are very happy to announce that “The Per Brinck Oikos Award 2014” has been awarded to Professor Robert D. Holt, University of Florida, Gainsville, Florida, USA.

Here is Bob’s presentation of himself and his research:

“What makes the study of life such an endlessly satisfying endeavor is that species and ecosystems reflect both order and change – both the predictable outcome of general laws, and the lingering effects of idiosyncracies of evolution, earth history, and the often surprising feedbacks that arise in complex natural systems.  As a fan of natural history, I appreciate and indeed relish the complexities and unique contingencies of ecological systems, even as in my role as theoretician I seek for unifying principles.  I have carried out research on a wide range of topics, from food web dynamics and host-pathogen interactions, to habitat fragmentation, to the evolution of dispersal and geographical ranges, and have had the good fortune to have collaborated over my career with many outstanding theoreticians and empiricists.  But in my own mind underlying this diversity of specific topics there is a thematic unity, involving on the one hand a concern with teasing apart the forces driving complex ecological systems, and on the other the desire to integrate perspectives from different disciplines, such as evolution, dynamical systems, and behavior, into our understanding of ecological systems. One approach to ecological complexity is to closely examine the direct and indirect interactions among a small number of interacting species – community modules – which can reveal processes at play in much richer webs of interactions.  Another is to recognize the pervasive influence of spatial heterogeneity and dynamics for almost all ecological systems.  Yet another approach is to recognize the intertwining of ecology and evolution.  For example some taxa are very conservative in their ecological niches, whereas others can evolve rapidly and even explosively over short time horizons.  Understanding all these aspects of ecological complexity, and how they are related over both short and long time-scales, is crucial for addressing a wide range of applied problems, from keeping in check invasive species and emerging diseases, to conserving species in altered landscape, to predicting the impacts of climate change.”

The Per Brinck Oikos Award recognizes extraordinary and important contributions to the science of ecology. Particular emphasis is given to scientific work aimed at synthesis that has lead to novel and original research in unexplorered or neglected fields, or to bridging gaps between ecological disciplines. Such achievements typically require theoretical innovation and development as well as imaginative observational or experimental work, all of which will be valid grounds for recognition.

The /Per Brinck Oikos Award/ is delivered in honor of the Swedish ecologist Professor Per Brinck who has played an instrumental role for the development and recognition of the science of ecology in the Nordic countries, especially as serving as the Editor-in-Chief for Oikos for many years.

The award is delivered annually and the laureate receives a modest prize sum (currently €1500), a diploma and a Swedish artisan glassware. The prize ceremony is hosted by the Swedish Oikos Society. The award is sponsored by the Per Brinck Foundation at the editorial office of the journal Oikos and Wiley/Blackwell Publishing.

Per Brink passed away, at the age of 94 years a few months ago. Read the memorial in Oikos here.

How is lake water quality and nutrient fluxes effected by invasive and native organisms? That’s what Geraldine Nogaro and Alan D. Steinman are answering in the new Early View Oikos paper, “Influence of ecosystem engineers on ecosystem processes is mediated by lake sediment properties”.

Here’s the author’s summary of the paper:

Dreissenid mussels, an iconic invasive species of the Laurentian Great Lakes since their introduction via ballast water in the late 1980s, can greatly alter nutrient fluxes and the microbial food web through their filter-feeding activity and excretion of feces and pseudo-feces at the water–sediment interface. Invasive species may impact biotic community structure, ecosystem processes, and associated goods and services. Their impacts may be especially strong because they also serve as ecosystem engineers (i.e., organisms affecting the physical habitat and resources for other species). The main objective of our study was to determine how the filtering/excretion activity of invasive mussels and the burrowing/bioirrigation activity of native chironomid larvae affect nutrient fluxes and water quality in Muskegon and Bear Lakes (Fig. 1). Laboratory mesocosm experiments were conducted using core tubes filled with sediment, water, and invertebrates (mussels and chironomids) collected from Muskegon and Bear Lakes (Fig. 2).

Fig. 1. Location of Muskegon and Bear Lakes within Laurentian Great Lakes region in Michigan, USA (top). Muskegon Lake (bottom left) and Bear Lake (bottom right) from the sampling boat.

Fig. 2. Dr. Geraldine Nogaro sieving sediment from Muskegon Lake to collect burrowing macroinvertebrates and study their influence on nutrient biogeochemistry in impacted lake ecosystems.

Results showed that sediment reworking and ventilation activities by chironomids increased oxygen penetration in the sediment, affecting primarily pore water chemistry, whereas invasive mussels enhanced nutrient releases in the surface water (Fig. 3). However, burrowing chironomids had a greater influence on sediment reworking and microbial-mediated processes in organic-rich sediments (Bear Lake), whereas invasive mussels enhanced nutrient concentrations in the overlying water of organic-poor sediments (Muskegon Lake). These results have management implications, as the effects of invasive mussels on the biogeochemical functioning in the Great Lakes region and elsewhere can alter system bioenergetics and promote harmful algal blooms.

Fig. 3. Sediment cores used to evaluate invertebrate effects on nutrient release (top). Native chironomids created oxygenated burrows (bottom left), while invasive mussels stimulated nutrient release at the sediment surface (bottom right).

Reference:

Nogaro G., Steinman A.D. (2013) Influence of ecosystem engineers on ecosystem processes is mediated by lake sediment properties. Oikos doi: 10.1111/j.1600-0706.2013.00978.x

How does fruit-eating relate to body size and geographic range? Find out in the Early View paper “Ecological correlates of trophic status and frugivory in neotropical primates” by Joseph E. Hawes and Carlos A. Peres.

Below is their summary of the study:

A good understanding of non-human primate diets in the wild is vitally important for the conservation planning of threatened species, with forest habitat loss and severe forest degradation a major concern throughout the New World tropics. It is also critical to help evaluate the roles of primates within forest food webs, particularly as seed dispersers for tropical forest plants. Fruit eating is widespread amongst primates although they are rarely entirely frugivorous, with insects, gums and leaves providing alternative food sources.

To explore this variation, we reviewed a comprehensive compilation of 290 primate dietary studies from 164 localities in 17 countries across the entire Neotropical realm. Sampling effort varies considerably between sites and species (Hawes et al. 2013), which we accounted for here when comparing the taxonomic richness of fruiting plants recorded in primate diets, and the relative contribution of frugivory to the overall diet. We also found strong evidence to support the long-held hypothesis that body size imposes an upper limit on insectivory and a lower limit on folivory, and therefore that frugivory is most important at intermediate body sizes.

Frugivory continuum in relation to body size, showing a peak in medium-sized primates

One of our most surprising finds was that primates with wide geographic ranges do not necessarily consume a wider diversity of fruits, perhaps because these species tend to be generalist consumers. Another surprise was that primates with higher prevalence of fruit in their diets are among the most poorly studied, meaning we still have a lot to learn about their importance as consumers and seed dispersers in tropical forests.

Image credits:

1. Saguinus oedipus: http://commons.wikimedia.org/wiki/File:Cottontop_tamarin.JPG
2. Pithecia irrorata: © Edgard Collado
3. Alouatta guariba: http://commons.wikimedia.org/wiki/File:Southern_brown_howler_monkey_female_sp_zoo_2.JPG

References:

Hawes, J.E., Calouro, A.M. & Peres, C.A. (2013). Sampling effort in neotropical primate diet studies: collective gains and underlying geographic and taxonomic biases. International Journal of Primatology. DOI: 10.1007/s10764-013-9738-0 (in press).

Who are the murderers and who are the victims in forest soils? Read about Babett Günther and co-workers’ homocide investigation in the Early View Oikos paper: “Variations in prey consumption of centipede predators in forest soils as indicated by molecular gut content analysis”. 

Here’s their story about the study:

We all know from TV series like CSI: crime and murder always happen in the dark, in remote and obscure places where the victim is overwhelmed by the sneakily attacking offenders. Killing is not only confined to humans, and the offender may have some good reason to kill, for example predation and nutrition. But what are the circumstances of successful killing and predation? Are there more killings when there are more/smaller/less defensive victims? Or is it the size of the attacker? Or is it because of the structure and topography of the crime scene?

We tested these hypotheses in one of the most obscure and unearthly environments: the soil and litter layer of different forests. The victims: springtails, dipteran larvae and earthworms. The delinquents: small and large stone centipedes of the genus Lithobius. Just like TV forensic scientists, after rummaging through the dirt, looking for DNA evidence, drinking a lot of coffee and after many long nights in the laboratory, we finally solved the case:

large centipedes are able to kill more prey at high prey abundances and in unstructured environments, while the opposite was true for small predators. Interestingly, small centipedes were also shown to overwhelm large victims, indicating high criminal energy in small creatures, as has been already demonstrated for humans (e.g. John Dillinger).

In a seminal contribution published in 1972 (Nature, 238; 413-414), Sir Robert May showed that from a mathematical point of view the more complex an ecological community is (in terms of the number of species and interactions in the system), the less stable it is. However, complex ecological communities are observed in nature, and so the issue on how species in large complex ecological communities may coexist is still a relevant and open debate in ecology.

In recent years several searched for new principles allowing ecosystems to persist despite their complexity, but a general consensus on this topic has not yet been achieved.

Last summer, an intriguing work published in Science (A. Mougi, M. Kondoh, Science 337, 349) claimed that specific mixture of antagonistic (predator-prey) and mutualistic interactions (beneficial for the interacting individuals) between species is likely to contribute to stabilize ecological communities. Furthermore, they also found that in this type of hybrid community “…increasing complexity leads to increased stability”. As mixing of interaction type is the norm rather than the exception in ecological communities, these conclusions might have led to a final word in the “complexity-stability paradox”.

In our work “Disentangling the effect of hybrid interactions and of the constant effort hypothesis on ecological community stability”, published Early View in Oikos, we show that this is not the case. Indeed, we proved that mixing of mutualistic and predator-prey interaction types does not stabilize the community dynamics and we demonstrate that a positive correlation between complexity and stability is observed only if  species interact so that generalist species (the ones with several “partners”) interact very weakly (in terms of intensity) with respect to specialist species (which have only few partners). We also show that the main findings presented in Mougi and Kondoh work arise as an artifact of the peculiar rescaling of the interaction strengths they imposed. Indeed, using their methodology, the very same effect of ecosystem stabilization may be obtained for generic random ecological networks.

In conclusion, the mismatch between theoretical results and empirical evidences on the stability of ecological community is still there also for communities with a mixing of interaction types, and the “complexity-stability” paradox is still alive. Our work suggest that complexity and stability may be reconciled if a particular scaling of the interactions strength with the species degrees (number of resources) exists, but further studies and experimental evidences are still needed to better understand the role of interaction strengths in real ecological communities.

Samir Suweis, Jacopo Grilli,  Amos Maritan

A sheep increasing 4 times in size, starting to eat competing rabbits! Wow, that would be something! And it’s almost true, at least in the ciliate world! Find out more in the new Early View paper “Trait-mediated apparent competition in an intraguild predator–prey system” by Aabir Banerji and Peter J. Morin. Here’s their short version of the paper:

This investigation stemmed from our earlier work on the inducible trophic polymorphism (ITP) of Tetrahymena vorax.  In the presence of competing ciliates, individuals of T. vorax (starting as small, pear-shaped bacterivores) can completely reconstruct their cytoskeletons and increase their size to up to four times what it was before, becoming spherical predators capable of rapidly phagocytizing their competitors. This transformation occurs within six hours and is completely reversible.  In the figure below, the red arrow points to the cytopharynx (“mouth”) of the predatory morph.

Though there are several real-life ITPs among macroscopic taxa that are roughly analogous to that of T. vorax, I find the fictional example shown below to be slightly more accurate (and fun to present).

While attempting to see which prey we could rear T. vorax on of the ones we had in-stock at our lab, we noticed that T. vorax seemed to get bigger when fed bigger prey.  This is a pattern that has been observed in various other ciliate predators (and a few macroscopic predators), as well.  I was dying to call it “chasmatectasis” (from the Greek words for “gape” and “stretching”) – a term inspired by the way one of my friends in the medical profession had described the phenomenon of competitive eating: “self-induced gastrectasis.”  (Luckily, my labmates talked me out of coining lame phrases at this point.) 

What we really wanted to know was whether this phenomenon could give rise to a novel form of apparent competition (one that was trait-mediated, rather than density-mediated).  Conceptually, this would be like what happens in the Pac-Man video game – eating large prey items allows the predator to eat things it normally would not be able to eat.

As it turns out, it can.

In subtropical and tropical forests up to 90% of woody plant species depend on fruit eating animals for the dispersal of their seeds. Birds are the most diverse and abundant animal group that acts as seed dispersers. Yet, many birds are threatened by the ongoing deforestation and the introduction of alien invasive (non-native and ecosystem-transforming) plant species. It remains a challenge for ecologists to predict how different frugivorous bird species respond to these environmental changes with ultimate consequence for the dispersal service they provide.

Fig 1 Large, undisturbed subtropical forests nowadays are generally confined to protected areas and gorges. On the plains forest extent is heavily reduced by intensive sugar cane farming.

Factors that may drive bird responses to habitat disturbance comprise different dependencies on forested habitat and fruits as resources. Whereas forests specialists only occur in large, undisturbed forests, forest generalists often prevail in smaller fragments, and forest visitors generally dwell in open habitat such as grassland. Similarly, obligate frugivores exclusively feed on fruits to meet their dietary demands, whereas partial frugivores supplement their diets with insects or floral nectar, and opportunistic frugivores only rarely pick some of their favorite fruits.

Fig 2 Forest island within sugar cane. Forest specialists and specialized frugivores are practically absent from such islands.

In our study “Guild-specific shifts in visitation rates of frugivores with habitat loss and plant invasion”, now on Early View in Oikos, we investigated whether changes in visitation rates of bird species (to plants for foraging on fruits) with forest loss and plant invasion can be predicted by their different dependencies on forested habitat and fruits as resources. To do so, we conducted extensive observations of plant-frugivore interactions in a subtropical South African forest landscape. These forests are highly diverse, and more than 700 bird species can be found in the region! However, South African forests are also under increasing pressure from intensive agriculture and urban sprawl, and many invasive plant species have replaced the natural vegetation. Fieldwork was fun but could be tough ­– sometimes we observed no visitor in 18-h of observation! Further, we wore military-style ‘ghillie suits’ for camouflage, a very effective way to hide in dense vegetation and minimize disturbance of birds. However, a woolen suit is a rather poor choice in South African summer…

Fig 3 Trumpeter hornbills (Bycanistes bucinator) are among the largest avian frugivores in South Africa. This individual feeds on fruits of Ficus glumosa.

Fig 5 Speckled mousebirds (Colius striatus) are generalized frugivores which are able to persist in a wide array of differently disturbed habitats. Unfortunately, few fruits on this Tassel-berry (Antidemsa venosum) shrub are fully ripe yet.

Still, the African bird life was totally worth it, and we found highly interesting results. As expected forest specialists were most negatively affected by habitat loss. However, interestingly, obligate frugivores were overall least affected by habitat loss and plant invasion. Fully depending on fruits requires a generalized fruit choice, which seems to make obligate frugivores more robust to changes in habitat conditions. In contrast, visitation of partial and opportunistic frugivores declined – a pattern that can be explained by the comparably more specialized or ‘picky’ foraging behavior of non-obligate frugivores. Specialist foragers were particularly rare when high degrees of habitat loss and plant invasion interacted in synergy.

Fig 4 Testing the ghillie suit in a farmhouse garden. When hiding in even denser vegetation, the observer becomes practically invisible to the avian (and human) eye.

In summary, our study shows that forest loss and plant invasion may especially negatively affect forest specialists and specialized frugivores. This is worrying, as it is those ‘unusual’ species, which by their diverging ecological and behavioral differences from generalized species, considerably contribute to the astonishing diversity of subtropical and tropical forests. Not to forget that most often, they are also wonderful to look at.

Fig 6 These fruits of invasive Bugweed (Solanum mauritianum) show clear marks of pecking frugivores. The plant flowers (background) and fruits at the same time and is able to do so year-round, a significant advantage over many native plant species.

Ingo Grass, Dana G. Berens and Nina Farwig

Congratulations, Jeff Ollerton, Rachael Winfree and Sam Tarrant for passing 100 citations for their paper “How many flowering plants are pollinated by animals?”, published in Oikos in March 2011.

But Jeff, how did you come up with the idea for the paper?

The idea for the paper arose when I was trying to find a solid figure in the literature for the proportion of plants that are biotically pollinated.  It’s an important starting point for any argument about the importance of conserving pollinators, I think: policy makers like to be able to present numbers.   Lots of figures were being quoted, from a range of sources, but once you follow the reference chain back through the papers that cite them you find that numbers which are cited as solid facts disappear into speculation and guestimates.  Like many of the simple and obvious questions, the assumption is that we “know” the answer.  That’s no basis for science-informed conservation policy, but I suspect that it happens all too frequently.

Did you know that the paper would be cited?

To be honest, yes, because a lot of studies and papers are now focussing on the ecology and conservation of plant-pollinator interactions, and our paper provides an initial rationale for why it is important to study them.  But I didn’t appreciate quite how well cited it would be, that certainly took us by surprise:  over 30 citations per year is a high rate in ecology!

Visit Jeff’s blogg:

 

We are very happy to present our cover for 2014! As you might recall, we had a photo competition to find a  nice photo showing ecology in action. And we have a winner!

Congratualtions Prof. Erik Svensson, Lund to the fantastic photo of emerald damselflies!

Here, Erik describes the photo:

The emerald damselfly (Lestes sponsa) is a common insect that is often found mating and ovipositing in the vegetation close to the small ponds where the larvae will later develop. Mating starts with the male clasping a female on her prothorax and so-called “tandem formation”, before sperm transfer. here are two couples (males are green, females are brown) that have formed tandems, and by accident, a chain of our has been formed. The picture was taken in the province of Skåne, (Southern Sweden) in the summer of 2010.

We generally focus on either predation or parasitism. But what happens when we look at the combined effects of the two? Find out in the new Early View paper in Oikos: “Predators and trematode parasites jointly affect larval anuran functional traits and corticosterone levels” by John A. Marino Jr and co-workers. Read their summary here:

In addition to directly causing death, predators can have a range of effects on prey that detect their presence, including altered growth, behavior, and stress hormone levels. These effects may strongly affect how potential prey animals interact with other species. For instance, predator presence may affect interactions between prey species and parasites, which could change the effects of parasite infection on hosts. In our study, we examined how larval dragonfly predators affect the interaction between tadpoles (wood frogs and green frogs) and their parasites in a series of aquaria experiments.

We excluded direct predation by only exposing tadpoles to predator chemical cue (i.e., water from containers holding predators), which has effects on tadpoles similar to actual predator presence. The parasites were a common group of trematodes (flatworms) known as echinostomes, which infect the kidneys of tadpoles. We examined how predator cue affected the response of tadpoles from their first detection of parasite presence to after infection. We found that parasite infection reduced tadpole activity, growth, and survival, and predator cue reduced activity and growth. We also found that the effects of parasites on tadpole behavior, stress hormones, body shape, and development depended on the presence of predators. These effects would be hard to predict by only considering predator and parasite effects separately, which is the case in most studies. Our findings thus emphasize the importance of considering the effects of parasites and predators jointly. The effects we observed are likely important in natural populations and may have important consequences for amphibian conservation. Echinostomes are more abundant near human activities (e.g., agriculture, urbanization), so that their joint effects with other stressors of amphibians, such as predators, are important to understand.

Photo: Ariel Heldt

Science makes progress by applying an experimental approach. This holds in ecology and many of us setup experiments to test the impact of stressors on diversity changes all levels of biological organisation, or how certain treatments affect specific ecological and evolutionary mechanisms. While there have been calls to use experimental approaches to understand eco-evolutionary responses to global change, such approaches often fail because of oversimplification of the real world. On the other side, such approaches allow true replication, a principle condition in science; conditions hardly met using natural experiments. In the forum paper of this month, Janneke HilleRisLambers and colleagues outline that we should embrace ongoing global change (from a scientific point of view only though) as they provide us ‘accidental experiments’ to gain fundamental insight into ecological and evolutionary processes. This is especially true when they result in perturbations that are large or long in duration and difficult or unethical to impose experimentally. While we all agree that such an approach will never replace the experimental method, it is clear that such accidental experiments provide considerable advantages relative to more traditional approaches and are able to provide fundamental scientific insights. HilleRisLambers  et al. provide a forum paper in the best Oikos tradition. A must read!

Synthesis of the paper, as outlined by the authors:

Humans have an increasingly large impact on the planet. In response, ecologists and evolutionary biologists are dedicating increasing scientific attention to global change, largely with studies documenting biological effects and testing strategies to avoid or reverse negative impacts. In this article, we analyze global change from a different perspective, and suggest that human impacts on the environment also serve as valuable ‘accidental experiments’ that can provide fundamental scientific insight. We highlight and synthesize examples of studies taking this approach, and give guidance for gaining future insights from these unfortunate ‘accidental experiments’.

We are also happy to highlight Coreen Forbes’ and Edd Hammill’s research paper as editor’s choice. By making use of an excellent multiple generations dataset, the authors demonstrate the importance of non-consumptive effects on food web dynamics. While the impact of such effects have been demonstrated in simple experiments, the authors moved some steps further and installed experimental microbial communities to seek generality of the available theory and experimental evidence. I would argue that accidental experiments would never allow for insights generated by experimental approaches like these, because, as expected by many, such community level effects appear to be highly context dependent. This context-dependency has here been identified and tested: heterotrophic species that rely on active fouraging to acquire resources are more affected by the presence of predators than other species, especially under conditions of darkness. In short, the paper provides novel, highly relevant insights on community functioning, highlights an unexpected impact of a largely neglected, but overall present abiotic condition by using creative experimental approaches of communities under equilibrium conditions. Clearly work that advances community ecology by targeting mechanisms rather than patterns!

Synthesis of the paper, as outlined by the authors:

Predators affect prey through consumptive and non-consumptive effects (NCEs) such as alterations to prey behaviour, morphology, and life history. However, predators and prey do not exist in isolated pairs, but in complex communities where they interact with many other species. Using a long term study (>10 predator generations), we show that predator NCEs alone can alter community structure under conditions of darkness, but not in a 12h:12h light:dark cycle. Our results demonstrate for the first time that although the community-level consequences of predator NCEs may be dramatic, they depend upon the abiotic conditions of the ecosystem.

I found little to disagree with in the post by Lortie – all very worthy points. I am also very much for placing much emphasis on novelty/creativity/newness. Where we differ, I think, is in the amount of confidence and trust we place upon editors. Having been an editor for many years in several journals in our field, and having been an “author” and a colleague for even longer, I have developed a conviction that the system employed by many journals (where the editorial machinery rates newness without “external” input) is sensitive and imprecise. I was trying to make the point in the TREE article that this is very problematic.

“Newness” is this golden but elusive aspect of a work that, even though we all know exactly what it is, remains hard to define and pin down. I think that everyone that has read Pirsig’s “Zen and the noble art…”, who makes much the same point about “quality”, will be able to relate to this. I am much less optimistic than you are that these qualities allow themselves to be explicitly and objectively defined in a manner which would make them operationally very useful. For this reason, I think that creativity or newness needs to be assessed by (1) initiated, educated and wise readers and (2) several such readers. That is the essence of my point.

Now, in the best of all worlds, we would elect editors that are capable of serving as benevolent and wise dictators who fairly and correctly assess the newness of all submitted manuscripts and rules accordingly. This would certainly improve science and save us all a lot of work. Unfortunately, Dr. Pangloss was, I fear, wrong.

Is invasion biology needed or not? In the Forum paper “A call for an end to calls for the end of invasion biology” by Daniel Simberloff and Jean Vitule continues the discussion, which Valery et al contributed too recently in Oikos. Below is the author’s summary of the paper:

The flood of damaging invasions by introduced species continues, with weekly reports on major invaders, such as Old World pigs in North and South America, Asian hornets in Europe, Asian ladybeetles in North America, Europe, and Africa, African grasses in the Americas and Hawaii, and African catfish in China and Brazil.  This rearrangement of global biogeography attracts public attention primarily when an invader does something dramatic and obvious that annoys humans, as when pigs ravage crops, hornets deliver painful stings, ladybeetles foul wine, grasses foster devastating fires, and catfish invade protected areas preying on native species used in traditional fisheries.  However, the myriad subtler impacts on individual species and on entire ecosystems exact a toll on human interests that is just beginning to be understood as the rapidly growing young science of invasion biology elucidates ever more mechanisms and outcomes of invasions.

The picture is not wholly bleak, however, as scientists develop means of preventing and managing invasions apace with understanding of the scope and scale of their consequences.  A plethora of mechanisms have been brought to bear successfully on damaging invasions, including biological control, chemical herbicides and pesticides, mechanical and physical measures, and a variety of clever specialized approaches tailored to the idiosyncrasies of particular invaders.  Notable recent advances include the use of pheromones to manage invasive sea lampreys in the North American Great Lakes, biological control insects, mechanical methods, chemicals, and inventive use of fire to cut back Australian paperbark in Florida, toxic microbeads to lower zebra mussel densities in water facilities, quick use of chemicals to eradicate infestations of an Australia marine algae in California and a Caribbean mussel in Australia, and eradication of introduced rats by poison baits on islands of ever-increasing size around the world.

Notable in these successes is that, in many cases, researchers did not wait to see what the impacts of the invaders would be, but acted quickly (e.g., the examples of the alga in California and the mussel in Australia).  Almost certainly the opportunity for eradication would have been lost had the scientists focused solely on impacts, rather than on the origin of the invader.  Another important point is that many of these successes (e.g., the paperbark in Florida, the sea lamprey in the Great Lakes, and many island rat populations) were achieved against longstanding invaders that had previously proven intractable.   Also, removal of well established invaders in these cases did not lead to unexpected harmful effects on any native species.

Finally, a few native species, particularly in the wake of various human impacts, behave like invasive non-native species, but harmful impact are far more likely for non-native than for native species.  The argument that fighting invaders and the traditional restoration focus on fostering native species are futile endeavors is contradicted by growing successes in restoration and invasion management.  

Figure 1. Jean Vitule holding a wild-caught African catifish Clarias gariepinus from an Atlanctica forest protected area in Guaraguaçu River, Brazil. Picture taken by Simone Umbria.

To eat or to be eaten-  that’s not always what matters. The importance of non-trophic interactions, such as territorial behavior, in ecological networks, communities and ecosystem studies is dealt with in the new Early View paper “Territorial ants depress plant growth through cascading non-trophic effects in an alpine meadow” by Chuan Zhao and colleagues. Below, you find a summary of the study:

All species are embedded in ecological networks, which are composed of both trophic and non-trophic interactions.  Trophic interactions are well recognized as a major force structuring ecological communities and regulating ecosystem functions.  Meanwhile, although non-trophic territorial interactions between animals have long fascinated behavioral ecologists, their potentially cascading ecosystem-level effects have been largely overlooked.

In our manuscript, we provide one of the first demonstrations of a cascading effect of territorial interactions and, to our knowledge, the very first within the context of a detritus food web. Specifically, in a Tibetan alpine meadow, we experimentally investigated the non-trophic interaction between territorial ants and members of a dung decomposer community, as well as the ecosystem consequences of this interaction. We discovered that ants significantly decreased the abundance of coprophagous beetles and hence triggered a cascade whereby dung removal rates and soil nitrogen concentrations were reduced, ultimately decreasing aboveground plant biomass.

               

Our results show that animal territorial behavior, which is pervasive across animal taxa and ecosystems, can have strong cascading effects and therefore should be explicitly considered in models and experiments linking community structure and ecosystem functioning. Moreover, the results reveal a mechanism through which non-trophic interactions can link animals that do not otherwise interact through more widely studied forms (competition, predation or facilitation).

A recent spotlight paper in Trends in Ecology & Evolution by Goran Arnqvist challenged the notion that editors should use novelty as means to review submissions. This is a very useful contribution to the dialog associated with evolving peer review. It is particularly important for Oikos. A significant aspect of Oikos publications is novel synthesis as described in the mission statement. Consequently, the ability to assess novelty is a necessary skill for editors. In a commentary on this topic, I propose that a solution to this apparent dilemma is to shift the focus from seeking novelty to seeking creativity. This may seem like a subtle semantic shift, but creativity research is a well articulated discipline and is best defined as the combination of novel + useful. I suspect most Oikos editors use some working definition similar to this conceptual framework already.

Chasing creativity may be like chasing the white rabbit in Alice’s Adventures in Wonderland, but we are already down the rabbit hole of peer review and formalizing and discussing how we evaluate the work of others is a positive step forward.

Which species is best for their host marsh cordgrass? Fiddler crab or mussel? The answer is – it depends. As often, both in ecology and everyday life! Read more in the new Early View paper “Independent and interactive effects of two facilitators on their habitat-providing host plant, Spartina alterniflora” by A. Randall Hughes and colleagues. Below is a short summary of the study: And don’t miss the video in the end!

From a distance, salt marshes appear dominated by one (or maybe a few) plant species, such as marsh cordgrass Spartina alterniflora. 

However, there are also many animals residing in the marsh, and prior research has demonstrated that two of these animal species, fiddler crabs (Uca sp.) and ribbed mussels (Geukensia demissa) facilitate the growth and production of cordgrass.  Fiddler crabs create burrows that increase oxygen in the sediment, reducing stress on cordgrass roots.  The fiddler crabs also aerate the sediment during their feeding, and they excrete nutrients that can be utilized by the plants.  Mussels aren’t quite as charismatic as fiddler crabs, but they settle around stems of cordgrass, and the byssal threads that they use to attach to one another and to the sediment can help prevent erosion.  In addition, they excrete nutrients and other organic material as a byproduct of their filter-feeding, and the plants take advantage of these nutrients.

 So who is MORE beneficial for cordgrass, mussels or fiddler crabs?  And is having both species present better than just having one?  Our study suggests that as with much in ecology – it depends.  For one, it depends on what you measure.  If you look at the number of cordgrass stems, then fiddler crabs are the better facilitator – cordgrass with fiddler crabs has higher densities than cordgrass without fiddler crabs, regardless of whether you have mussels or not.  But if you look at plant height (which is correlated with biomass), then mussels are the better facilitator, but only when fiddlers aren’t around.  It also depends on cordgrass genetic identity: some genotypes respond more strongly to the presence of facilitators than others. In the end, the more responses (and genotypes) you include, the greater the benefit of having both facilitator species. 

Over the course of this study, Althea (my co-author and graduate student) noticed high mussel densities in and around sea lavendar (Limonium carolinianum) plants.  She is now exploring this relationship and its implications for our understanding of facilitation more generally.   A good example of how there are always more questions than answers…

 Video link –

http://www.youtube.com/watch?feature=player_embedded&v=htOwL70LKyw

 

Video caption: – This video was produced by WFSU-TV for the In the Grass, On the Reef project.  In the Grass, On the Reef is funded by the National Science Foundation.

 

Photo credits: R. Hughes

Is preprint here to stay? And will it decrease the burden of reviewing?

We’ve seen Peerage of Science, F1000 research and PeerJ. And here’s the next preprint server, for biological manuscripts only, BioRxiv, which you can read more about on Science Insider:

http://news.sciencemag.org/biology/2013/11/new-preprint-server-aims-be-biologists-answer-physicists-arxiv

A problem might be that the journal targeted for final submission might not allow submissions of manuscripts that have already been shared online.

We are happy to announce that Oikos welcomes submissions of manuscripts that have been “published” on those preprint servers.

Here is a list of journal policies in the matter:

http://en.wikipedia.org/wiki/List_of_academic_journals_by_preprint_policy

So will you share your next manuscript online to get comments during the writing process?

In the new Oikos Early View paper, “Inferring temporal shifts in landuse intensity from functional response traits and functional diversity patterns: a study of Scotland’s mach air grassland”, Rob J.Lewis and colleagues explore how land use changes affect community assembly processes. Here’s Rob’s summary of paper:

There is a growing consensus among ecologists that a trait based view on species community composition may far outweigh the utility of one solely centred on taxonomic composition in explaining the structure and function of ecological communities. Such a shift in focus has resulted in a considerable increase in the number of scientific studies examining links between individual traits and the environment. In the realm of plant ecology, particular traits have been shown to respond consistently to changes in the environment. Collectively, these traits are termed plant functional response traits and are increasingly used to explain how plant functional composition responds to environmental change, particularly along environmental gradients of disturbance.

In this study, we utilise an a priori knowledge of how plant functional response traits linked to disturbances such as grazing intensity, agricultural intensification and land-use abandonment to infer land-use drivers of temporal change (over ca. 30 years). We also adopt relatively new metrics to derive composite indices of functional diversity to investigate shifts in community assembly mechanisms over time. Moreover our approach was applied to a national-scale temporal vegetation dataset of a globally rare semi natural grassland termed ‘Machair’, an extremely complex, species-rich, costal dune plain of ecological and cultural importance

Baseline data was derived from the Scottish Coastal Survey first collated in the mid 1970’s by the Nature Conservancy Council (NCC), with the aim to identify ecologically important and sensitive areas of Scotland’s soft coast (i.e. low lying coastal areas composed of sand, shingle or mud). Records included data on plants, habitats, environment and land-use of circa 4000 vegetation plots. As part of the lead author’s PhD thesis, we performed a re-survey of this dataset between 2009 and 2010, focusing specifically on sites known to include Machair, providing temporal data for most of the western and northern seaboard of Scotland.

This paper, the first of a series that make use of this unique dataset for investigating temporal patterns of change, discusses the observed shifts in functional traits and functional diversity indices over time, the potential causations driving these relative to land-use practices on the Machair, and the utility of our methods for inferring temporal drivers of functional compositional change.

Recently I published an analysis of the extent to which the ecological literature engages with theory (http://onlinelibrary.wiley.com/doi/10.1111/ele.12196/abstract). One part of that analysis was a comparison of current journals. Among the ecology journals, Oikos scored the highest with 73% of the papers in the 2012 June and July issues including some aspect of theory development or testing. But we can all do better. Here are some ways to increase the theory engagement of your papers.

First ask yourself, “What theory does my paper relate to?” Even if your paper is a description of some system, that description must relate to the facts that underpin some theory. Theories rely on generalizations. Does this particular instance help strengthen a generalization? Does it dispute a generalization? Is the state of knowledge such that generalizations are uncertain? If so, how does this paper reduce that uncertainty? Then make that theory and those generalizations guideposts for the entire paper.

But you say, “There is no formal theory for this question, just a general understanding.” That general understanding is the theory, it simply lacks formalization. In the parlance of the theory structure presented by Mike Willig and myself, no constitutive theory exists. Here is an opportunity for you to create one. Formalizing a constitutive theory is not difficult. For examples of how to do this, see our book (Scheiner and Willig. 2011. The Theory of Ecology. University of Chicago Press). If there are already numerous models relating to the topic, it is an exercise in finding their common threads. That is the process that we went through with our first constitutive theory (Scheiner and Willig. 2005. Am. Nat. 166:458-469). For more nascent fields, you may have to work a bit harder to discern those threads. In the end you will have a list of rules and generalization (“propositions” in our terminology) against which to compare your data.

As a reviewer of papers, ask if a paper engages in theory right at the beginning. My tally of “no theory” papers included many for which formal theories exist, but no explicit connection was made. Make sure that this happens. If the introduction of the paper does not explicitly name a theory, insist that it do so. We should be asking more of ourselves. Ecology is a mature discipline rich in theories. Our science will only be strengthened by all of us doing more to engage with theory and insisting that our colleagues do likewise.

Last week, EiC Chris Lortie presented the editor’s choice papers for the November issue. Below you find the nice figure and table from one of them, “Dispersal and species’ responses to climate change”, by Travis et al. And remember, Editor’s choice papers are freely available online throughout the month!

Table 1: Effects of climate change on individual dispersal. Climate change is predicted to lead to lower windspeeds (A), higher temperatures (B), increased frequency of storms (C), flooding (D), reduced snow cover (E), and changed rainfall (F) (1, 2). Each of these climatic factors has been shown to affect dispersal in a range of organisms, either through a direct impact on the individual during dispersal, or indirectly by altering the biophysical environment or the state of the dispersing organism. Key empirical examples of these effects are described with the arrow (    decrease;     increase) describing how predicted changes in specific climatic factors would alter the propensity to emigrate or the distance dispersed during transfer.

Figure 3: Dispersal will be the heart of a new generation of process-based models developed to predict, and inform the management of, species’ responses to environmental change. By incorporating dispersal together with an explicit representation of population dynamics, models will become much better able to simulate the spatio-temporal dynamics of species under alternative future climate and land-use scenarios. To date, most projections of biodiversity responses to climate change have been made using all or nothing dispersal with fewer examples of nearest-neighbour dispersal or statistical dispersal kernels. While more detailed mechanistic dispersal models have been developed both for animal and plant dispersal, they have yet to be used extensively in the climate change field. In part this is due to the substantial challenges faced with these more sophisticated models, both in terms of the data needs for parameterisation and the greater computation needs of these more complex approaches. We argue that incorporating greater realism in the dispersal process will result in improved predictive capability, particularly when there are likely to be synergistic impacts of climate and land use change.

[Image credits: Corine Land Cover (land cover map); Wordclim (climate map); James Bullock (bustard); María Triviño (observed and predicted maps of bustard distribution)]

A few days left to submit your ecology-photo!

Will your photo be on the Oikos cover 2014?

We seek photos illustrating the Oikos’ goal of Synthesising Ecology or demonstrating ecology in action (e.g. processes or interactions), not only a single organism or a landscape.

Please send your photos together with the  oikos-photo-competition-form14 to oikos@oikosoffice.lu.se, with Photo competetion as subject, before November 10th 2013. The winner will be awarded a book price from Amazon for a value of 100 Euro. The winning photo will be at the cover of all issues of Oikos from during 2014.

Competition Rules:

Entries must be digital images, submitted electronically, in jpg or tiff-format. Images must be available in 300 ppi.

Digital enhancements must be kept to a minimum and must be declared. Both the original and the enhanced image must be submitted.

File names must include appplicant’s surname.

Photos must be accompanied by an entry form that describes illustrated species and scenes. Download the oikos-photo-competition-form14

A prize committee consisting of Managing Editor, Editor in Chief, deputy editors, Technical Editor of Oikos and the Director of the Oikos Editorial Office, will judge which photo that best suits our requests. The decision by the committee is final.

All submissions will be entered under a Creative Commons License and will be displayed on Oikos webpage and social media and may be used  for commercial purposes. Download Creative Commons License here.

Oikos takes no responsibility for submitted images being lost, damaged or dealyed.

How herbivores and nutrient interact in grassland communities is studied in the early View paper “Multiple nutrients and herbivores interact to govern diversity, productivity, composition, and infection in a successional grassland” by Elizabeth T. Borer and co-workers. Here’s Elizabeth’s summary of the paper:

We have all heard about the health benefits of a balanced diet, and it turns out that nutritional balance matters in ecosystems, too. While most research examining nutrient effects on ecosystems has focused on one or two nutrients, such as nitrogen and phosphorus, humans are concurrently changing the supply rates and ratios of many different nutrients, creating the possibility for complex effects on ecosystems and the services they provide.  We found that the ratio of nitrogen to phosphorus supplied to a grassland ecosystem had larger impacts on infection by a common crop disease than any single major nutrient alone. Grassland net production increased with nitrogen fertilization, but consumption of plants by a common grassland herbivore, the pocket gopher, caused net grassland production to decline with fertilization. Single factor studies would not have uncovered these and other relationships even though such relationships are critical for effective predictions of biodiversity and ecosystem functioning in a world in which human activities are simultaneously changing herbivore abundance and the relative supply of many growth-limiting nutrients.

Indirect interactions are one of my current favorite topics. So fascinating, so elusive, simple in theory, but easily construed. This was the second editor’s choice for November:

Alexander, M. E., Dick, J. T. A. and O’Connor, N. E. 2013. Trait-mediated indirect interactions in a marine intertidal system as quantified by functional responses. – Oikos 122: 1521-1531.

doi: 10.1111/j.1600-0706.2013.00472.x

Trait-mediated indirect interactions are tested in a highly tractable system in this study. However, a very elegant experimental design was executed to explore whether habitat complexity was important to the functional response expressed by predators. Three species were used in total (2 predators and 1 prey species) and experimental arenas were used (Fig 1). Diet cues and responses to the other species were examined in petri dishes with stones glued to the bottom.  Very clever! I would love to see a real photo of the design or videos of the various activity levels reported.

Novel synthesis
This study was an example of novel synthesis for the following reasons.
The design was superb.
The ideas, terms (such as density-mediated indirect interactions versus trait mediated), and predictions were extremely well developed and very precise.
Simple versus complex habitats was tested thereby addressing a major and ongoing theme of context dependence in ecology and evolution.
Density and indirect interactions are well modeled in the study.

Ecologically, the findings were significant in that habitat complexity is shown to mediate population stability. Super simple spoiler: in simple habitats, trait-mediated indirect interactions may destabilize prey populations whilst in complex habitats regulation of intermediate consumers may promote prey stability. Fantastic. I wonder how we could apply this approach to terrestrial systems.

Amphipoda (not actual size):

 

Sample petri dish arenas in general:

Will climate change ever have positive impacts 🙂 In many respects, climate change and invasive species both challenge our notions of community assembly and the relative importance of various drivers in structuring both populations and communities. For the first editor’s choice for November, we selected the following paper.

Travis, J. M. J., Delgado, M., Bocedi, G., Baguette, M., Bartoń, K., Bonte, D., Boulangeat, I., Hodgson, J. A., Kubisch, A., Penteriani, V., Saastamoinen, M., Stevens, V. M. and Bullock, J. M. 2013. Dispersal and species’ responses to climate change. – Oikos 122: 1532-1540.

doi: 10.1111/j.1600-0706.2013.00399.x

Rationale & novel synthesis
Dispersal describes a fascinating set of processes in ecology and evolution. However, the semantics are not that well articulated. In this article, the terminology and scope of dispersal is well developed. Importantly, the capacity for dispersal to evolve under climate is examined and the reciprocal concept, how dispersal should be included in predictive models is also summarized. The direct and indirect causes of changed dispersal are summarized with an excellent graphic, and the predicted impacts on emigration and transfer phases are provided separately. A central role for dispersal is proposed for considering the climate change versus land use drivers on the realized population dynamics. I like this idea. I am not an dispersal expert at the scale but this seemed like a very reasonable,if not challenging, novel conceptual model.

Five priority areas for conservation are identified.
1. Protocols must be developed to gather/aggregate high-res datasets on dispersal at all scales.
2. Mechanistic movement models and more realistic models in general must now be used.
3. Predictive models must now included more nuanced handling of within species variation.
4. Include relationships between evolution and dispersal in models when examining trait sets (and plasticity, selection processes, etc).
5. Use models to most effectively intervene in managed dispersal processes.

A new method to measure the strength of trade-offs is presented and tested in the Early View paper “A standardized approach to estimate life history tradeoffs in evolutionary ecology” by Sandra Hamel and co-workers. Here’s Sandra’s summary of the paper:

A major goal of life-history studies is to understand how natural selection shapes individual fitness-related traits, such as growth, reproduction, and survival. So far, a large number of studies have demonstrated the occurrence of many trade-offs (e.g. number vs. size of offspring, age at first reproduction vs. longevity), but most researches have concentrated on detecting trade-offs – that is answering “yes” or “no” to the question “Is there a trade-off between trait A and trait B”. Although these studies are fundamental because they have provided substantial empirical evidence for the existence of trade-offs, they are somewhat limited. For instance, if we wish to understand how different life-history strategies evolve among different species, among populations of the same species, or among individuals of the same population, we need to be able to tell not only whether there is or not a trade-off, but most importantly what is the strength of this trade-off.

Measuring the strength of a trade-off would be highly valuable for determining its relative importance. For example, to determine whether the trade-off between current and future reproduction is stronger in shorter- vs. longer-lived species, we need to measure the strength of this trade-off in different species. Within a single species, we might also want to determine whether trade-offs among growth and survival traits are stronger than trade-offs among growth and reproductive traits, which could allow us to better understand where the strongest selection pressures occur.

Our paper therefore presents a method to measure the strength of trade-offs. Although some methods have been used previously to quantify trade-offs, these methods cannot be applied with respect to binary traits – that is traits usually described by “yes/no”. Indeed, analyses of binary data present many analytical issues and thereby are more complex and often more limited compared with other types of data. Nevertheless, binary traits are central in life histories (e.g. probability of reproduction, nesting success, offspring survival), and so we need a method that can be applied to any type of traits to be able to compare the importance of different life-history trade-offs. Our paper provides such a standardized approach, which also accounts for the confounding effects of both environmental variation in resource availability and individual heterogeneity.

We illustrate the large potential of our approach by applying our method to longitudinal data from roe deer and mountain goats. Out of seven trade-offs measured, the strongest was observed between current and future parturition in mountain goats, a capital breeder, whereas this trade-off did not occur and rather showed a weak positive effect in roe deer, an income breeder. Although the trade-offs presented are only a few examples in two species, they suggest that the between-species differences might result from different tactics of energy allocation to reproduction. Most importantly, these examples illustrate how our method can be used to compare the relative importance of different trade-offs, and how it opens the door to a deeper understanding of the evolution of life-history traits in free-ranging populations.

The pictures represent the two species used in the examples. On one picture we have a 14 year-old mountain goat female nursing her kid. On the other picture we have a roe deer female that is being checked for pregnancy with an ultrasonic scanner seen in the background.

Plants that make active decisions? Read more in the Early View paper “Informed dispersal in plants: Heterosperma pinnatum (Asteraceae) adjusts its dispersal mode to escape from competition and water stress” by Carlos Martorell and Marcella Martinez-Lopez. Here’s their summary of the paper:

We all know someone who has migrated to a wealthy country because social or economic conditions in her/his homeland are harsh. Among animals the same phenomenon occurs, sometimes taking the form of huge migrations away from areas that are seasonally adverse because they are too cold or too dry. But what about plants? We all know that plants can move from one place into another when they are seeds, but it would appear that they are unable of judging whether it is profitable to stay in their natal site or to migrate in search of a better place. To do so, plants, like animals, need to gather and process information about their environment. The small annual plant Heterosperma pinnatum does exactly so. When the environment in which it grows is too dry, it promotes the long-distance dispersal of its seeds. The same happens in crowded areas where competition for the available resources is strong. In this way, its descendants may find more favorable places to live in. The mechanism is quite simple: H. pinnatum produces two different kinds of fruit, one that has hooks that become attached to animal fur and thus can travel very large distances, and another kind that lacks dispersal structures and thus remains in the close vicinity of the mother plant. By regulating the proportion of each type of fruit depending on environmental conditions, this plant is able to decide whether its descendants will continue to exploit the local resources or else face the risks of long-distance travel in search for a place where they may have better chances to survive and reproduce.

Different fruits of Heterosperma pinnatum. Left: an unawned fruit of the type that usually remains some 10–20 cm from the mother plant. Right: a fruit with awns on top of a long beak that projects away from the mother plant. When an animal passes by, the exposed awns become attached to its fur and the fruit is dispersed over a long distance. Middle: an intermediate fruit with awns but no beak. Photo: LFVV Boullosa.

Does new-density increase or decrease predation rate? Find out in the new Early View paper “Adaptive nest clustering and density-dependent nest survival in dabbling ducks” by Kevin M. Ringelman and co-workers. Here’s Kevin’s summary of the paper:

Many wildlife populations are regulated by density dependence: when populations become very large, survival and recruitment rates tend to decline.  In North American waterfowl, density dependence is often observed at continental scales, and nest predation has long been implicated as a key factor driving this pattern.  Predators may aggregate in areas of high nest density, and can reduce nest success to the point where it limits population growth.  However, despite extensive research on this topic, it remains unclear if and how nest density influences predation rates.  Part of this confusion may have arisen because previous studies have examined density-dependent predation at relatively large spatial and temporal scales.  To address this, we used three years of data on nest survival of two species of waterfowl, Mallards and Gadwall, to more fully explore the relationship between small-scale patterns of nest clustering and nest survival. 

Throughout the season, we found that the distribution of nests was consistently clustered at small spatial scales (~50 – 400 m), especially for Mallard nests, and that this pattern was robust to yearly variation in nest density and the intensity of predation.  We also showed that nests within a cluster had lower predation rates, which runs counter to the general assumption that predators are attracted to areas of high nest density.  Because the predators at our study site probably only depredate duck nests incidentally, nesting a group could effectively dilute predation risk from predators that are “just passing through.”

How density effects reproductive success and extra pair-paternity is studied in the new Early View paper “Form, function and consequences of density dependence in a long-distance migratory bird” by Ann E. McKellar and co-workers. Below is Ann’s summary of the study:

The negative effects of an increasing population density on reproductive output have long been recognized in many animals, including migratory birds. As breeding density increases, territory sizes generally decrease, causing crowding and increasing neighbour-neighbour interactions, which can lead to decreases in rates of foraging and chick feeding, and increases in rates of nest predation. Such density-dependent processes can thus produce negative feedbacks which contribute to population regulation and the general stability of population size, since periods of high population density will reduce overall breeding success, and vice versa.

Moreover, population density can affect mating tactics. Rates of extra-pair copulations often increase with population density, thus providing an additional challenge to the reproductive fitness of males residing in dense areas.

Interestingly, the density dependence of demography and behaviour are rarely studied simultaneously. And yet such a holistic view is important because individual behaviours can influence population demographics, which can then feed back into the success of individual behaviours. These types of behavioural-demographic loops are no trivial matter, as modeling exercises have shown that they may influence the probability of population extinction.

We examined the density dependence of reproductive success and extra-pair paternity at a long-term study site of breeding American redstarts in Ontario, Canada. We found that greater breeding density was associated with reduced reproductive success, likely as a result of increased nest predation, and increased rates of extra-pair paternity. Overall, these findings contribute to a broader understanding of the selective pressures and regulatory mechanisms acting on migratory birds, from the individual up to the population level.

The resilience of eco systems is studied in the new Early View paper “A new approach for rapid detection of nearby thresholds in ecosystem time series” by Stephen R. Carpenter and co-workers, in Oikos. Below is Stephen’s summary of the study:

When is the disappearance of a fish population like a missile attack? During the Cold War, scientists developed sensitive methods for detecting the radar signature of incoming missiles. More recently, ecologists have discovered that ecosystems display statistical signatures of changing resilience. The evidence of changing resilience is found in detailed observations that can be automated, like the signals from a radar installation.

Changing climate, land use, or chemical pollution can be as harmful to ecosystems as a missile impact. Gradual changes in climate  or other factors can erode resilience and lead to catastrophic changes. Conversion of a rangeland to a desert, collapse of a fishery, or explosion of toxic algae in a lake are accompanied by loss of resilience as an ecosystem is driven past a critical threshold.

When a complex system approaches a critical threshold, its behavior becomes more variable. Close to the threshold, resilience is low and variability is high. Therefore it might be possible to infer changes in resilience from changes in variability.

Research on lakes has shown that water chemistry, concentrations of algae, and even movements of animals become more variable as resilience declines. Some of these changes can be measured by new technology, such as the instruments mounted on the buoy shown in the photo

Our research team adapted the missile-detection methods to data from a lake that was manipulated to drive it slowly over a threshold. We gradually added largemouth bass to the lake to erode the resilience of minnows and other small fish that are prey to the bass. We found that variability increased in spatial pattern of minnows, abundance of small grazing animals in the water, concentration of algae, concentration of oxygen, and acidity of the water. In the Oikos paper, we applied the method to time series of chlorophyll, which is related only indirectly to the change in the fish. The growing variability of chlorophyll was the equivalent of a missile image on a radar screen.

About a year after the rising variability was detected, the old food chain of the lake collapsed and was replaced by a new food chain. The new food chain had no minnows, abundant grazers and very low concentrations of algae.

Although largemouth bass and missiles are quite different, both of them can completely transform their targets. The research shows how insights from one area of science can be applied in a new way. Perhaps missile-detection methods will one day monitor the resilience of lakes and other ecosystems in a changing world.

In the Early view Oikos paper “Where am I and Why? Synthesizing range biology and the eco-evolutionary dynamics of dispersal”, Alexander Kubisch, Robert D. Holt, Hans Joachim Poethke and Emanuel A. Fronhofer investigate the emergence of species’ geographic ranges and the many different forces acting on it. Here is their summary:

The distribution of species in space and time is one of the oldest puzzles in ecology. Already Charles Darwin pointed this out over 150 years ago, when he asked: “Who can explain why one species ranges widely and is very numerous, and why another allied species has a narrow range and is rare?” (Darwin 1859). And still, although much research has been invested into that topic since the times of Darwin, we still do not comprehensively understand the formation of any given species’ range.

In this paper we provide an overview of the manifold eco-evolutionary forces, which – in a metapopulation context – determine the formation of species’ ranges. Based on the idea that colonizations and local extinctions are the crucial determinants of an emerging range limit, we highlight the importance of dispersal evolution in this context. It is well known that dispersal of species is highly plastic and subject to strong evolutionary changes. However, this fact is still often ignored when distributions of species are investigated. To clarify the influences of dispersal on range formation, we organize relevant forces acting on all hierarchical levels, ranging from the landscape via genes, individuals and populations to communities, in a framework. In combination with novel simulation results this synthesis brings together the multiple interactions between these factors and forces, which may lead to high levels of complexity and non-linearity.

This contribution will build the core of an upcoming virtual special issue of Oikos, in which a compilation of studies on several aspects affecting range formation and spatial ecology will highlight and summarize the described complexities and non-linearities, which challenge our understanding of species’ distributions. Synthesizing the factors and forces affecting range formation and highlighting the importance of dispersal evolution will surely prove to be helpful in advancing our knowledge and mechanistic understanding of species’ geographic ranges.

How species associate with each other and other co-ocurrence patterns have been studied by Mahi Puri and colleagues along the west coast of India. Read the new Early View paper here:  “Multi-scale patterns in co-occurrence of rocky inter-tidal gastropods along the west coast of India”

Below is a short summary by Mahi Puri:

The study was carried out as a Master’s thesis, which meant it had to be completed within a period of 6 months. The fieldwork component was only half of that duration! Having previously never worked on marine and inter-tidal fauna, I was eager to learn about this ecosystem. Most of the classical literature on intertidal fauna is based on experimental work to determine relationships between different taxa and species, done at patch level or small spatial scales. Unfortunately there has been little such work on marine ecosystems in India, though it has a really long coastline (8100 km); most of the work is either descriptive in nature or based on physiological condition affecting the distribution of species. I was interested in looking at association patterns among different species at the community level at much broader scales (essentially examine pairs of species that competed or co-occurred with one another), incorporating the expanse of the Indian west coast.

Because of the large scale of the study and the fact that we were dealing with the entire community and not just a few select species, it was not logistically feasible to incorporate experiments in this study. Based on Jared Diamond’s work on assembly rules and Nicholas Gotelli’s analytical approach (i.e. null model analysis) which did not require experiments to assess association patterns among different species, our study was designed to cover 12 sites spread across nearly 1100 km of the Indian west coast. All the study sites were rocky beaches and we looked at gastropod species occupying these rocky intertidal habitats.

We found non-random patterns of species association at large spatial scales indicating that community assembly is not determined by random factors such as tidal drift. Most pairs of species competed with one another, although the pairs with significant associations co-occurred. We also found pairs of some species displaying different association patterns in different locations i.e. they competed in some locations but co-occurred in others. This study highlights the importance of examining general patterns and of using observational studies to gain insights at multiple scales.

What effect does the moon actually have on us? And on animal populations? Find out more in the new Early View paper “Linking ‘10-year’ herbivore cycles to the lunisolar oscillation: the cosmic ray hypothesis” by Vidar Selås. Below, is Vidar’s summary of the study:

The famous “10-year” population cycles of the snowshoe hare and its specialist predator, the Canada lynx, are commonly interpreted as a combined effect of predation and overgrazing. However, these mechanisms cannot explain the consistent cycle period. Herbert Archibald showed that the mean cycle period is 9.3 years, corresponding to the half period of a full 360° rotation of the Moon’s orbital plane. The same period is apparent in a 120-yr time series for the autumnal moth in Fennoscandia and an 1145-yr time series for the larch budmoth in the Alps.

According to Thomas C. R. White, stress factors that require increased mobilization of proteins in plants may increase protein availability above the critical threshold for herbivores. As pointed out by Charles H. Smith, hare cycles are most pronounced in areas with low protection against cosmic rays. Because repair of damages caused by cosmic rays require protein mobilization in plants, and cosmic ray fluxes are affected by the position of the Moon, cosmic rays may be the link between the lunar and herbivore cycles.

Cosmic rays are high-speed charged particles (mainly protons), which are deflected by a sufficiently strong magnetic field and absorbed by a sufficiently thick air layer. The protection provided by the Sun’s magnetic field, which reaches far beyond the Earth’s orbit, fluctuates with the 11-yr solar cycle. The protection provided by the Earth’s magnetic field decreases from equator to the magnetic poles, whereas the protection provided by the Earth’s atmosphere decreases with elevation.

In the atmosphere, secondary cosmic rays are created by collisions between primary cosmic rays and air molecules. Because the most important secondary cosmic rays, muons, are short-lived, only protons with sufficiently high speed are able to produce muons that reach the ground. When eclipses occur close to solstice, which happens at 9.3-yr intervals, the Moon enhances the Sun-Earth magnetic connection, so that more solar energetic particles hit the Earth’s magnetic field. This results in increased temperatures and an expansion of the atmosphere, making it more difficult for muons to reach the ground. The effect of the Moon is probably most important in areas where the protection against cosmic rays is low. In areas with better protection, the 11-yr solar signal would be expected to prevail.

A new theoretical model to better study of the role temperature variability plays on individual performance and population dynamics, is presented in the new Early View paper “The role of temperature variability on insect performance and population dynamics in a warming world” by Sergio A. Estay et al.

Watch Sergio’s summary of the study on Youtube:

http://www.youtube.com/watch?v=9_Pbmb8n4zk&feature=youtu.be

Can ecological patterns be organized in a “Periodic table”? Find out in the Early View paper  “Ecological periodic tables: in principle and practice” by  Steven P. Ferraro.

Watch Steven’s talk about it here:

http://my.brainshark.com/Periodic-Tables-PeerOvation-486260509

and look at the slides from a talk about it here:

http://f1000.com/posters/browse/summary/1092512

What body condition index is best? Studied for mice in the new Early View paper by Marta K Labocha and co-workers. Below is a summary by Marta:

In humans, BMI (or the body mass index) is a widely used indicator of a person’s body fat.  In animals other than humans, body fat is also important because animals with more fat typically have greater energy reserves which may allow them to better cope with stressful conditions.   In animals, these indicators of body fat (and sometime other indicators of animal quality) are called condition indices.  These condition indices are typically determined from body measurements, but exactly which measurements to use is both unclear and a topic of keen interest.  Many conditions indices are used without being tested for their accuracy.  To test these indices, we compared how well a broad range of body condition indices predicted body fat content in mice Mus musculus. We also compared the performance of these condition indices with a statistical technique, multiple regression of several morphometric variables (body measurements) on body fat content. Multiple regressions incorporating pelvic circumference (i.e., girth at the iliac crests –around the widest part of the hips) were the best predictors of body fat content and were better than any of the condition indices. So, perhaps not surprisingly, mice with bigger waists are fatter.  What is surprising is that this method has not been used before for mice.  Our results suggest a way to improve condition mass indices for mice, and our methods may be useful for other animals as well.

Read Justin Travis’ and co-workers’ Forum paper “Dispersal and species’ responses to climate change” in Oikos Early View. Below is Justin’s background story to the paper:

Over the last decade or so there have been a series of meetings and workshops involving individuals interested in a broad range of issues related to causes and consequences of dispersal. These have involved people focused on a range of animal and plant systems, adopting field and lab based approaches and also including people developing models for theory and also for prediction. One of the group’s recent meetings took place immediately after the European Ecological Federation Congress in Avila held in 2011. Maria Delgado had organised a casa for us in a tiny village called Tabladillos, close to Segovia. Our objective was to collectively evaluate how dispersal is likely to be impacted by climate change and also how dispersal, and changes in dispersal, are likely to impact species’ responses to climate change.  After an excellent few days, full of interesting discussion, plenty of relaxing in the sun, BBQs and fine Spanish wine (see photo 2) we left with a first rough draft of a manuscript and a long list of allocated tasks.

Is the Oikos chief editor the only one working? Dries is busy handling manuscripts while James and Maria dream of seeds and eagle owls, respectively!

Kamil’s photographic trickery captures the group enjoying an evening meal!

The final result of this team effort (see photo 3) is now published by Oikos http://onlinelibrary.wiley.com/doi/10.1111/j.1600-0706.2013.00399.x/abstract and we hope it serves to emphasise just how important it is to increase our understanding of the eco-evolutionary dynamics of dispersal under climate change for understanding how species will fare over the coming decades.

The workshop participants with our canine mascot, Karhu!

We argue that it is particularly important that conservation actions are founded on a better understanding of dispersal. There is already a large body of knowledge on this key process that can inform current management plans but important knowledge gaps remain where future research is required. Finally, not wanting to miss an obvious chance for advertisement, the next meeting organised by the informal dispersal working group will be in Aberdeen in November. It will take the form of a conference and the objective of this meeting is to seek greater integration both between the fields of dispersal ecology and movement ecology and also between researchers working in terrestrial and marine systems (see http://www.abdn.ac.uk/events/mad-2013/ for details).

 

How the mass of plant seeds change with altitude is studied in the new Oikos Early View paper “Disentangling ecological, allometric and evolutionary determinants of the relationship between seed mass and elevation: insights from multiple analyses of 1355 angiosperm species on the eastern Tibetan Plateau” by W. Qi et al. Below you find some photos from the field work and a short story by the authors:

In each summer and autumn during 2001-2008, Wei Qi, Guozhen Du and their colleagues collected seeds (Fig. 1, Wei Qi is collecting seeds; Fig. 2, Guozhen Du is collecting seeds), collected plant specimens (Fig. 3) and recorded elevation and habitat information (Fig. 4) on the northeastern verge of the Tibetan Plateau in China (101°05′-104°40′ E, 32°60′-35°30′ N). Here, you can see towering mountains (Fig. 5), grotesque rock formations (Fig. 6), crystal clear waters (Fig. 7), dense forests (Fig. 8), beautiful meadows (Fig. 9) and magnificent temples (Fig. 10). Seed collection is a hard work. Sometime, we had to climb cliffs (Fig. 11) or to ride horses (Fig. 12). Moreover, in order to save time to collect seeds, we often ate cakes in the car (Fig. 13) or drank beer under the snowy mountain (Fig. 14). In spite of this, we are always happy (Fig. 15), because we belong to a cohesive group (Fig. 16).

For the September issues, we chose the forum paper of Caplat et al. as editor’s choice. The paper arose from a special symposium at the 2011 ESA meeting in Austin, and synthesizes how insights from invasion ecology can help us understanding species responses to climate change. The paper does not aim to provide a systematic review or meta-analysis of the literature, but instead focusses on the useful concepts and insights generated from invasion processes relevant to climate change ecology of plants. The authors particularly focus on processes related to movement and especially the settlement phase and the expected impacts of altered species distributions on recipient ecosystems. While Oikos does not have a special focus on applied ecological research, we do stimulate the translation of fundamental insights into a global change or societal context. This appears especially important in the context of species management, both with respect to conservation and control under future scenarios of climate change.

 

Polley and colleagues report that plant functional traits improve diversity-based predictions of temporal stability of grassland productivity. The study uses measures of aboveground net primary productivity from an 11 years lasting experimental study in Texas.  The authors varied levels of species richness and abundances of perennial grassland species and assessed how species abundance patterns and functional traits linked to the acquisition and processing of essential resources could be used to improve richness-based predictions of community stability. The system showed large fluctuation in annual precipitation inducing shifts in the plant community responses. Results indicate that the temporal stability of grassland primary production may depend as much on species abundances and functional traits linked to plant responses to precipitation variability as on species richness alone.

In this video, Stuart Auld tells you about his and his colleagues’ study on parasite’s seasonal variations, now published Early View in Oikos

http://youtu.be/NugHfU8Z_NU

and here’s the paper:

Rapid change in parasite infection traits over the course of an epidemic in a wild host–parasite population

Want to read more about Stuart’s research? Here’s his webpage:

www.stuartauld.wordpress.com

and check him up at twitter:

@StuAuld

Look up for the must-reads on the global biogeography of autotroph chemistry (Borer and colleagues) and litter decomposability of temperate rainforest trees (Jackson and colleagues). These are two different synthetizing contributions by reviewing the current state of the art and using an integrated, multispecies research approach.

Clearly, such contributions enhance our understanding of ecosystem functioning.

In the Early View paper “Rapid change in parasite infection traits over the course of an epidemic in a wild host–parasite population”, Stuart Auld and colleagues examines how parasite traits vary during an epidemic.

In this film, Stuart tells you more about the study: http://youtu.be/NugHfU8Z_NU

and here’s more about Stuart’s research:

www.stuartauld.wordpress.com

@StuAuld

Intecol meeting almost upon us! Remember, the Nordic Society is doing what I hope will be a very exciting session on biodiversity. This was a joint effort by Ecography & Oikos. I just completed preparing my talk.  Here it is as a little teaser!  I may also do a short video of it to practice.  Any other speakers game, post your talks too!

http://bit.ly/lortie-intecol2013

What can we learn from the Jurassic when it comes to modern Climate changes? read more in the Early View paper in Oikos Learning from the past: functional ecology of marine benthos during 8 million years of aperiodic hypoxia, lessons from the Late Jurassic by Bryony Caswell and Chris Frid.

Below is Bryony’s background story and summary:

“A few years ago whilst on a field trip Chris and I began discussing the ideas that form the basis for this paper.  To him Jurassic marine systems initially appeared to be very different from those we see today being dominated by exotic large marine reptiles, ammonites, belemnites and fish.  The seafloor however was more familiar in its composition of clams, snails, echinoids and so on.  Modern marine systems depend upon key functions delivered by sea-floor communities such as these.  The ecological functions support and regulate multiple processes in the marine ecosystem such as the regeneration of nutrients, absorption and treatment of wastes, and the provision of food. Our discussions led us to ask how will the functioning of marine systems respond to the rapidly expanding footprint of human pressures, such as climatic change and nutrient runoff, in the longer term? The effects that these pressures exert on the seafloor, and the wider marine system, are not unique to modern marine systems. The Mesozoic oceans suffered from similar, albeit natural, pressures the effects of which manifest as remarkably similar patterns of change.  This observation inspired us to explore the potential changes in the delivery of key ecological processes within the Late Jurassic oceans (~150 million years ago) as an analogue for the changes that we see today.

Our study is the first to quantify changes in ecological functioning of the ancient seafloor. The data we use comes from the Late Jurassic and covers ~8 million years of fluctuating regional ocean de-oxygenation, and with it we investigate changes in the biological attributes that supported the palaeoecological functioning in the Wessex Basin, Dorset, UK. The fossilised remains of the Late Jurassic seafloor contain gastropods, brachiopods, scaphopods, bryozoans, echinoids, serpulids, hydroids and crustaceans, but it was dominated by bivalve molluscs.

In the oceans today we are witnessing the rapid expansion of areas of low dissolved oxygen that is caused by a combination of warming and elevated nutrient/organic enrichment of the oceans. The Jurassic was a period of ‘greenhouse’ conditions and de-oxygenation was common in its shallow continental seas within restricted basins such as the Wessex Basin. The results of our analyses show that the species composition of the Late Jurassic seafloor communities changed in the face of the environmental stress caused by the decreased oxygen levels, but that ecological functioning was initially maintained – lowered oxygen levels did not trigger a switch to a seafloor ecosystem that worked in a fundamentally different way. However, as oxygen levels continued to decrease the system underwent a marked change in the way it functioned. We have been able to identify this threshold relative to geochemical proxies for environmental change.

The results of our study suggest that we may be able to identify the thresholds that will trigger this change in modern systems.  The modern seas and oceans support multiple ecosystem services and the collapse of ecological functioning has serious implications for coastal economies. Collapse of functioning is therefore a state that environmental managers should seek to avoid. The ecological changes we observe in the Jurassic are consistent with the patterns emerging from studies of modern systems. Functional collapse occurs rapidly once critical thresholds are exceeded and recovery from this often takes decades and follows a unique and unpredictable return path.

The cliffs near Kimmeridge showing clear metre scale alternation between organic-poor and organic-rich layers.  These variations reflect changes in oxygen levels at the seafloor during the Late Jurassic. 

Exploring the Jurassic seafloor as it is exposed, in the Kimmeridge Clay Formation, today on the foreshore.

A fossil rich bedding plane representing one of the hypoxic palaeocommunities (E2c).  It contains several of the dominant bivalve species (Protocardia morinica, Palaeonucula menkii, and Isocyprina spp.) and the limpet Pseudorhytidopilus latissima.”

 

 

Climate change and plant movements and invasions was discussed during the ESA-meeting 2011. The result – a Forum paper is now published online in Oikos: “Movement, impacts and management of plant distributions in response to climate change: insights from invasions” by P. Caplat et al. Below you find Yvonne Buckley’s background story to the paper:

Plants are moving as their habitat changes due to climate change. If species are to persist they are required to adapt or move somewhere else. Species dynamics are extremely hard to predict, making global change research a challenging enterprise. Invasion ecology however has many case-studies, concepts and challenges in documenting, predicting and managing how species move, and how their movement affects ecosystems.

Invasive plants are extremely good at moving and present very real challenges for predicting where they will move to, how fast and how ecosystems will respond to immigrants. We invited 10 colleagues from around the world with diverse interests in the ecological, evolutionary and social dimensions of invasion to discuss how invasion ecology can contribute to predictions of plant movement in response to climate change at a special session of the 2011 Ecological Society of America meeting in Austin. Sparked by presentations and discussion at that session we wrote a discussion piece for the Oikos Forum.

Climate change and biological invasions exhibit similar dynamics and processes. In the following figure, we show A: a New-Zealand native tree (Nothofagus menziesii), recruiting above the climatic tree line in the Mataketake Range, New-Zealand (courtesy of M. Harsch); B: an invasive pine (Pinus nigra) expanding on a mountainous grassland near Lake Coleridge, New-Zealand.

In the paper, we outline the similarities between invasion dynamics and climate induced range-shifts. The figure below shows how concepts from invasion biology can contribute to questions relevant to climate change research.

Many of these concepts concern the properties plants should have to be able to track their environment or adapt to new conditions. The colonisation of new environments emphasizes the role of dispersal, which has been intensely studied in invasion biology. The following picture illustrates this. A: Invasive thistle Carduus nutans responded to experimental warming by growing taller, therefore increasing its dispersal ability; B: having light, winged seeds allows pine tree Pinus nigra to spread far and fast; C: the dispersal traits of invasive Crepis sancta evolved rapidly when the plants colonized a fragmented urban environment (courtesy of G. Przetak); D: high seed production , amongst other traits, allow Acacia pycnantha to invade grasslands in the Western Cape, South Africa.

Invasion processes are not entirely analogous with plant movements in response to climate change but they do present some useful examples and a large volume of data which could be synthesised to shed light on ecological, evolutionary and social processes that are involved when plants move.

Many animal species show seasonal switches in their habitat use. For example, animals may move between aquatic and terrestrial habitats, flowing and still waters, coastal areas and open seas, or forest floors and canopies. How do animals decide which habitat to use? One way to understand animal habitat selection is to focus on the energetic gains and costs associated with foraging in each habitat. This has been the basis of much ‘optimal foraging’ research over the past few decades. Foraging models, which calculate the net energy intake per unit time (‘profitability’) available to the animal while foraging in different habitats, can yield a process-based understanding of why animals switch habitats.

In our paper ‘Go with the flow: water velocity regulates herbivore foraging decisions in river catchments’ , now published Eary View, we used a combination of observational, experimental and modelling work to understand why flocks of non-breeding mute swans (Cygnus olor) show a seasonal switch in habitat use in shallow river catchments. From our previous work, we knew that swans switch from feeding on grasses in pasture grass fields, to feeding on aquatic plants in the river itself, between April and May each year. Due to their high food requirement (up to 4 kg of fresh vegetation per day), lack of predators and high tolerance to disturbance, non-breeding swans are ideal for studies of the influence of foraging profitability on habitat selection. Hence we suspected that the habitat shift would be linked to seasonal changes in one or more of three parameters: food quantity, food quality, and metabolic foraging cost.

 

A flock of mute swans feeding on submerged plants in a shallow rive

 

We combined field and literature data with an optimal foraging model to investigate the observed seasonal habitat shift by mute swans. Our study system for this investigation was the River Frome in southern England, which has a population of approximately 300 swans. We measured the quantity and quality of the two food resources available to swans, aquatic plants and pasture grass. We took quantitative plant samples each month from 18 paired river and field sites within the catchment to measure how the biomass of each food resource changed over the study period. The energy content of plant and swan faeces samples from four of these sites were determined using bomb calorimetry, which showed that the food quality was relatively constant over the study period. We estimated the intake rates for aquatic plants by conducting feeding experiments on captive swans, and for pasture grass by allometric scaling of published data. We used published literature and calculated water velocities to estimate foraging costs. Whilst foraging costs of pasture grass feeding were stable over time, river feeding became more efficient as water velocities declined between spring and summer; slower water meant less energy had to be expended swimming.

 

The lead author with a tray of swan faeces for energy analysis, illustrating the less glamorous side of working with large, charismatic vertebrates

 

The lead author delivers part of the ad libitum supply of aquatic plants to a captive swan at the start of the functional response experiments

 

Finally, we used an optimal foraging model to predict the average net rate of energy gain in each habitat, for each month between March and September. The model could have either fixed values (i.e. average values for the study period) or variable values (i.e. monthly values) for the key parameters, to allow us to assess the effects of seasonal changes on profitability and habitat use. We compared the predicted ‘best’ habitat for each month with the observed field data on habitat use. By sequentially testing alternative models with fixed or variable values for food quantity, food quality and foraging cost, we found that we needed to include seasonal variance in foraging costs in the model to accurately predict the observed habitat switch date (i.e. April to May). However, we did not need to include seasonal variance in food quantity and food quality, as accurate predictions could be obtained with fixed values for these two parameters. Therefore, our model indicated that the seasonal decrease in aquatic foraging costs was the key factor influencing the decision to switch from pasture to river feeding habitats. Many previous studies have ignored the role of seasonal changes in foraging costs in driving switches between habitats. Our study offers a mechanistic understanding, based on the gains and costs associated with different food resources, of the observed shifts of a generalist herbivore between alternative habitats.

Understanding the factors which determine habitat selection are necessary to explain the patterns of animal distributions that we observe in nature. Furthermore, we aim to use our understanding of swan habitat selection to inform ecosystem management. Where they feed in shallow rivers, flocks of mute swans may damage the plant community and threaten conservation objectives. Herbivore damage to valuable plant communities is a problem seen around the world, for example deer in temperate woodlands and geese in agricultural crops. Where we understand the factors which determine herbivore habitat use, we may be able to manipulate these factors to shift herbivores away from the threatened habitat. Whether or not we can successfully use our understanding of the rules of habitat selection to devise practical habitat management schemes to prevent overgrazing, it certainly provides an interesting applied focus for future research in this area of ecology.

Kevin A. Wood

Do bold individuals have higher metabolic rates? Find out in the new Early View paper “Personality and basal metabolic rate in a wild bird population” by Sandra Bouwhuis and co-workers. Here’s Sandra’s short summary of the study:

Like humans, individuals of many species are found to vary in their personality type. Some individuals are bold and eager to explore new environments, while other individuals are shy and more cautious. Such personality variation has been suggested to be related to general lifestyle differences between individuals, such that bold individuals opt for a ‘live fast, die young ‘ lifestyle, while shy individuals invest in survival and the future. On the physiological level, such individual differences have been proposed to be supported by different metabolic machinery and, as a result, different metabolic rates. This latter theory was tested in a wild population of great tits, living in Wytham Woods in the UK, over three years. Contrary to the expectation, among 700 individual birds no strong relationship between metabolic rate and personality was found. Instead, the results of the study suggest that individual metabolic strategies may be highly variable and that such metabolic strategies, instead of an average metabolic rate, may be related to personality variation.

How can we provide the best circumstances for our kids? The new Oikos Early View paper “Adaptive transgenerational plasticity in the perennial Plantago lanceolata” , by Vit Latzel and co-workers, deals with this issue – in plants. Read Vit’s story here:

Imagine that you have to live your whole long life in one spot and that your kids, for whom you cannot even choose the father, will then live very close to you without the possibility of them finding a better environment. How can you best provide for them and make their lives at least slightly easier? This is exactly the challenge that many cross-pollinated long-lived plants must face. Luckily for some mothers, it seems that they can prepare offspring for the environment that they will be facing – giving them an advantage over unprepared competitors. They could do this through the mechanism known as adaptive maternal effects or adaptive transgenerational plasticity. However, rigorous demonstrations of this have been surprisingly rare, probably because appropriate experiments are difficult to conduct and/or the wrong traits have been measured. We did a straightforward experiment on the common perennial Plantago lanceolata (ribwort plantain), testing whether offspring grown in the same level of nutrient availability as their mothers were more successful than offspring grown in a non-maternal environment. Unlike other studies, we considered total carbon storage in roots as the measure of offspring success, because, in contrast to fitness estimates based on single-year fecundity, storage amounts accurately indicate long-term success of polycarpic perennials across several seasons. We found that offspring took an advantage of maternal environmental nutrient levels where they accumulated significantly more carbohydrates than those grown in non-maternal environments. This adaptive transgenerational plasticity was consistent across maternal genotypes and was not affected by climatic fluctuations during offspring development. Our work suggests that adaptive transgenerational plasticity is common in Plantago lanceolata. We also believe that if appropriate estimates of plants success are considered, similar transgenerational adaptive plasticity can likely be found in many other perennial species, and that transgenerational modification of storage dynamics in perennial plants can contribute to their ecological variation.

Ribwort plantain in a natural population and in our cultivation. Graph shows the higher level of carbon storage in offspring grown in maternal than in non-maternal nutrient environment.

Are you scared of the dark? Predators can change the species present in a community by consuming particular individuals removing them from the ecosystem. However, a new paper published Early View in Oikos “Fear in the dark? Community-level effects of non-lethal predators change with light regime”, Coreen Forbes and Edd Hammill” shows that under dark conditions, fear of predation alone is enough to lose species from communities. Under dark conditions, photosynthesis is impossible meaning the only species that can survive are ones that can collect energy from existing sources. Moving around to collect this energy also increases the chances of encountering a predator, so when scared, some species reduce the rate at which they move around. This reduction in movement means other species can harvest the energy source faster than the “scared” species. Because the scared species is now less competitive, it can be driven to extinction despite the fact it is not being eaten by predators. Our research shows how important predators are for keeping ecological communities in order

Welcome to the Oikos Editorial Board, Dr. Isabel Smallegange, University of Oxford, UK. Isabel’s research focuses on unravelling the mechanisms that maintain male polymorphisms, and on understanding and predicting the eco-evolutionary consequences of (human induced) environmental change. In her studies she uses mites as a model system and combines modelling with behavioural and population experiments. More info is found on her website: www.bio-demography.org/isabel.html‎.

Isabel, what’s you main research focus at the moment? 
The focus of my research is to understand how ecology and evolution interact to determine the evolution of traits and the dynamics of populations in response to environmental change. I specifically focus on the evolution of male dimorphism and combine theory with experiments to unravel the links between ecology and evolution.

Can you describe you research career? 
I started out in behavioural ecology as I was (and still am) fascinated by all the different behaviours that animals display. During my PhD at the Netherlands Institute for Sea Research I studied the foraging behaviour of shore crabs. However, by the end of my PhD I wanted to scale up my work to the population level, which was not possible with shore crabs, and therefore I went to the Max Planck Institute for Ornithology to analyse long-term datasets on bird abundances. This first Post Doc was a great learning experience, however, I missed the experimental element to my research and moved to Imperial College London where I set up a laboratory to use mites as a model system to study population dynamics and the evolution of male dimorphism. My lab has now moved to the University of Oxford where I’m continuing my research on eco-evolutionary dynamics.

How come that you became a scientist in ecology? 
I always liked biology and from a young age I was fascinated with animal behaviour. I actually thought I would never be able to get a job in behavioural ecology but, luckily, I did find a PhD position to study animal behaviour. During my PhD I learnt many different skills that set me up for a career in ecology. Although now I’m not studying animal behaviour anymore, I still work with animals on very exciting questions in ecology and evolution.

What do you do when you’re not working? 
At the moment I spend most of my spare time with my 6-month old son who demands a lot of attention!

Selected publication: Smallegange IM, Coulson T. 2013. Towards a general, population-level understanding of eco-evolutionary change. Trends in Ecology and Evolution 28:143-148.

The introduction of non-native plants usually invokes a wave of pessimism among biologists.  Some of these introduced plants can invade natural ecosystems where they can cause tremendous problems.  And to make matters worse, it is very difficult to predict much about the ecological impact of a particular non-native plant prior to its introduction.  We argue that one important consequence of a plant introduction is fairly predictable:  which native herbivores are able to colonize it.

In the Early View Oikos paper “Predicting novel herbivore-plant interactions”, Ian Pearse, David Harris, Richard Karban, and Andrew Sih argue that we can predict which native herbivores will successfully colonize which introduced plants if we understand some of the mechanisms of native herbivore plant interactions and the general properties of native food webs.

The basis for predicting novel associations between herbivores and plants is to define the “match” between an herbivore and its potential hosts.  The logic behind this ends up being analogous to the way the Netflix movie website guessed (perhaps correctly) that I might like to watch “His Girl Friday” next (it is similar to another movie that I watched recently) or maybe an episode of “Downton Abbey” (a show that seems to be popular with many people right now).  Indeed, the attempts to “match” us with a novel product (log in to Amazon) or person (visit match.com) are essentially pervasive to anyone who ventures onto the internet.  This works because internet sites and companies collect a large (creepy?) amount of information about us and the products they sell.

In the context of novel herbivore-plant associations, we already know many of the factors that drive these associations (phylogenetic constraint in host breadth, secondary metabolites, phenology, etc).  And we have even begun to compile information about many native plant-herbivore food webs, which is perhaps akin to Netflix’s list of movies that I and other costumers have watched.  So, this paper suggests that (when armed with accurate native food webs and good lists of plant traits and evolutionary histories) we can start to make more accurate predictions about which native herbivores will colonize which non-native plants.

Of course, the natural history of individual organisms is complicated, and some interactions will be hard to predict.  For example, the interaction between an herbivore and its novel host is an evolving relationship (see a recent Oikos review by Matt Forister dealing with this topic).  But for many cases, herbivore interactions may be one of the most predictable elements of plant introductions.

The Editor’s choice papers in the July issue of Oikos are “A critical analysis of the ubiquity of linear local–regional richness relationships” by Goncalves-Souza et al. and “Bottom–up and top–down forces structuring consumer communities in an experimental grassland” by Rzanny et al.  Both are available free online! Here’s the EiC’s motivation for the choice:

Besides promoting synthesis, Oikos has a tradition in publishing studies that challenge widely accepted ecological paradigms. The ubiquity of linear relationship between local and regional species richness is such an idea that found its way to many textbooks. The potential impact of regional and local processes on community structure has been traditionally tested by regressing local against regional species richness. This approach was justified by the idea that communities controlled by regional processes are unsaturated, while those affected by local processes are not. However, while such a linear relationship has been theoretically criticized, a critical reevaluation has so far not been done. Thiago Gonçalves-Souza and colleagues reanalysed published studies with a new unbiased method and found no prevalence of linear relationships and more than 40% of misclassifications. Its apparent ubiquity appeared to be due to the use of biased statistical methods (linear regressions to detect linearity). The study demonstrated such local-regional diversity relationships to follow other ‘rules’ than linear ones. The metacommunity perspective provides a framework to study the importance of processes acting and interacting at different spatial scales. A full understanding of these mechanisms will ultimately generate synthesis on the form and strength of the local-regional diversity scaling rules.

While this framework likely advances our understanding of the processes leading to species diversity, we still lack proper insights on the relative strength of different local mechanisms (food web interactions for instance) that structure species communities. Species at intermediate trophic levels (consumers) are expected to be affected by the interplay between bottom-up and top-down effects, but synthesis on the relative importance of these effects is lacking. By analysing data from a long-term grassland diversity experiment, Michael Rzanny and colleagues demonstrate bottom–up forces to account for the major part of the explainable variation within the composition of all functional groups of consumers (plant chewers, suckers , saprophages) but also predators and parasitoids. Legumes appeared to be an especially important driver of consumer community structure. Predator-mediated top–down forces also influenced the majority of consumer functional groups, but were much weaker. In order to partition the different sources of variation, redundancy analysis was applied. Equally interesting, and again emphasising the interactive effects between local and regional processes, was the importance of different spatial components for explaining, especially, predator community structure.

The Nordic Society has put together a special symposium for the upcoming Intecol meeting.  We hope to see you all there and that you will find it an interesting set of talks.  It is a double session on Tuesday August 20^th in the morning. The full programme details will be available by the end of July apparently.

Goals of the diversity symposium

The primary objective of this symposium to highlight the breadth of diversity studies, both empirical and theoretical, with an eye to promoting novelty and identifying research gaps for the next 100 years.  Ancillary goals that will be addressed to meet this overarching objective include the following.

(i) To critically examine scale as it relates to understanding ecological and evolutionary processes that shape patterns of diversity.

(ii) To develop a clear set of directions for future studies of diversity that augment species diversity estimates with genetics in spatial landscapes.

(iii) To describe pivotal concepts and relationships that limit our capacity to effectively use and measure diversity and how it has changed and will change in the future and propose solutions.

(iv) To identify the critical species and places that anchor diversity studies and enhance diversity in changing climate.

The line-up of speakers is very extensive, and the second column in each table lists the allotted time.  We designed the first session to cover mover ground quickly and directly and the second session provides a bit more time for their respective topics.

Session 1 chaired by Jens-Christian Svenning

Dr Richard Michalet	The contribution of local-scale facilitative interactions to community diversity and composition	15
Dr Carlos Melian	Connecting diversification and biodiversity dynamics across spatial scales	15
Mr Tadashi Fukami	Spatial scale and the historical contingency in community assembly as a source of beta diversity	15
Dr Brody Sandel	Patterns of diversity across scales: Challenges and opportunities	15
Dr Hanna Tuomisto	A critical look at the diversity of diversity: do we know what we are talking about?	15
Dr Pedro Peres-Neto	Spatial autocorrelation, metacommunities, and null models: the thrills of diversity	15
Dr Franz Uiblein	Widely distributed species versus species complexes in the oceans: where to go towards management of species-rich resources and habitats?	15
Summary by Chair		15

Session 2 chaired Christopher Lortie 

Dr W. Daniel Kissling	Multi-species interactions across trophic levels at macroscales: retrospective and future directions	30
Mr Matthias Schleuning	Integrating functional and interaction diversity into biodiversity-ecosystem function research	30
Dr Lonnie Aarssen	Evolution and the sizes and numbers of species:  unpacking the diversity of vegetation	30
Dr Christian Schöb	Global patterns of β-diversity along alpine gradients point to locally changing drivers of community assembly – but only in the absence of foundation species	15
Dr Christopher Lortie	Diversity versus interactions: are diverse groups more important than large effects?	15

In my recent explorations into synthesis and the role of Oikos and other major drivers of this movement, here are some facts from Web of Knowledge and online search tools.

(1) Close to 20,000 primary research publications discuss/report effect size estimates in ecology.

(2) Approximately 15 times more meta-analyses published in ecological journals relative to systematic reviews.

(3) PLOSONE publishes majority of systematic reviews for most disciplines possibly including evolutionary biology.

(4) Historical signal of narrative reviews persists in modern synthesis.

(5) Citations per item to meta-analyses now trump narrative reviews.

(6) Oikos ranks 5th in publishing meta-analyses.

(7) The benefit to effort for systematic reviews generally higher than meta-analyses*.

*However, see pre-print on this as it does not necessarily mean we should do them instead of meta-analyses as evidence-based transformations are more likely to occur from meta-analyses.

I am experimenting with PeerJ as a new model to get friendly peer-review in advance of submitting to a journal.  Two papers were on my plate – a general synthesis and role of meta-analyses and systematic reviews paper and a more practical paper on how to interpret them. Any feedback appreciated!

Formalized synthesis opportunities for ecology: systematic reviews and meta-analyses. 

Practical interpretation of ecological meta-analyses.

Now online: “Increased temperature alters feeding behavior of a generalist herbivore” by Nathan P. Lemoine and co-workers. Read more about how an  increased temperature may affect plant growth and herbivory:

Temperature plays a crucial role in determining ecological processes. For example, temperature can control rates of predation, herbivory, individual growth rates, population growth rates, and mortality rates, to name a few. Unfortunately, we know little regarding the effects of temperature on herbivore choices. That is, we do not fully understand how temperature influences which foods herbivores choose to eat or which foods provide optimal diets. Herbivore physiology is strongly controlled by environmental temperature (if the herbivore is an ectotherm), as rising temperatures promote growth (to a point) and increase the demand for vital nutrients, like sugars, proteins, nitrogen, or phosphorus. If true, then daily, seasonal, decadal, or climatic fluctuations in temperature should alter the plants that herbivores consume.

We tested the hypothesis that temperature alters herbivore performance (consumption and growth rates) and feeding preferences among plant species using the Japanese beetle, Popillia japonica.

We found that the effects of temperature on P. japonica growth and consumption rates varied widely among plants species: increased temperatures stimulated growth on some plants and decreased growth on others. The differences in growth among plant species are attributable to plant nutritional quality. At low temperatures, plant nutritional content did not affect beetle growth. At high temperatures, beetles grew best on plants with high nitrogen and carbon content, perhaps reflecting increased demand for nitrogen-rich materials or carbohydrates.

Additionally, by extracting plant secondary chemicals, we found that temperature reorganizes beetle feeding preferences by altering the effects of plant chemical defenses. Interestingly, the plants that beetles preferred at high temperatures were not the plants on which beetles grew best, indicating that the beetles were making decisions that may not lead to optimal growth rates.

Our results indicate that direct effects of temperature on herbivore physiology can possibly re-organize the intensity of herbivory among plant species and that these changes can be predicted based on plant nutritional quality. These changes will become more important in the future as the climate warms.

How interference competition affect population dynamics is explored in the new Early View paper in Oikos “Linked exploitation and interference competition drives the variable behavior of a classic predator–prey system” by John P. DeLong and David Vasseur. Here’s John’s background story and summary:

We had a hunch. While trying to understand how interference competition works, we began to suspect that traits that influenced the rate at which consumers encountered their resources would also influence the rate at which consumers encountered each other. Maybe some measure of exploitation competition would therefore be related to a measure of interference competition.

Figure 1. Traits that influence the rate of consumer-resource encounters might also influence the rate of consumer-consumer encounters, generating a link between exploitation and interference competition.

 

To find out, we measured foraging rates in the classic Didinium nasutum – Paramecium aurelia predator-prey system. By measuring foraging rates at different levels of both the predator and the prey, we could fit a functional response to the data and retrieve estimates of parameters that reflect the magnitude of these forms of competition. If there was any variation in those parameters, we would expect it to be correlated.

Figure 2. Here a Didinium nasutum is consuming a Paramecium bursaria.

We created 16 different populations and nudged them in different directions – they received varying amounts of nutrients, varying amounts of prey and predators, and were allowed to grow for different amounts of time. Then we pulled individuals from the populations and conducted the foraging experiments, once for each population separately. Our functional response included the power-law form of interference – mutual interference – and the standard ‘a’ parameter that characterizes exploitation. Across the populations, exploitation was strongly correlated with interference.

Figure 3. Interference competition (which gets more intense as it gets more negative) is strongly and positively related to exploitation competition (a).

 

Turns out we weren’t the first ones to suspect this. In 1954, Park suggested that the two forms of competition might be linked, but since that time research into competition has largely investigated interference separately from exploitation. Keeping them separate is likely to obscure how competition influences ecological and evolutionary dynamics, especially given that interference can have a rather strong impact on foraging rates.

For example, the Didinium – Paramecium is famous for having highly variable dynamics. Usually, dropping a few Didinium into a plate full of Paramecium leads to one cycle of growth followed rapidly by the extinction of both populations. However, slowing everything down can lead to more oscillatory behavior. These variable dynamics are easily explained by the link between exploitation and interference, with low interference and low exploitation leading to oscillatory dynamics, intermediate competition values leading to stabilized dynamics, and higher values of both leading to deterministic extinction.

Figure 4. Predator-prey dynamics, here simulated for Didinium – Paramecium, vary from oscillatory to deterministic extinction due to the correlated nature of the interference and exploitation parameters.

 

We also found a way to modify the mathematical formulation for the ‘a’ parameter that generates the kind of exploitation-interference relationship we observed. This model suggests that the rate of travel of the predator is an important driver of both forms of competition, bringing a measurable trait to bear on this problem.

Michael Scherer-Lorenzen has just joined the Editorial Board of Oikos. Get to know him by reading the presentation below. And welcome to Oikos, Michael!

In my research I aim to mechanistically understand the biotic control of ecological processes and how global change drivers – such as climate change, land use change, nitrogen deposition, or invasive species – are interacting with this control.  Within this field I focus on the functional role of biodiversity for productivity and biogeochemical cycles. I am currently coordinating the EU Framework Programme VII project FunDivEUROPE, which aims to quantify the role of forest biodiversity for ecosystem functioning and the delivery of goods and services in major European forest types.

Weblink:
http://www.geobotanik.uni-freiburg.de/Team-Ordner/mscherer/Michael-Scherer-Lorenzen

1. What’s you main research focus at the moment? 

Does it matter to the way how ecosystems function whether there are only few or many species present? And if so, which are the mechanisms behind such biodiversity effects on ecosystem processes? Do such functional effects of biodiversity change with changing land use intensity or climate?
These kind of questions are at the basis of my group´s current field of research. We are focusing on processes such as productivity or nutrient cycling, with litter decomposition and plant nutrient uptake being key functions. One challenge we are currently dealing with is the quantification of resource use complementarity, which is one main mechanism that could explain positive plant diversity effects on productivity. In terms of study systems, we work in grasslands and forest ecosystems mainly, using both experimental and comparative appraoches.

2. Can you describe you research career? Where, what, when? 

Because there was a strong focus on ecology at the University of Bayreuth, Germany, I went to this little city in northern Bavaria in autumn 1988, to study Biology. I finished my studies with a thesis on land use effects on plant communities in Southern Chile.
In 1995, I begun my PhD within the pan-European BIODEPTH project under the supervision of Detlef Schulze. BIODEPTH was the first biodiversity – ecosystem functioning experiment in Europe at that time and was coordinated by John Lawton. The whole consortium was a real dream-team, and I learned a lot.
After finishing the PhD in 1999, I worked as an assistant to Detlef Schulze in the German Advisory Council on Global Change (“WBGU”), followed by a position as Executive Director of the Institute of Biodiversity Network (ibn). These two jobs offered interesting insights into policy advising and the function of important international treaties, such as the UN Convention on Biological Diversity, CBD.
I went back to science in 2001 as a research scientist at the Max-Planck-Institute for Biogeochemistry in Jena, Germany, where I established a large tree diversity experiment (BIOTREE).
From 2003 to 2009 I was working in the research group of Nina Buchmann at ETH Zurich, Switzerland. Here, I started to use isotopic tracers to quantify resource use complementarity and to study drought effects on alpine grasslands.
Finally, in April 2009, I got the position as a Professor for Geobotany at the University of Freiburg, which enabled me to set up my own research group on functional biodiversity research.

3. How come that you became a scientist in ecology? 

It all begun during field trips with my parents (my father collected beetles), where my fascination for nature was born. In school, I participated in nature conservation actions and research competitions. For example, together with friends, I was mapping amphibians or developped a protection programme for social wasps. So, it was very clear for me that I wanted to study biology after school. And so I went to Bayreuth…see above.

4. What do you do when you’re not working? 

We have two wonderful children, Falk and Alva, who take most of my non-working time, of course. We are often going out into the forest just behind our garden, or take the bicycle, or play football.

Selected publication:
Scherer-Lorenzen, M. (2013). The functional role of biodiversity in the context of global change. In: D. Burslem, D. Coomes, & W. Simonson (Eds.), Forests and Global Change. Cambridge: Cambridge University Press. In press.

 “In discussing the peculiar type of refraction which occurs when light from the sky enters the surface of still water, it seems of interest to ascertain how the external world appears to the fish.” With these words renowned physicist R.W. Wood, Professor of Experimental Physics at Johns Hopkins University and proud owner of one of the firsthome aquariums, started his 1906 article “Fish-Eye Views and Vision Underwater“. The article was set to offer a scientifically based description of how a fish might view the world outside his glass tank.

Even with all his intellectual curiosity and intuitiveness, Prof. Wood probably could not have imagined that decades later a modern descendant of the water camera he had once designed would be balanced on tripods in forests around the world. Nor could he have envisioned that it would soon become the standard field instrument for characterization of canopy structure and light regimes of forest ecosystems.

But let’s take a step back to understand how the fish got to view the forest.

The phenomenon Prof. Wood exploited in his experiment is governed by Snell’s law. Dating back to the 17th century, Snell’s law also known as Snell’s window is a phenomenon by which an observer looking up from beneath the water sees a perfectly circular image of the entire above-water hemisphere—from horizon to horizon. This is caused by refraction, light bending as it travels from one medium (air) to another (water). As argued by Prof. Wood, the cone of light entering the fish’s eye has an aperture of about 96°, but the rays within it came originally from a cone of 180°. This is the same phenomenon by which a fisheye lens (or hemispherical lens) is able to reach far to the sides of a scene and pull in the visual information of the entire hemisphere onto a plane.

The first practicable methods of hemispherical photographs were developed in 1924 shortly after Dr. R. Hill developed the first fisheye camera for cloud survey records and formation studies. During mid the 50s two ecologists, G.C. Evans and D.E. Coombe from the Botany School of the University of Cambridge, learned that one of these ingenious fisheye cameras had survived the war. Shortly after, they were standing under the dense shade of a small tree of Napoleona vogelii situated in Oil Palm bush near Ibadan, Nigeria. Of course – taking hemispherical photographs.

In 2007 another camera equipped with a fisheye lens was pointing upward to the sky in the canopy of yet another tropical forest, this time in Taita Hills South-East Kenya, where Alemu Gonsamo and colleagues from the University of Helsinki were conducting an extensive measurement campaign for the remnant cloud forest fragments.  Gonsamo and colleagues did not have to face many of the technological shortcomings Evans and Coombe were confronted with just half a century earlier. At that time hemispherical photograph analysis required tedious manual overlaying of sky quadrants and superimposing the track of the sun. With the advent of personal computers and with the replacement of film cameras by digital cameras, researchers are now able to develop digital analysis techniques (link here) and today various commercial and non-commercial software programs have become available for rapid hemispherical photograph processing and analysis. Yet many fundamental issues remain to be resolved.

The resulting hemispherical photographs serve as a permanent record of the canopy geometry, which can be precisely used to characterize canopy structure and light regimes. Canopy structural parameters are critical to adequately represent vegetated ecosystems for purposes ranging from primary productivity, climate change studies, water and carbon exchanges, and radiation extinction. However, as observed by Gonsamo and co-authors, standardization in the definitions of the fractional canopy cover and openness parameters has fallen short, leading to confusion of terms and concepts even in standard text books, making the comparison of historic measures futile.

In the Oikos Early View paper “Measuring fractional forest canopy element cover and openness–definitions and methodologies revisited” Alemu Gonsamo and colleagues take an exciting tour, reviewing concepts, polishing up definitions, and presenting new methodologies to obtain large scale fractional canopy element cover and openness measures using photographs with a fisheye view perspective. Finally, in their Oikos paper, Gonsamo and colleagues argue that hemispherical photography is less time, labour and resource intensive, as compared to the traditional point based measuring techniques of canopy element cover and openness. This included measurements in topographically complex terrains.

Oikos’ Editor-in-Chief, Prof. Dries Bonte, explains his choice of EC-papers for the June issue:

Editor’s choice papers from the June issue create synthesis on invasions.

Zenni & Nuñez  focus in a forum paper “The elephant in the room: the role of failed invasions in understanding invasion biology” on the importance of failed invasions to understand mechanisms behind invasions. They provide a review on studies documenting success and especially failures of invasions and found –not surprisingly I have to say- that only few studies have documented conclusively why populations fail to invade. The authors followed a paired approach contrasting environmental factors in invasive versus non-invasive populations of different species. They were, despite the lack of a well-developed research framework, able to demonstrate that different mechanisms may be causing failures vs. successes: propagule pressure, abiotic resistance, biotic resistance, genetic constraints and mutualist release. Rafael and Martin discuss the evidence available for the factors associated with these failures to invade. They additionally identify research field that are likely to produce misleading insights when neglecting these mechanisms of failure. Such biased reporting may thus not only mislead researchers, but certainly managers on the mechanisms leading to invasions.

There is consensus that when introduced organisms invade, they may cause considerable changes in community and ecosystem dynamics. While invasions are generally associated with negative impacts, Paul Gribben and colleagues demonstrate in their paper “Positive versus negative effects of an invasive ecosystem engineer on different components of a marine ecosystem” that an invasive engineer species may also contribute positively to marine community structure. They more specifically studied the impact of the invasive green alga Caulerpa taxifolia in southeastern Australia on the composition and abundance of the epifaunal and infauna community. More detailed species responses where experimentally approached. While contrasting impacts on different community components were obvious, they also showed that community change following the invasive species’ removal appeared strongly density dependent with the degree of recovery five months post removal related to the initial biomass. Areas with different biomasses of habitat-forming (invasive) species may subsequently have different temporal recovery trajectories. So, as highlighted by Zenni & Nuñez, the impact of the invasive species is strongly context-dependent and its impact differs according to the community components under study.

We’re very happy to welcome Anna-Liisa Laine, University of Helsinki, Finland, to our Editorial Board!

Read more about her below and visit her website http://www.helsinki.fi/~allaine/

What’s you main research focus at the moment?
Much of my research is focused on understanding why pathogens occur where they do. To get at this seemingly simple question I combine
experimental and molecular studies of host-pathogen co-evolution with data on epidemiology. I’m especially interested in how variation is generated in host resistance and pathogen infectivity, and how this variation affects epidemiological dynamics. While I mainly study within season disease transmission, I’m also extremely interested in how parasites transmit from one season to the next.
At heart I’m an ecologist and we do our field work in the Åland archipelago where 4000 meadows are annually surveyed for fungal pathogens of plants.

Can you describe you research career?
After completing my Masters at the University of Oulu in 2001, I started a PhD in the Metapopulation Research group at the University of
Helsinki, under the supervision of Ilkka Hanski. In my PhD I focused on understanding how host-parasite coevolution proceeds in a situation where the hostpopulations are highly fragmented. I defended my theses in 2005 and in 2006-07 in did a post doctoral project in the lab of John Thompson at the University of California, Santa Cruz. There we focused on understanding how plant-pollinator mutualism responds to changes in the local Community composition. I had another post doctoral stint in 2009-10 in with Pete Thrall and Jeremy Burdon at CSIRO, Canberra, Australia. There I had the opportunity to work with the classic wild flax-rust pathogen interaction,
addressing questions of host-parasite coevolution. Now I’m back at the University of Helsinki where I started my own lab in in 2010, and I
work as an Academy research fellow.

How come that you became a scientist in ecology?
When I was a high school student, I loved cell biology, and coming from a family of scientist going into seemed like an obvious choice.  However, when I started my studies at the university, I became fascinated with ecology. This was mainly due to two professors in those early years, Lauri Oksanen and Juha Tuomi. I had the chance to work as a research assistant in Lauri’s herbivory project and my interest for species interactions has continued ever since.

What do you do when you’re not working?
With two small kids, I’ve spent a fair amount of time playing with legos and finger painting recently… When I have a chance, I go
running.

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I protect you and you feed me, says the ant to the plant…read more about ecological networks in the new Early View paper “Spatial structure of ant–plant mutualistic networks” by Wesley Dattilo and coworkers.

In tropical environments, ant diversity is extremely high, reaching approximately 500 species at local scales. Because of both their abundance and diversity, it is extremely common to see ants foraging on plants. Within a spatial environment with a remarkable diversity (eg. Amazon rainforest) different plant and ant species can interact with each other and generate complex ecological networks of interactions. In this study, we studied how ants and plants with extrafloral nectaries interact over space, and we show that although the ant and plant composition of networks changed over space, the highly connected plants and ant species, and the structure of networks remained unaltered on a geographic distance of up to 5,099 m in the southern Brazilian Amazon. These finding indicate that different populations of plants and ants can interact in the same way independently of variation in local and landscape environmental factors. Therefore, our study contributes to understanding of the maintenance of biodiversity and coevolutionary processes in ecological networks.

Ants collecting extrafloral nectar on a plant in the fieldwork.

Wesley Dáttilo collecting ant-plant interactions in the southern Brazilian Amazon

We also welcome Dr. Sa Xiao, Associate Professor at School of Life Sciences, Lanzhou University China. Learn more about him below and on his website

What’s you main research focus at the moment?

My research interests mainly focus on the theoretical ecology and plant ecology. I am particularly interested in the areas of competition and facilitation, species coexistence and diversity, community structure and function. I use computer simulation model as the main research tool, especially the individual-based model programmed with multi-agent modeling language Netlogo. My current researches investigate the relative contributions of neutral theory’s process and niche theory’s process in explaining the multiple empirical patterns at the community-level, such as diversity-productivity relationship.

Can you describe you research career?

I took my PhD at School of Life Science here at Lanzhou University in 2006, where I have been Assistant and Associate Professor since then. In 2009-2011, I did a post-doc in Richard Malet’s lab nin Bordeaux, France. And I have been a Visiting Professor  in Ragan Callaway’s at University of Montana lab during 2010.

 How come that you became a scientist in ecology?

When I was in high school, I had a naïve belief that “Darwin’s theory solved the problems of living nature, and Marx’s theory solved the problems of human society, whereas how to solve the problems between human and nature? This should be the responsibility of ecologist”. So I decided to choose ecology as my life-time career.

 What do you do when you’re not working?

I like cooking very much and I’m particularly well versed in cooking Chinese food. I have strong interest in traditional Chinese philosophy such as Confucianism, Taoism, Yi- ology and Zen. I also like pop music, table tennis and swimming.

And a selected paper:

Xiao, S., Callaway, R.M., Newcombe, G. and Aschehoug E.T. (2012) Models of experimental competitive intensities predict home and away differences in invasive impact and the effects of an endophytic mutualist. The American Naturalist 180, 707-718.

We’re very happy to welcome Dr. Mei Sun, School of Biological Sciences, University of Hongkong to our editorial team!

Get to know Mei Sun here:

What is your research interest?

My main research focus at the moment is on plant speciation mechanisms and biological or other features that facilitate the rate of evolutionary diversification of angiosperms, especially in the family Orchidaceae as well as the Rhizophoraceae.

 

Can you describe your research career?

I became interested in plant ecology when I was an undergraduate working on a final-year thesis project in the field. During my postgraduate studies at the University of British Columbia, I become more interested in plant evolutionary biology. My Ph.D. research was on evolutionary genetics of Hawaii endemic species of Bidens (Asteraceae), a morphologically and ecologically diverse group arising from a single long-distance dispersal event followed by adaptive radiation into a variety of habitats on the Hawaiian Islands.

What made you become a scientist in ecology?

I am a molecular ecologist in the broad sense. Using various molecular marker systems, We aim to address various evolutionary questions, such as the investigations of genetic structure and outcrossing rates of hermaphrodites in natural populations of Bidens to determine whether inbreeding depression is one of the major factors in the evolution and maintenance of gynodioecy (e.g., Sun & Ganders 1986 Evolution); genetic diversity and evolutionary origin of Spiranthes orchids in Hong Kong (e.g., Sun 1996,1997 American Journal of Botany; Sun 1996 Conservation Biology); genetic resources and crop evolution (e.g., Amaranthus, sweetpotato, and rice); natural hybridization and phylogeography of Rhizophoraceae. More recently, I am also interested in comparative genetic analysis to understand the evolution of invasiveness in plants that are exchanged between SE Asia and Americas.

What do you do when you’re not working?

Reading about any subject that catches my attention at the moment; listening to soundscape music; watching TV; and doing Yoga …

For a recent representative publication:  please see

Mei Sun, Eugenia Y. Y. Lo   2011

Genomic Markers Reveal Introgressive Hybridization in the Indo-West Pacific Mangroves: A Case Study.

Research Article | published 11 May 2011 | PLOS ONE 10.1371/journal.pone.0019671

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0019671

Mei Sun’s webpage

What should be included in the term “Invasive species”? In the new Early View Forum paper “Another call for the end of invasion biology”, Loic Valery discusses the issue. Here is a short summary of the paper:

The bulk of the literature devoted to biological invasions ignores native species and restricts the field of study to only introduced species. This split used by many researchers to justify the emergence of a distinct discipline is increasingly openly challenged.

Based on the etymology of the word “phenomenon” (i.e. what is seen, what is perceived by the senses), we show that a biological invasion manifests itself, always and only, by the rapid appearance of a state of dominance of a species. Therefore, there is no reason to take into consideration other factors (in particular, the biogeographical origin of the invader) that prove to be both inappropriate and inoperative from a theoretical and practical viewpoint, respectively.

Thereby removing any justification for the autonomy of invasion biology, we advocate a more integrated study of all species on the move.

Invasive species can also be native. Here are two examples of native invaders in Europe:  the sea couch grass Elymus athericus Link spreads in salt marshes, from high marsh towards middle and low parts where it forms large dense monospecific stands (here, in the Mont-Saint-Michel bay); and  the wild boar Sus scrofa L., whose populations have exploded demographically in forests and agricultural systems, now extends in big cities such as Berlin, Milan or Barcelona for foraging. (Photographs: courtesy of André Mauxion).

Size is not all! Even small herbivores have effect on plant community, as shown in Salvador Rebollo and co-workers new Early View paper shows: “Disproportionate effects of non-colonial small herbivores on structure and diversity of grassland dominated by large herbivores”.

Here is a summary of the study by Rebollo:

Grasslands are grazed by a complex assemblage of herbivores that differ in body size, abundance, diet, and foraging strategies.  Grazing studies have most often examined effects of large herbivores, probably due to their greater amounts of plant consumption and economic importance.  Studies of small herbivores have focused on social, central-place foragers that reach high local densities and build conspicuous burrow systems, such as prairie dogs or European rabbits.  The role of more evenly dispersed small herbivores in structuring vegetation, especially in perennial grasslands, has been less studied.  What is the importance of these cryptic small herbivores?

Our research was conducted in the semiarid shortgrass steppe of the North American Great Plains, a grassland with a long evolutionary history of grazing by large generalist herbivores and one of the most tolerant ecosystems to grazing by these herbivores.  This ecosystem is considered marginal habitat for small herbivores (except for the social and colonial prairie dogs) due to the lack of overhead cover, the low seed-to-vegetation production ratios, and small seeds of the dominant plant species.  Peak biomass and consumption of rodents and rabbits was estimated to be a fraction (<8%) of that of large herbivores.  We hypothesized that 1) large generalist herbivores would affect more abundant plant species and proportions of litter (old fallen vegetation), bare ground, and vegetation cover through non-selective herbivory, and 2) small herbivores would affect cover and richness of less abundant species, through selective but limited consumption.

Vegetation in one of the large-plus-small herbivore exclosures. Exclusion of herbivores of both body sizes had complementary and additive effects that were linked to increased abundance of tall and decreased abundance of short plant species. Uncommon species as a group were not affected by the additional exclusion of small herbivores, but the tall annual Tragopodium dubious (compositae plant located in the front part of the photo), was an example of one uncommon species that did increase with small herbivore exclusion.

David Augustine conducts a prescribed burn in shortgrass steppe at the Central Plains Experimental Range.

The study site was at the Central Plains Experimental Range (CPER) in northeastern Colorado, USA, one of the Long Term Ecological Research (LTER) grassland sites (Photos 1 and 2), as well as a Long-Term Agro-ecosystem Research (LTAR) network site.  We found that the exclusion of large herbivores affected litter and bare ground, and basal cover of abundant, common, and uncommon species.  Contrary to our hypothesis, additional exclusion of small herbivores did not affect uncommon components of the plant community, but had indirect effects on abundant species, decreased the cover of the dominant grass Bouteloua gracilis (blue grama) and total vegetation, and increased litter and species diversity.

Paul Stapp handles a thirteen-lined ground squirrel, one of the most common small mammal species in shortgrass steppe at the Central Plains Experimental Range.

Our findings show that small mammalian herbivores had disproportionately large effects on plant communities relative to their small consumption of biomass.  Grazing by the combination of large and small herbivores favored recovery of short grasses after extreme droughts, providing resilience to the shortgrass steppe and contributing to the long-term maintenance of vegetation basal cover.  Our study expands prior work about small herbivores and demonstrates that even in small-seeded perennial grasslands with a long history of intensive grazing by large herbivores, non-colonial small mammalian herbivores should be recognized as an important driver of grassland structure and diversity.  Therefore, the importance of small herbivores was greater than initially thought and their effects on plant communities, isolated or in interaction with large herbivores, should be part of an integrated theory of how about herbivores influence grassland diversity.

Justin Derner sorts yearling steers for grazing experiments (and provides comedy relief) at the Central Plains Experimental Range.

 

In the new Early View paper “Trait-mediated indirect interactions in a marine intertidal system as quantified by functional responses”, Mhairi E. Alexander and co-workers, have studied how factors as habitat compelxity affect predators and how the predators effect prey populations. Here’s their own summary:

It is well known that predation is important in community structure and functioning. It is also understood that the impact of a predator can be influenced by a number of biotic and abiotic factors. For example, the presence of higher-order predators can influence behaviours of intermediate species that can affect their consumption of prey through trait-mediated effects. Habitat complexity can also be an important mediating influence that in turn can influence the numbers of prey that are consumed. What is less well understood however is how these factors interact and contribute to prey population stability. In this study we address this by detecting and quantifying such trait-mediated indirect interactions (TMIIs) using functional responses, which consider a predator’s consumption over a range of prey densities, to investigate the implications for prey population regulation and stability,

We conducted several experiments to investigate how the influence of a higher-order fish predator combined with habitat complexity affects the behaviour of an intermediate amphipod predator from marine intertidal habitats. We first tested whether amphipods were able to determine higher-order predator presence. We found that amphipods demonstrated anti-predatory behaviour via a reduction in activity with the addition of cue that was seawater mixed with crushed conspecifics as well as seawater from tanks holding fish fed conspecifics and also those fed bloodworm. Interestingly, there was no reaction to fish fed an algal diet or those that had been starved. As we didn’t find any response of the basal prey, a commonly occurring isopod, to these cues, we went on to investigate how the presence of the cue in combination with habitat complexity affected the amphipods predation rates and whether the observed reduced activity translated into reduced foraging.

We observed that when there was no habitat or fish cue, amphipods showed what are considered to be potentially destabilising predatory responses towards the isopod prey. With the addition of habitat, however, the response was found to become stabilising as a result of a reduction in consumption of prey at low densities.  When habitat complexity was not included, the presence of fish cue was found to reduce the magnitude of the predator’s consumption of prey at higher densities, as would be expected with reduced activity in the presence of a predator. However when habitat was present in combination with fish cue, although reduced consumption occurred at low densities, at high prey densities it was increased in comparison to predation with habitat complexity and no cue. This seemed to occur as the fish cues drove the amphipods into habitat with more prey and thus actually enhanced predation of the basal prey.

The results from this study demonstrate the utility of functional responses in addressing questions of prey population stability. In addition we have further highlighted how complex predator-prey interactions can be, as well as exploring the relevance of environmental and biological cues that can result in unexpected and complex outcomes.

Oikos will publish synthetic meta-analyses open access and with high priority, and has assigned Christopher Lortie as deputee editor responsible for handling and inviting such contributions.  Jodi Price and Meelis Partel used meta-analyses to examine experimental evidence that functional similarity between invaders and resident communities reduces invasion. They found evidence for forb species but not for grasses, but equally important, their study highlights the fact that such patterns are more prominent in artificially assembled communities than in more natural communities with species or functional groups removed. Only by synthesing data from multiple studies the authors can unambiguously demonstrate that ecological mechanisms that are both theoretically and empirically underpinned may be only limited expressed under natural settings.

As a second editor’s choice we selected a theoretical study by Sonia Kefi and co-authors exploring to which degree critical slowing down is a key phenomenon to measure the distance to a tipping point in ecosystems. Tipping points are abrupt, unexpected and irreversible shifts within ecosystem. Specific ecosystem characteristics like spatiotemporal changes in biomass or population sizes may provide hints or early warning signals about an approaching shift. There is indeed a quickly expanding literature suggesting the presence of such early warning signals. By using analytical modelling, the authors demonstrate that -contrary to the ruling perspective- early warning signals based on critical slowing down are representative for a broader class of situations where systems experience increasingly sensitivity to perturbation. They are hence not solely specific to catastrophic shifts. This study consequently warns for a careful interpretation of critical slowing down as an early warning signal. It thereby stimulates further research aiming at developing and interpreting alike indicators to catastrophic ecosystem shifts whose occurrence may be extremely important for the livelihood of people living in such threatened ecosystems.

Editor’s Choice papers are freely accessible online for three months.

One of the most cited papers in Oikos, during 2011 (published 2009 and 2010) is “Life history tradeoffs influence mortality associated with the amphibian pathogen Batrachochytrium dendrobatidis”  Trenton W.J. Garner and co-workers. Here, Trent gives a short summary about the paper and tries to explain why it has been so important.

The chytridiomycete fungus Batrachochytrium dendrobatidis is a potentially lethal parasite of amphibians considered by many to be a primary factor behind global amphibian declines. It’s been associated with mass mortality and amphibian species decline on four continents and is the subject of a heck of a lot of research effort. However, at the time of the work, almost no published studies had attempted to test hypotheses developed from field observations of infection and mortality, and none had done so using both robust experimental design and multiple life history stages. The study was a real team effort, incorporating the results of extensive field work, multiple experiments and a concerted effort to isolate the parasite from field mortalities. While the results of experiments broadly supported the conclusions derived from field data (infection and death are predominantly related and Batrachochytrium dendrobatidis is likely the cause of post-metamorphic mass mortality events of common toads Bufo bufo in Spain), some previously unconsidered dynamics were revealed. We found that increased mortality was associated with weaker doses of the fungus, but often when infection did not appear to have occurred. We have since shown this to be the case in another amphibian species (Luquet et al 2012 Evolution).

Exactly how the risk of mortality can increase without detectable infection at time of death remains uncertain, but this is certainly different from what is seen in highly susceptible host species, where the burden of infection correlates positively with increased risk of death. As well in our study decoupling of infection from mortality was only detected in larvae. Previous to this, the tadpole stage was primarily overlooked as a stage susceptible to any substantial costs imposed by chytridiomycosis. This is because the parasite requires superficial keratinized tissue to proliferate, and this kind of keratin is only ubiquitously available on host anurans after metamorphosis, when the keratinized stratum corneum is fully developed. I think this may be the most interesting part of the study, that potentially lethal costs may be accrued by a host species even when the tissue that is the primary target for infection is still not fully available to the parasite.

For me one of the most satisfying outcomes of this study has been the ability to export the experimental methodology to other labs, which we have done through our EU-funded project RACE (Risk Assessment of Chytridiomycosis for Europe’s amphibians, http://www.bd-maps.eu). Several researchers in several countries have benefitted from using techniques developed during this study, most importantly several graduate students. We’ve also employed our experimental system to explore relationships between climate change and chytridiomycosis (Garner et al. 2011 Global Change Biology) and investigate the evolution of the fungus itself (Fisher et al. 2009 Mol Ecol, Farrer et al. 2011 PNAS). In doing so, I believe we’ve been able to shine some light on the rather unpredictable and context-dependent relationships between Batrachochytrium dendrobatidis and amphibian hosts that are not highly susceptible to chytridiomycosis, but may still experience the lethal form of the disease.

We use cell culture flasks to house tadpoles individually through metamorphosis. This system allows us to replicate extensively while keeping the individual animal the unit of replication. Replicating treatments 30 or 40 times is easily achievable for most experiments using this approach. Not bad for a vertebrate.

 

INTECOL 2013, takes place in London August 18-23, see http://www.intecol2013.org/

We’ll be there! Will you?

More info on Oikos symposium and other activities will come soon!

The 11th INTECOL Congress, Ecology: Into the next 100 years will be held in London as part of the centenary celebrations of the British Ecological Society.The theme of the Congress is Advancing ecology and making it count.

Early-bird registration closes on 12^th May: http://www.intecol2013.org/5_Registration.html

Read about butterflies finding romance in the mountains in the new Early View paper “Simple rules for complex landscapes: the case of hilltopping movements and topography” by Guy Peer and colleagues. here’s Guy’s summary of the paper:

Mating on a hilltop

You are lost in an unfamiliar, hilly landscape. What shall you do? Most people would ascend the nearest hill and try to get a good overview. Butterflies may have much more limited vision, but they manage quite effectively in aggregating on mountain tops which serve as rendezvous for mating. An individual-based model which focuses on this “hilltopping” phenomenon identifies simple behavioural rules that can optimise mating success, and the success of mated females in finding habitat patches, across landscapes regardless of their complexity. One interesting rule is: when moving uphill, butterflies should respond strongly but not ‘perfectly’ to topography. A perfect response, without occasional random movements, would simply trap them on local summits. If such mild randomness might be adaptive, shall we adopt the rule and accept our imperfections? At least for butterflies, it clearly helps finding a mate.

Fighting overe a female on a hilltop

Guy Pe’er when chasing hilltopping butterflies in Israel, long ago when doing his PhD. While his “hilltopping model” is by now 12 years old, new results continue to emerge.

Look up, zombies are all around us nowadays! Even within science! In the Early View paper  “A critical analysis of the ubiquity of linear local–regional richness relationships“, Thiago Goncales-Souza and colleagues  goes on a zombie-killing adventure. Here is there summary of the paper:

Recently, ecologists have gone on a zombie killing spree, started by a blog post of Jeremy Fox here at the Oikos blog (link here). Dr. Fox defined zombie idea as having “survived decades of attacks from the theoretical and experimental equivalents of chainsaws and shotguns, only to return to feed on the brains of new generations of students.” He featured other zombie ideas such as “neutral = dispersal limitations” and the unimodal diversity productivity relationship. The post on his original zombie idea actually resulted in a peer-reviewed publication (Fox 2013) that, in his own words, has “No zombie jokes or other inflammatory rhetoric in it. I leave it you to judge if that makes the paper better or worse than the blog posts.” (link here).

We think that our publication fits into this zombie killing tradition. One of the most fundamental interests of ecologists since the early development of the ecological theory is the understanding of (potential) processes that drive local community structure. At a fundamental level, communities are structured by a combination of local environmental and regional processes (Ricklefs 1987).  The easiest and most traditional way to test whether regional or local processes affect local community structure consists of regressing local against regional species richness (the famous LSR-RSR relationships). The argument goes that communities controlled by regional processes are considered unsaturated, whereas communities controlled by local processes (such as species interactions) are considered saturated. Sadly enough, this argument survived indeed decades of attack (D. Srivastava, F. He and collaborators, and H. Hillebrand).

Sadder still, this method has kept on feeding on the brains of new generations of students, since it is used and featured prominently in ecology textbooks such as Begon et al. (Ecology: from individuals to ecosystems), Krebs (Ecology: the experimental analysis of distribution and abundance), and Ricklefs (The Economy of Nature and Ecology). Probably every ecology student has heard about the ubiquity of regional processes as drivers of local community structure using this method.

In addition to these fundamental problems, Szava-Kovats and collaborators in Oikos showed that the statistical test for detecting the linearity of the relationship is biased towards linear relationships, and moreover provided an unbiased method (called log-ratio method). In this Forum paper, we reevaluated the evidence for the ubiquity of linear LSR-RSR relationships by comparing the biased conclusions with the unbiased method, and found:

1. In 113 relationships found in 47 studies, 70% and 30% were considered unsaturated and saturated, respectively, when using the biased method. However, by using the unbiased log-ratio method we found no prevalence of either unsaturated (53%) or saturated (47%) communities (Figure 1);
2. 40% of the studies using the biased method were misclassified (i.e., mistakenly found an unsaturated pattern when it was saturated or vice-versa) and thus reached wrong conclusions.
3. 50% of the examples of LSR-RSR relationships used in four (classic) ecology textbooks were misclassified.

Our conclusions thus add a new weapon in the arsenal against the zombie idea of interpreting local-regional relationships based on the linearity of the relationship. We showed that the last argument in favor of the method (its ubiquity) was based on a biased statistical method. We argue instead that future studies should consider the reciprocal interactions between regional and local such as those that take advantage of the metacommunity theory to understand the relative influence of regional and local processes on local community.

While studies of LSR-RSR relationships were instrumental to the development of the ecological curriculum, we hope that we can now finally put this zombie idea to rest and move on. As a final note, one of the reviewers for this manuscript was … non other than Jeremy Fox, zombie slayer par excellence.

We are very happy to welcome Prof. Susan Harrison from UC Davies, USA, to our editorial board.
  

My research seeks to understand the processes that shape and maintain plant species diversity at the landscape scale, where small-scale forces such as competition and facilitation interact with large-scale forces such as niche evolution and dispersal.  In the past few years, one particular focus has been to understand what characteristics of plant species and communities make them more or less susceptible to climate change, as well as to other interacting perturbations like fire, grazing, and invasion.  We’ve found that plant communities on nutrient-poor serpentine soils seem to respond less strongly to natural and experimental climatic variation than other communities, but we don’t yet understand the roles of soil properties, plant traits, and emergent community properties in causing this pattern.

Read more:  http://www.des.ucdavis.edu/faculty/Harrison/

They look the same, but perform so differently. And act differently against each other. Cryptic amphipods are dealt with in the Early View paper “Phenotypically similar but ecologically distinct: differences in competitive ability and predation risk among amphipods” by Rickey D. Cothran and colleagues. Read their summary here:

Traditionally, species that look alike were thought to be unlikely co-inhabitants due to competitive exclusion. However, newer theory suggests that a mix of ecological similarity that limits performance asymmetries that lead to competitive exclusion and slight differences in niche use may maintain species diversity. We provide data on the relative competitive ability and predation risk for three amphipod species that co-occur in lakes in North America. Until recently, these species were only differentiated using molecular markers (see picture). We discovered that slight differences in phenotype lead to differences in how well these species compete and deal with predators. We also found that the two species that show the strongest overlap in distribution within lakes are very similar when it comes to their competitive ability and predation risk. Our work suggests that a mix of niche differentiation and ecological similarity are maintaining amphipod species diversity in lakes.

Cryptic amphipod species before (top) and after (bottom) preservation in 70% ethanol. From left to right: species A, species B, and species C. All animals are females.

Picture caption: Cryptic amphipod species before (top) and after (bottom) preservation in 70% ethanol. From left to right: species A, species B, and species C. All animals are females.

Will the use of “real” connectivity between communities improve metacommunity models? Read more in C.Moritz and colleague’s Early View paper: “Disentangling the role of connectivity, environmental filtering, and spatial structure on metacommunity dynamics”. Here’s their summary of the paper:

For decades, the environment has been proven to structure biodiversity. However, dispersal of organisms is also  a process that helps structuring and maintaining biodiversity in local communities. The problem is that  connectivity between communities (the fact that these communities are linked, resulting from the dispersal  process) is often assessed using a more or less simple function of geographic distance. Theoretical metacommunity models can incorporate both environmental and dispersal processes, but empirical  studies considering real connectivity instead of a function of geographic distance are more scarce. In our work,  we have included real connectivity measures to analyse polychaete community structure in the Gulf of Lions (NW  Mediterranean Sea) at different spatial scales. Our results are not trivial…and equivalent methods should be  applied to other ecosystems (terrestrial or marine) to continue quantifying the importance of dispersal on  biodiversity, either for particular species of interest or for entire communities.

Nice to see that nature provides other kinds of interactions than nasty predation, competetion and parasitism! Christian Schöb and coworkers have studied the importance of “nursing” plants – plants that fascilitate for other plants – in community ecology. Read their Early View paper “Direct and indirect interactions co-determine species composition in nurse plant systems”.

Here is a summary of their study:

Our motivation to build a framework based on observational data in order to disentangle direct nurse effects from indirect effects among beneficiary species was twofold:

1) In some very common nurse plant systems, such as alpine cushion plant communities, the removal of the nurse to eliminate the direct effect and unambiguously estimate interactions among beneficiary species is simply not feasible.

The physical removal of the nurse cushion Arenaria tetraquetra ssp. amabilis growing in the Sierra Nevada Mountains in Spain would destroy the beneficiary species growing within the cushion canopy; in particular because beneficiary species often root in the organic matter accrued under the cushion.

2) Even in nurse plant systems where the physical removal of the nurse is feasible, taking away aboveground nurse parts does not remove the permanent effects of the nurse, e.g. the effects on soil properties including texture, resources and microbial communities.

An intact Retama sphaerocarpa nurse plant system in the semi-arid lowland of southeastern Spain with the nurse shrub and its understory community of beneficiary species.

The removal of aboveground parts would not remove the whole effect the nurse shrub, such as accumulation of soil organic matter and its specific communities of soil bacteria and fungi, which all together influence beneficiary species even after the nurse plant has been removed.

In our article we propose a simple but powerful mathematical framework to take apart direct effects of the nurse on its associated community from effects of interactions among beneficiary species. Our results showed facilitative effects of the nurse on its beneficiary species whereas interactions among beneficiary species where mostly competitive. Both interactions contributed significantly to the composition of the beneficiary plant community even though the direct nurse effect was ca. five times stronger than the effect of the interactions among beneficiary species. Interestingly, these patterns where similar in the two nurse plant systems studied even though they differed considerably in abiotic conditions (high alpine vs. semi-arid lowland) and growth form of the nurse (cushion plant vs. shrub). Our data therefore indicate functional parallelism of different nurse plant systems and highlight the complexity of species interactions within plant communities.

Hello everyone, my name is Ross Boucek and I am PhD student at Florida International University. Oikos has asked me to write about our Early View paper “No free lunch: displaced marsh consumers regulate a prey subsidy to an estuarine consumer” where we investigate the value of food subsidies to recipient consumers as well as what controls the amount of food subsidies available to them.  Food subsidies are resources that enter an ecosystem from another place, and add on to the resource base that is already available within the system. Subsidies in some instances can be almost considered a bonus, like getting cash for your birthday in the mail.  If you are on a graduate student stipend, birthday cash subsidies can go a long way! Because of the predictability of birthday cash, many graduate students budget these cash bonuses into their spending well before they arrive.  Therefore, if for some reason these checks get lost in the mail, or they are for less money, we could be in some trouble!

Graduate students and their reliance on birthday money is very similar to how some animals rely on food subsidies to survive.  One particularly charismatic example of consumer-subsidy interaction is bears and salmon in the U.S. Pacific Northwest.  In the fall, these bears congregate around rivers and streams to gorge themselves on salmon that predictably migrate from the oceans to spawn. These salmon subsidies help bears build necessary fat reserves that play a major role in their survival and reproduction over the winter. Because of the importance of food subsidies to consumers, biologists and ecologists have gone to great lengths to identify where subsidies occur in nature, and more importantly what controls how much of the food subsidies reach recipient consumers.

Diagram of the relationship between marine salmon subsidies and bears

Moving back to the bear-salmon subsidy interaction, in some areas of the U.S. Pacific Northwest, sea lions have figured out salmon are easy prey during their spawning migration; such that some sea lions track salmon up rivers, and pig out on these spawning fish, preventing them from reaching bears. The interception of these salmon subsidies by sea lions can be so intense, that they can reduce salmon available to hungry bears waiting upstream by as much as 65%.

Diagram showing how sea lions reduce salmon subsidies to bears

This brings me to my research.  I work in the Florida Everglades, more specifically, where the iconic Everglades marshes or the “river of grass” joins the beautiful tropical mangrove estuary.

The study area of our research, located at the marsh-estuary interface in the Southwest Everglades

At this interface between the marsh and the estuary, during the winter and spring, rainfall decreases, causing freshwater marshes to dry.  When these marshes dry, large numbers of small-bodied freshwater fishes are forced into the estuary. At the same time that these prey enter the estuary, estuarine fish predators triple in abundance presumably to gorge on the marsh fish prey forced into the estuary.  Thus at the Everglades ecotone, estuarine predators function similarly to the bears in the Pacific Northwest, and small bodied marsh prey are like the salmon. However, similar to the sea lions, these small bodied fishes are accompanied by large-bodied fish predators that also live in the marsh that can intercept and remove or reduce fish prey subsidies to the estuarine consumers.  With all of this in mind, my research questions were 1) how important are marsh prey subsidies to estuarine consumers? And 2) how much of this subsidy is being removed by marsh predators?

Diagram showing the relationsship between estuarine and marsh predators and marsh prey subsidies at the marsh-estuarine interface of the southwest Everglades

Our results show, like the salmon-bear example, that estuarine predators gorge themselves on these marsh prey subsidies. Consequently, the consumption of this subsidy makes estuarine predators roughly 15% fatter than they were before.

However, like the sea lion example, freshwater marsh predators consume about 60% of the fish prey that enter the estuary, leaving only 40% for the estuarine consumers.   The regulation of this subsidy to snook, the estuarine predator, could influence how much energy snook allocate to reproduction each year.  Snook spawn in the early summer to mid fall. Therefore the weight snook gain from this subsidy in the spring could go to egg production in the summer, thus increasing reproductive output.  If marsh predators decrease in abundance, then the amount of subsidy available to snook could increase, which may allow snook to invest more energy into reproduction and increase spawning success.  My current research is investigating just this question, whether or not larger prey subsidies, facilitated by the loss of marsh predators, result in increased spawning effort by snook.

Understanding the dynamics behind this subsidy could have important implications for South Florida.  In South Florida, snook are an important recreationally sought after fish.  In fact, snook are the 5^th most targeted fish in the entire east coast of the United States, despite only occurring in South Florida. The money spent from anglers fishing for snook generates substantial amount of revenue for local businesses.  Therefore, knowing the drivers behind snook population dynamics like the regulation of food subsidies will help us better understand the provisioning of ecosystem services such as fisheries in the Everglades.

The colder, the bigger, suggested Bergman in 1848. In 2013 we publish a paper testing Bergman’s rule on a large data set. Showing…well find out in “Bergmann′s rule in mammals: a cross-species interspecific pattern” by Marcus Clauss and his co-workers. Below is their background story to the study:

I first learnt about ‘Bergmann’s rule’ (that among closely related species, those living at higher latitudes/at colder temperatures are larger) in school. It was one of the biological facts I had always considered a background fact that is unquestioned.  

When preparing a manuscript on the reproductive seasonality of ruminants (Zerbe et al., 2012) we collated various biological data on ruminants, including body mass and mid-latitude of their geographical range, and before testing relationships of these data with our proxy for seasonality, we tested them amongst themselves for potential correlations. We did this without accounting for the phylogenetic structure of the data (ordinary least squares) and with such an accounting (phylogenetic generalized least squares, pgls).

We were not surprised when we found a relationship between latitude and body mass in our phylogenetic analysis – because this simply reflected Bergmann’s rule. The fact that this relationship was not significant in conventional statistics, but significant in pgls, just supported the notion that the rule holds among closely related species, not just any species you lump together. For us, this was a minor side-dish result in our set of analyses, and one we were not excited about, because it simply confirmed what we knew from school. In a quite similar way, our ruminant dataset supported, for example, Rensch’s rule (which was cool for our co-author that had the same name). But when we prepared the manuscript, and searched for other papers to cite in connection with our side result, we realized that Bergmann’s rule had, as far as we could find, not been analysed in this fashion among mammal species, not in ruminants, and surely not in a larger mammal dataset. Literature on Bergmann’s rule in mammals most often dealt with the intra-specific side of the phenomenon or with mammal assemblages, but not on the taxonomic/interspecific level. So we expanded the dataset beyond the ruminant species for which we had seasonality data, to comprise all mammals (based on availability of data in the PanTheria database). Again, we found the same effect: the relationship between latitude and body mass was significant if the phylogenetic structure of the dataset was taken into account. In a sense, we felt like having found a simple proof for a school lesson that had not been provided so far. This does not mean we claim to be first, best, closest, whatever, to proving Bergmann’s rule – we just found a simple, maybe elegant way to demonstrate it. Actually, once you start looking at individual taxonomic subgroups or certain geographic ranges, the picture becomes less simple – but that’s in the paper.  

For us, several lessons came with working on this topic. One is that the statistical procedure (pgls, sometimes called ‘phylogenetically controlled statistics’) is not only a quarrelsome one that one has to apply nowadays to get a paper published, but actually facilitates, in special circumstances, the detection of a pattern that would not be evident from simply plotting the data, or from ‘conventional’ statistics. So we tried to understand how patterns would look that yield different results in conventional and phylogeny-informed statistics, drawing on textbooks on the matter, and produced some schematic graphs to get a mental grasp on this (provided as a supplement to our paper). In my experience, there are quite some examples where a relationship that is significant in conventional statistics is no longer so in phylogenetic statistics (which then needs to be interpreted), but there are very few examples where a relationship is not significant in conventional stats but clearly is in phylo-stats.  

The other lesson came from going through the literature – at some stage, we decided to try to locate the original source itself, Bergmann’s own account, which was sometimes described as ‘hard to get at’ – and were surprised that you could simply download the whole text from the net (it is now part of the google books resource pool). Reading this text was quite some fun, due to the old style it was written in. From other literature, we had gained the impression that Bergmann formulated his rule for mammals, and were therefore surprised to see that he actually developed it, and supported it, using birds. And all the examples Bergmann used himself were between, not within, bird species, so no need to debate whether he meant it on an inter- or intra-specific level. Because the text is written in German, we decided to provide a relatively detailed translation of larger parts of it, so that others could get a picture of how he built his argument. I personally especially cherished his concluding comment, where he cautions the reader that in trying to support his hypothesis, he might have looked at the actual evidence in a biased way, and that therefore independent tests would be welcome.    

For the April issue, we chose the following two papers as editor’s choice according to our motto of synthesizing ecology. Mumby et al. (2013) discuss various articles that either support or reject the hypothesis that coral reefs might be able to exist under certain conditions in two alternative stable states (ASS): a coral-dominated and a macroalgae-dominated state. Given the fact that the existence of multiple attractors is controversial, synthesis needs to be created by compiling various forms of evidence. Mumby and colleagues provide such an overview of evidence by providing analyses of the literature and the available empirical and theoretical data. By means of this integrated approach, they conclude that the most compelling evidence, which combines ecological models and field data, is far more consistent with multiple attractors than the competing hypothesis of only a single, coral attractor. This message warns managers that degraded reeds might never be able to be restored once dominated by macro-algae. Read Peter Mumby’s summary of the paper here

The second paper we selected is Baiser et al. (2013) testing the ability of metacommunity models to predict the network structure of the aquatic food web found in the leaves of the northern pitcher plant Sarracenia purpurea. It is the central aim of metacommunity theory to elucidate the relative impact of local and regional processes on local community structure. The structuring processes have, however, been predominately inferred from statistical modelling. The work of Baiser and colleagues takes an elegant approach to formally test to which degree patch-dynamics, species-sorting, mass-effects, and neutral metacommunity models, as well as three hybrid ones are able to predict observed patterns of the aquatic foodweb structure within these plants. By merging empirical data and more mechanistic models they test the probability that dispersal and sorting processes are important mediators of food web structure. While such integrated empirical-theoretical approaches have been developed for other ecological questions, Baiser et al. here demonstrate its usefulness for understanding drivers of food web structure.

Both papers as Open Access.

From the April issue 2013 onwards, Oikos will have a photo illustrating ecology in action on it’s cover.

To find the right photo for this year’s cover, we had a photo competition during winter. The happy winner of the competetion is Sascha Rösner, Marburg, Deutschland. See more of his photos here: www.pixeldiversity.com

And here is our new cover:

And here, Sascha tells us how he took the winning photo:

Wildlife photography often entails long travels to distant and remote landscapes that harbour a particular species of interest. This picture of two sawfly caterpillars (Nematus spec.), however, was taken just three meters of the front door of the photographer’s home. In the front yard, a small willow tree (Salix spec.) was densely populated with hundreds of these caterpillars. An easy opportunity to take the camera from indoors, attach a macro lens to the camera, mount it on a tripod, and take pictures (in fact, still wearing slippers). By chance, two of these guys apparently fed synchronously in the center of a leaf. Within 24 hours, the tree was completely naked, the caterpillars “abseiled” to the ground, and dug into the soil where they would morph into the imago flies some weeks later. Canon EOS 20D, EF 100 mm 2.8 @ f 7.1, ISO 100, tripod, remote control.

It has been debated for a while…are males really necessary? Find out how fish of the genus Chrosomus solve the small problems associated with asexual reproduction, in the Early View paper “Diets of sexual and sperm-dependent asexual dace (Chrosomus spp.): relevance to niche differentiation and mate choice hypotheses for coexistence” by Jonathan A Mee and co-workers.

Here’s a short summary of the study:

In order to persist, sperm-dependent asexuals must be ecologically divergent and/or more sperm-limited compared to their sexually reproducing hosts.

It’s easy to be fascinated by sperm-dependent asexual species – they’re one of those oddities of natural history that, collectively, are the reason many of us became students of biology. These all-female “Amazons” require a male (or just their sperm) of a sexually reproducing host species to provide the trigger for egg development and reproduction, but, in most cases, discard the male’s genome.

In addition to being a fascinating natural oddity, the existence of sperm-dependent asexuals raises an interesting scientific question: how do sperm-dependent asexuals coexist with their host species?  All-female asexuals have a great advantage over sexuals – by producing no males, the asexuals have twice the potential population growth rate relative to the sexuals.  But, in the case of sperm-dependent asexuals, vastly outcompeting the sexuals (i.e., eliminating the source of sperm) would eliminate the ability to reproduce.  There are two general mechanisms by which sperm-dependent asexuals and their sexual hosts can achieve stable coexistence.  First, sufficient ecological divergence between the sexuals and asexuals would avoid competitive exclusion.  Second, if males prefer mating with sexual females rather than asexual females, asexual females would be more sperm limited (and have reduced reproductive output) relative to sexual females.

Our contribution to understanding how sperm-dependent asexuals coexist with their sexual hosts examined the combined influence of these two mechanisms (ecological divergence and male mate choice) on the coexistence of sperm-dependent asexual species and their sexual hosts – previous work only considered each mechanism independently. We integrated the insights of mathematical modeling and empirical data on ecological divergence (from two natural populations of the sperm-dependent asexual fish, Chrosomus eos-neogaeus) to conclude that a combination of both mechanisms may be required for coexistence. This integrated approach is valuable to understanding many ecological and evolutionary processes.

Ever thought about why an orange is orange while an apple is green? And a blueberry blue and blackberry black, while a raspberry is red? Well, one explanation – seasonality – is studied in the new Early View Paper  “Fruit color and contrast in seasonal habitats – a case study from a cerrado savanna” by Maria Gabriela G. Camargo and co-workers. Here is their short summary of the study:

Examples of fruits with different colors. A. green; B. multicolored; C. yellow; D. black; E. multicolored; F. brown; G. multicolored; H. red.

Fruit color is an important signal for diurnal seed dispersers, mainly for birds, and the contrast between the fruit and the background is regarded as more important than the color per se for fruit detectability. However, the contrast between fruit displays and their background are not necessarily constant in seasonal habitats where part of leaves is shed in the dry season.

We thus hypothesized that the contrast between fruit displays and their background vary throughout the year in a seasonal habitat and if this variation is adaptive, we predicted higher contrasts between fruits and foliage during the fruiting season.

To verify our hypotheses we used reflectance measurements of fruits and leaves and contrast analysis. We also accessed a six-year data base of fruit ripening according to the fruit color (red, yellow, black, brown and multicolored) for a woody community in a cerrado-savanna vegetation, southeastern Brazil. The cerrado is subjected to a seasonal climate, with a wet summer between October and March and a dry winter between April and September, when the leaf background get yellowish.

Circular histograms for the frequency of fruiting onset dates per fruit colors in a woody cerrado savanna community, southeastern Brazil.

We found that black, and particularly red fruits, that have a high contrast against the leaf background, were highly seasonal, peaking in the wet season. Multicolored and yellow fruits were less seasonal, not limited to one season, with a bimodal pattern for yellow ones, represented by two peaks, one in each season. We further supported the hypothesis that seasonal changes in fruit contrasts can be adaptive because fruits contrasted more strongly against their own foliage in the wet season, when most fruits are ripe. Hence, the seasonal variation in fruit colors observed in the cerrado-savanna may be, at least partly, explicable as an adaptation to ensure high conspicuousness to seed dispersers.

Mean leaf reflectance curves during the dry and wet seasons for 49 species of the woody cerrado savanna community, Southeastern Brazil.

To consider at your Friday dinner tonight: Sex-biased diets affect the ecology of other species in the surroundings. Read more in the new early View paper “Antelope mating strategies facilitate invasion of grasslands by a woody weed” by Shivani Jadeja and colleagues. To get a good feeling of the antelope and the seeds that the males eat, read Shivani’s beautiful description of the wildlife reserve in western India, in her summary of the paper:

Mesquite (Prosopis juliflora) pods

In Velavadar National Park, a grassland wildlife reserve in western India, invasive mesquite trees (Prosopis juliflora) obstruct the horizon, where the land meets the sky. The dominant woody plant in the area, mesquite juts out as green crowns among the drying grasses that give the grassland a hue of yellow, red and olive streaks in the winter and summer. Velavadar is home to a large population of the threatened native antelope, blackbuck (Antilope cervicapra). Male blackbuck defend territories in open grasslands; these territories are either solitary or in clusters called leks. The classical lek in Velavadar, the size of a football field, may have more than ninety rutting males during peak mating season. During this time, the lek turns into a battle field where males perform strenuous displays and engage in fierce fights to defend their territories. Females visit the lek and seem to use a variety of information to choose a male to mate with. Males use urine and dung to create huge scent marks on their territories. These dung-piles can be seen as black dots from outer space (Look at blackbuck dung-piles on Google satellite images at 22° 2’54.82″N and 72° 1’20.78″E).

Fruit removal by male blackbuck (Antilope cervicapra) captured in a camera trap

Seed deposition through dung on a male blackbuck mating territory. Inset: A large dung-pile on the classical lek

Presence of mesquite seeds in blackbuck dung

As blackbuck prefer open habitats, we predict that this concentrated seed dispersal by males will result in a positive feedback process where territories, which are typically in open grasslands, are modified into woodland patches, following which  males shift their territories to more open areas. We also predict that this male-aided conversion of grasslands to mesquite woodlands will negatively affect this open plains antelope species and cause shifts in mating system and social organization and a reduction in population size. Thus, here is one mechanism of spread of a woody invasive in grasslands, where one sex of a disperser, here male blackbuck, through its extreme mating behaviour, is planting seeds in new habitat, and perhaps negatively affecting its own lifestyle.

Seedling growing in a dung-pile on a blackbuck mating territory

Taylor´s power law and bird populations are studied with in the new Early View paper “Interspecific differences in stochastic population dynamics explains variation in Taylor’s temporal power law”, by Marit Linnerud and her coworkers. Here’s Marit’s summary of the study:

Taylor’s power law – an oldie but goodie!

Taylor’s power law is like the little black dress of ecology, a general law that fits every species regardless of size or other personal characteristics.  According to the law the variance of population abundance in either time or space can be described by a function of the mean. A reasonable null expectation following from the definition of the variance is that as the abundance of a population increase by one unit on a logarithmic scale the variance is expected to increase by two logarithmic units, resulting in a slope of two. However, empirically the slope is often less than two, thus revealing some interesting ecological dynamics. Although the causal mechanism behind the law is not agreed upon, it seems likely that several factors are at play. A theoretical framework based on stochastic population dynamics provides testable predictions of what causes the deviations from the expected slope of two.

In our recent study we estimate the temporal mean-variance relationship for a large number of British bird populations. There were two significant challenges. Firstly, we could not ignore that sampling in itself could bias the estimates of the variance and secondly the estimated of variance increases with the number of years the population have been studied. Taking this into account we evaluated how the different deterministic and stochastic factors known to affect temporal population dynamic influenced the slope of the power law. It turns out that differences in demographic stochasticity among species were the main explanation of the variation in the slopes of Taylor’s power law.

I would so much like to see someone using Hari Sridhar, Ferenc Jordán and Kartik Shankers paper “Species importance in a heterospecific foraging association network” as a basis for a study of humans on cocktail parties. Which small groups may be the core of highly important individuals (instead of species)? Is the same group of people important if they go to a party in another place? Or to a scientific conference in another research area? Or are humans not at all like birds?

Here is Hari’s background story to the study. The beautiful drawing is made by Rangu Narayan.

Chance and luck played a big part in the making of this paper. It was early 2008, and I had just begun my doctoral work on mixed-species bird flocks, when Ferenc visited my department. Ferenc specializes in using network approaches to tackle problems in ecology. In a talk during his visit, he mentioned that ‘network thinking’ was particularly useful in two ecological contexts: (1) to understand interactions among individuals in animal social groups (2) to understand interactions among species in communities, e.g. foodwebs. When we heard this, both Kartik (my PhD supervisor) and I immediately realized the value of network thinking in my doctoral work because mixed-species flocks fit both the contexts that Ferenc highlighted. Each mixed-species flock is a social group built on interactions among individuals of different species; but across multiple such flocks in an area, populations of species are linked in a community-level species interaction network. We spoke to Ferenc and he readily agreed to help us, since he too was keen on trying his hand at a new ecological system.  Given our different geographical locations (Ferenc was based in Trento, Italy, and Kartik and I in Bangalore, India), the plan was to work the collaboration entirely over email. But another lucky break meant that I could go to Ferenc’s institute in Italy to work on the project. My fieldwork was supported by a grant from the International Foundation for Science (IFS), of which a large portion remained unused till the end.  IFS allowed me to use this money to travel to Italy for two weeks in early 2012. Over endless cups of coffee and food at an Indian (!) restaurant in Trento, Ferenc and I built and analysed the flock networks for this paper.

 This collaboration had other useful spinoffs. Ferenc came back to India in 2012 to conduct a network analysis workshop as part of a student conservation conference in Bangalore that Kartik and I were involved in organizing. Kartik and Ferenc are also putting together a special issue on ecological networks for a conservation magazine called Current Conservation, which will include a non-technical piece based on this Oikos paper.

Do you like trying new food items? I do. And many herbivore insects seem to do so as well. Invading alien species, yummy yummy! How these interactions affect the ecology of the invaders is studied by Matthew L. Forrister and Joseph S. Wilson in “The population ecology of novel plant–herbivore interactions”. Here’s their background to the study:

Everyone knows that weeds are everywhere these days, and most ecologists know that native insects often like to eat exotic plants.  That dynamic (native herbivores utilizing novel hosts) has been very productive for evolutionary biologists (think about the apple maggot fly on apple or the soapberry bug on goldenrain trees), and has become increasingly useful for ecologists who realize that we can watch novel interactions and communities assemble before our eyes.

The ubiquity of interactions between native herbivores and novel plants has led to an imbalance in the ratio of empirical to theoretical work.  Moreover, some of the relevant theoretical work (for example on the evolution of niche width) is not always accessible to the average field biologist observing caterpillars eating weeds.  Our motivation in writing this paper was to provide an easily accessible conceptual framework that might serve to organize and focus experimental approaches.  For example, studies are often reported in which the “preference-performance” relationship is examined using native insects reared on native and exotic hosts.  We believe that the focus on that particular relationship demonstrates a certain inertia in the literature that should be overcome, because (for one thing) a rather definitive meta-analysis of that issue has been recently published (Gripenberg et al. 2010 Ecology Letters 13:383-393), and moreover there are many other facets of insect life history that need to be studied, such as interactions with natural enemies, indirect interactions with other herbivores or behavioral factors that affect realized fecundity.

In addition to making the rather fundamental point that our studies need to go beyond the performance of juvenile herbivores and the preference of ovipositing females, we offer some hypotheses to challenge assumptions and spur future work.  We present our hypotheses in qualitative, graphical format in the spirit of the late Robert MacArthur.  Some quantitatively-sophisticated readers might find this approach simplistic, but we hope that other readers will find it useful.  For example, we ask about the shape of the relationship between dispersal ability, population growth rate on a novel host, and the rate at which a new host is utilized.  Also in the spirit of MacArthur, we hope that other researchers will be inspired to propose alternative hypotheses, which is something that we believe the graphical (as opposed to verbal) format encourages.

How consistent are field-guides and atlases? Enough to be used as sources in ecological research studies? Jay Fitzsimmons has checked and has the answer! Find out in his new Early View paper “How consistent are trait data between sources? A quantitative assessment”. Below he tells us what made him conduct the study:

I compared several field guides and atlases to see whether they were consistent in what they said about species’ traits.  The proximate reason why I did this research is that, given the popularity of trait-based research, I wanted to determine how consistent trait data were among authoritative sources.  The ultimate reason why I did this research is that I’m a paranoid city slicker who worries over how little I know about my study species.

Trait-based ecology is increasingly popular, with researchers evaluating whether species’ traits are related to a variety of ecological factors (e.g., extinction risk, invasiveness).  In my PhD I did such an analysis myself, evaluating the relationship between butterfly species’ traits and their rates of northward range shift in Canada over the 1900s (not yet published – it’s only been two weeks since my PhD ended so give me a break).  The advice given to me on how to obtain species’ trait data was “just use an atlas or a field guide.”  This is when my paranoia alarm started ringing.  Which atlas or field guide should I use?  Do they all say the same thing?

 While I love and respect natural history (I volunteer as Journal Manager for The Canadian Field-Naturalist – www.canadianfieldnaturalist.ca), I am not a great naturalist myself.  I cannot even identify most of Canada’s butterflies, never mind critically evaluate the accuracy of their trait data.  This is a serious problem for macroecology that isn’t given the critical attention it deserves: researchers using fancy models and elaborate analyses can miss critical issues if they don’t know the natural history of their study species.  Non-naturalist macroecologists can miss interesting results that merit follow-up, or wonky results that could indicate coding errors.

 So which source should a paranoid, butterfly-ignorant macroecologist use?  All the sources of course!  Ok, not all the sources (not by a long shot), but I used five authoritative sources authored by recognized experts.  I entered data from each source for 22 traits for 263 Canadian butterfly species.  I compared trait data for species across sources: do different sources say the same things about species?  I found some traits to be very consistent across sources, and others worryingly inconsistent.  In general it seems that subjective traits (e.g., habitat association) were less consistent than more clearly-defined traits (e.g., wingspan, over-winter stage).  This suggests results from single-source trait studies may depend in part on which source was used for trait data.

It was a pleasure to do this work, and to vindicate my paranoia (I can put the tinfoil hat away for another day).  I hope others do similar comparisons of field guides and atlases for other taxa and regions to reveal how general my findings are, and what effect such inconsistency has on trait-based research results.

How do animals decide how to forage? In the new Early View paper “How a simple adaptive foraging strategy can lead to emergent home ranges and increased food intake” Jacob Nabe-Nielsen and colleagues demonstrate that it only requires a few simple behavioural rules to produce most of the complex movement patterns observed for harbour porpoises.

What is it that makes an animal stay within more or less the same area for weeks or months before eventually moving to a new place? Surely it must have been feeding in the area, but how does it decide when it is time to leave? One of the central questions in behavioural ecology is whether animals have evolved many different kinds of behaviour, where each behavioural response is fine-tuned to a particular condition that the animals encounter in nature, or if a few simple mechanisms are sufficient to enable them to respond optimally in a wide range of conditions.

The simulated harbour porpoise movements closely corresponded to those of satellite-tracked animals.

The harbour porpoise (Phocoena phocoena) is an example of an animal species that displays very complex movement patterns. Porpoises often stay within relatively well-defined areas, or home ranges, where they presumably prey on various species of small fish before moving to new areas. In order to investigate whether a few different cognitive mechanisms could be sufficient to generate this complex behaviour, we developed a simulation model that included only two different kinds of behaviour. In the model the food was distributed in minute, scattered patches. Animals that had recently found plenty of food moved at random, much like cows that walk at their own pace in a field with lots of fresh green grass. Animals that had not been able to find food for some time became increasingly attracted to the patches where they had found food in the past. We let the animals’ ability to find their way back to previously visited food patches be governed by a spatial memory. It turned out that the combination of these two kinds of behaviour enabled home ranges to emerge, and when the animals’ memory about previously visited foraging sites decayed at a particular rate the model was able to produce movement patterns that closely resembled those observed for satellite-tracked porpoises in Danish waters. The right balance between the two kinds of behaviour also allowed animals to maximise their food intake. This suggests that it could be selectively advantageous for animals to base their decision on how to forage on a few, simple behavioural mechanisms.

We now check all submitted manuscripts for possible plagiarism using iThenticate.This means that all manuscripts are compared to more than 32 billion webpages, more than 34 million scholarly content items and more than 91 million news pages, books and magazines (and yes, these numbers are “plagiated” from iThenticate’s webpage…).

How similar are manuscripts generally to already published stuff? Most manuscripts show between 5 and 15% similarity.

And where is the limit for plagiarism? When a paper show more than 25-30% similarity with other published material, we do a thorough check for the similarities.

Reference lists, protocols in Methods and author adresslists may generate high similarities that are not really plagiarism. When high similarities are found in Results and Discussion, we act.

So it’s no use trying the copy and paste method for Oikos manuscripts…

One of the most cited papers in Oikos, during 2011 (published 2009 and 2010) is “New perspectives for estimating body condition from mass/length data: the scaled mass index as an alternative method“, by J Peig and AJ Green.

Here, Jordi Peig gives a short summary of the paper and an explanation to it’s impact:

Body condition (physical or nutritional status) is a widespread concept in the ecological literature. Although usually poorly defined, it encapsulates the animal’s health, quality and vigour, and hence its biological fitness. Scientists have used different approaches to estimate BC, but those based on morphometry and particularly on mass-length relationships have been adopted for routine use due to the ease of application and their ‘a priori’ conceptual simplicity. Briefly, morphometric indices attempt to quantify how heavy is an organism for a given body size, because the extra mass indicates more fat and protein reserves to overcome periods of food scarcity or high energy demand in general. However, larger animals will be inherently heavier, and vice versa, so the standardization of body size is the central challenge that underlies all morphometric methods, and is the subject of our paper. Many mathematical formulas and statistical methods have been proposed to standardise body size, yet there is still much debate among scientists as to the most suitable method.

The work published in Oikos has been popular partly because so many studies included attempts to establish the influence of body condition in population ecology. The idea of the paper was born in 2006 when distinct BC indices reported in the literature yielded opposite results when applied to my own data on small mammals. I found that those contradictory results were each scientifically plausible and arguable from an ecological viewpoint, hence the need to rethink the nature of these methods. After reading in and around the subject, including biostatistics, theoretical biology and epidemiology, I conceived the Scaled mass index. Because of the intrinsic tendency within sciences towards specialization, different disciplines have promoted and advocated their own methods (including the Body Mass Index used in medicine), and I searched for a common, unifying approach. With this complexity in mind, and the difficulty of publishing in this area for a PhD student (introducing alternative methods inevitably meets some scepticism and resistance) led me to seek collaboration with my co-author Andy Green, who had previously published in this field. From our first contact by email Andy was enthusiastic, and made substantial improvements to the manuscript. My original draft was prohibitively long for modern journals, and part of it went into a sister paper in Functional Ecology in 2010.

In the Oikos paper we attempt to explain the complexity of the BC issue from the fundamental viewpoint of allometric growth, and develop the Scaled Mass Index from that perspective. Amongst the papers that have cited our work, there are good independent examples of how our index outperforms previous methods. We can only hope that our future contributions on this topic become as successful as the Oikos’ paper.

 

Thumb’s out when the mite Spadiseius calyptrogynae needs to move to a new host plant. It can’t get their on it’s own, so it simply hitchhikes on bees, bats or beetles. Emanuel H. Fronhofer and co-workes have studied this in the new Early View paper “Picky hitch-hikers: vector choice leads to directed dispersal and fat-tailed kernels in a passively dispersing mite“. Here is Emanuel’s summary of the exciting study:

Tropical species diversity can be so high that while walking through a lowland rainforest it may be difficult to see two individuals of the same tree species. This phenomenon has fascinated generations of naturalists, but at the same time such high diversity represents a considerable challenge for any organism that, because of its biology, has to find another tree of a certain species to feed on, for example. How do specialized mutualists, predators or parasites manage to find their host(s)? This problem is especially relevant and critical for a lot of small, non-mobile species that occupy ephemeral habitats, such as small ponds, dung or, as in this study, flowers.

In this context, we have studied the dispersal strategies of a neotropical phoretic flower mite, that uses a number of different animal vectors – bats, beetles and bees – in order to hitch-hike from one host plant to the next. These mites (Spadiseius calyptrogynae) are specialized to their host plant, an understorey palm (Calyptrogyne ghiesbreghtiana), while the flower visitors and potential dispersal vectors are generalists.

The long distance disperser (Chasmodia collaris) on a male inflorescence of the palm Calyptrogyne ghiesbreghtiana (left). The detail (right) shows the phoretic mites (Spadiseius calyptrogynae) shortly after boarding their dispersal vector. Photo: E.A. Fronhofer.

Using a dual approach that combines field observations with experiments and individual-based modelling we find that our study species shows a highly developed capacity to discriminate between potential dispersal vectors based on chemical cues. These mites choose their dispersal vectors in order to optimize their dispersal kernel, i.e. the distribution of dispersal distances. The evolutionarily stable dispersal kernel is a mixed kernel resulting from short distance dispersal with bees (Trigona fulviventris) and rare long distance dispersal events with beetles (Chasmodia collaris). This results in a fat-tailed distribution of dispersal distances and additionally guarantees directed dispersal towards especially suitable habitat, as the short distance dispersers prefer young over old flowers.

Besides being an example of information use for making dispersal decisions, we show how passive dispersers may realize directed and long distance dispersal. Furthermore, our study highlights the benefits of combining field work and individual-based modelling or theoretical approaches in general.

 

Here is an interesting essay about measuring top-down-bottom-up effects, written by Leonard Polishchuk. He is also the first author of the Early View paper “How to measure top–down vs bottom–up effects: a new population metric and its calibration on Daphnia“, on which the essay is based.

Arguably, one of the saddest fallacies in ecology is the concept that «Everything is connected to everything else» (known as the first Barry Commoner law of ecology). The key assumption underlying this concept is that all interactions within the system are equally strong. Let’s examine which kind of science this assumption implies. Even in a modest system of 10 species the number of pair interactions between species amounts to 55 (including the effect of a species on itself), and to 5050 for a system of 100 species, leaving aside interactions with the abiotic environment. Such a large number is too big to study the interactions on a one-by-one basis, but probably too small to completely ignore their individuality. The latter is possible if the number of interacting entities is on the order of 10²³, the Avogadro constant, but this will lead us to the realm of statistical physics rather than ecology. The Commoner law, if correct, would make our attempts to understand Nature almost hopeless, and turn ecology into hardly more than a casebook of idiosyncratic examples. Or, following Ernest Rutherford’s famous dichotomy, ecology would have been close to stamp collecting rather than hard science. (Rutherford actually said “physics” and was basically right, because physics is a role model for genuine science. But we do not think that “physics envy” can really motivate the ecologist.)

The picture is not all gloom, however. Rather than falling into despondency, one could quantify species interactions in order to see whether they are of the same strength or not. The actual problem, as it often happens, is therefore an operational one; it is about how to measure the things of interest. Let us focus our attention on trophic interactions, that is, on bottom-up and top-down effects. One way to assess them dates back to Justus von Liebig and consists of addition of biological nutrients to see which of them elicit a strong response from the pot plant, in terms of its growth, or from the planktonic algae in a water sample, in terms of primary production. These simple experiments, which in the era of ANOVA are called factorial-design experiments, immediately disprove the Commoner law. Liebig’s law of the minimum states that there is a single factor that produces the biggest response in a given species or a set of species with similar requirements, and thus affects them most strongly. Hence, not only the interactions are different in their strength but, under any given circumstances, there is only one that is most important. Clearly, the Liebig law makes a contrast with the Commoner law.

While the factorial-design experiment is a powerful and efficient tool to reduce the number of significant interactions and detect the strongest one, it has its shortcomings. The imposed shifts in food and/or predator abundance, while not completely arbitrary, may not reflect the current situation in the system. Often, for example, one of the treatments completely excludes predators, despite their presence in the environment. In his 2001 review, Mark Hunter sarcastically notes that if we were to completely exclude food, this would have inevitably revealed an “obvious and dramatic bottom-up effect”. Of course, nobody would act that way in regard to food but this reductio-ad-absurdum example shows a general problem: the manipulative (addition / removal) approach does take into account the actual (rather than imposed) dynamics observed in the system. The dynamics is a fundamental feature of natural systems (Pimm 1991), implying that one driving factor, e.g. food, may be quickly replaced by another, e.g. predation, in the course of time and space. The factorial-design experiment is not tuned to track these changes while a truly dynamic approach might be able to make it.

These considerations naturally bring us to the field of population dynamics. In the paper, we have focused on zooplankton, in particular Daphnia, a well-known model organism in ecology (Lampert 2011, see Figure), though we do believe that our approach is a general one and may not be limited to zooplankton. The population characteristic we are dealing with is birth rate. In part, this is because planktonologists can take advantage of the Edmondson-Paloheimo model for birth rate. Interestingly, birth rate as a response variable is somewhat similar to growth or production rates often taken as response variable in manipulation experiments, but our use of it is different. The Edmondson-Paloheimo model, being slightly modified (Polishchuk 1995), relates birth rate to fecundity and proportion of adults in the population. Fecundity is closely associated with food conditions and proportion of adults with size-selective predation, the latter being common in zooplankton. Thus, birth rate depends on both bottom-up and top-down effects, which is another reason why it is used here. To quantify the role of fecundity and hence bottom-up effects and that of proportion of adults and hence top-down effects in birth rate dynamics, we employ a mathematical approach called contribution analysis (Caswell 1989, Polishchuk 1995, 1999, Polishchuk and Vijverberg 2005, Hairston et al. 2005, Ellner et al. 2011). This provides us with the ratio of contributions of changes in the proportion of adults and fecundity to birth rate change taken as a measure of the relative strength of top-down vs. bottom-up effects.

We view the ratio of contributions as a kind of measuring instrument, something like a thermometer. The comparison of the ecological instrument to the physical one is, of course, a metaphor – primarily because ecological variables do not obey simple and general quantitative relations such as those used to construct physical instruments; an example is the relation describing the thermal expansion of the physical body, which underlies the functioning of the thermometer. But it is a useful metaphor, for it leads to the next task: calibrating the ratio of contributions as a tool to measure the strength of top-down vs. bottom-up effects. This calibration is based on microcosm and computer experiments, and constitutes a major part of the paper. The main experimental result is that the ratio of contributions allows one to distinguish a strong top-down effect from a strong bottom-up effect.

In the end, we would like to emphasize some points not mentioned in the paper. First, while our approach focuses on population dynamics and, as such, is intended to avoid inappropriate averaging (used, though implicitly, in manipulative experiments), some time-averaging seems necessary. The ratio of contributions is found to be sufficiently robust only when applied to a set of successive sampling intervals rather than an individual interval. (This set covers the second part of the experiments where top-down and bottom-up effects appeared in full strength; see Online Appendix 3 of the paper.) In our experiments, this set was identified by means of ANOVA, the procedure that will not apply to field populations due to lack of “replicate populations”. Hence, we need to understand how to recognize, in natural populations, a set of intervals over which the ratio of contributions remains roughly constant. This will open the way to the use of this approach for natural Daphnia (and other zooplankton) populations.

Second, the Edmondson-Paloheimo model, when appropriately modified, has the potential to estimate birth rate in animals other than Daphnia, such as mammals. If applied to a wider range of organisms, this approach may be a useful supplement to conventional Liebig-style factorial-design experiments.

In the new Early View paper “Non-trophic effects of litter reduce ant predation and determine caterpillar survival and distribution”, Richard Karban and co-workers have studied the importance of litter for caterpillars hiding from ants in a hetergenous landscape. Here is Richard’s lay summery of the paper:

It is well established that trophic interactions can influence the spatial distribution and abundance of organisms.  What is less well understood is how these interactions vary across space.  In this study, we conducted several observational surveys and manipulative field experiments to examine the role of predators as drivers of caterpillar abundance and distribution across a heterogeneous landscape composed of three predominant habitat types, marsh, coastal grassland, and dune.  Unexpectedly, ants were found to readily prey upon early instar caterpillars.  The intensity of predation varied across habitat types such that caterpillars in marsh habitat had a higher probability of survival than those in drier, upland habitat. Marsh habitat in our study system is characterized by think leaf litter, while less leaf litter is associated with drier habitat.  We hypothesized that habitat substrate complexity may moderate caterpillar predation by ants. This hypothesis was supported by two findings: ant recruitment to baits decreased with litter depth and litter protected caterpillars when ants were present but not when ants were experimentally excluded. Our results show that litter confers a survival advantage to caterpillars by providing habitat, a non-trophic mechanism. In contrast to trophic effects, the importance of spatiotemporal variation of non-trophic effects in mediating species interactions has been underappreciated by many ecologists.

How the anadromous fish alewife affect the whole food-web in it’s ecosystem is studied by Jerome J. Weis and David M. Post in their new Early View paper “Intraspecific variation in a predator drives cascading variation in primary producer community composition”. Below is Jerome’s presentation of the paper:

We know that predation can have a strong influence on the richness, biomass, and composition of prey communities.  We also know that these effects can cascade down a food web to lower trophic levels, including primary producers.  Often, when we design studies to ask how these top-down effects of predators influence lower trophic levels, we focus either on differing densities of a single predator species, or on differences among multiple species.  However, in some cases, variation within a predator species can be an important component of these top-down effects.

In coastal New England lakes, a species of zooplanktivorous fish, alewife, has a strong influence on zooplankton biomass, diversity, and composition.  Among lakes that support alewife, populations show one of two distinct life histories, an anadromous life history, where ocean residing adults spawn in coastal lakes and young-of-the-year alewife have a substantial impact on zooplankton communities from approximately June until November, and a landlocked life history, where alewife populations are isolated from the ocean and are present through the year.  Differences in the behavior, morphology, and seasonal timing between anadromous and landlocked alewife drive distinct differences in their zooplankton prey communities across the landscape.

In this study we tested the hypothesis that alewife presence and life history will have cascading top-down impacts on phytoplankton density and community composition. We analyzed phytoplankton communities from a mesocosm experiment that manipulated the presence and life history form of alewife and observed lower zooplankton biomass density, average size, and species richness in the anadromous treatment than the landlocked and no-fish treatments.

We observed a statistically significant shift in phytoplankton community composition among treatments that was consistent with lower zooplankton densities in the anadromous alewife treatment.  The biovolume density of two common single-celled phytoplankton genera, Chlamydomonas and Gymnodinium, was significantly higher in the anadromous treatment than the landlocked and no-fish treatments.  Both of these genera are considered vulnerable to herbivory by zooplankton.  However, these differences in community composition did not result in statistically significant differences in overall phytoplankton biovolume density nor richness among treatments, suggesting that the cascading effect of alewife was relatively small in this study.

A model to quantify species interactions is proposed in the new Early View paper “Costs, benefits, and loss of vertically transmitted symbionts affect host population dynamics” by Kelsey M. Yule, Tom E.X. Miller and Jennifer A. Rudgers. Below is Kelsey’s background story to the study:

How do we quantify the relationship between two species? When individuals of the two species interact at many points throughout their lifetime, the answer is not as simple as we sometimes assume.  The effect of the interaction at different points in the species’ life history may not affect fitness in the same way. Take, for example, an insect pollinator that greatly increases the reproductive success of its plant partner. We might consider this a classic example of a mutualism, as the presence of the pollinator allows the plant to produce more seeds and the presence of the plant allows the pollinator to produce more eggs.  However, that same pollinator may lay those eggs directly onto the plant, which later suffers significant herbivory damage from the larvae. So, which plant produces more offspring: the one that interacts with that particular pollinator or the one that doesn’t? Without following the plants’ growth, reproduction and survival throughout their lifetimes, it’s difficult to say. Even humans harbor many symbionts of which the varying positive and negative effects are only recently beginning to be understood and debated.  This tension between cooperation and conflict is not uncommon in many of the systems we traditionally call mutualisms or parasitisms. In our paper, we argue that a snapshot at one point in the life history is not sufficient for understanding the population-level effects or evolutionary significance of any interspecific interaction.

Fungal endophytes that produce herbivore-deterring alkaloids are generally considered clear mutualistic partners of their grass hosts in agronomic systems.  Yet, confusion and debate over their role in native systems has arisen due to some documented costs, notably reduction in host survival.  Theory suggests that when these endophytes are vertically transmitted, harming their hosts should doom them to extinction, as the endophytes can only increase their own reproduction by increasing their hosts’ reproduction.  Yet, vertically transmitted endophytes are often present at high frequencies in native systems, despite transmission rates that can be well under 100%. Therefore, we wondered whether an approach that could integrate the effect of endophytes across the entire life history of the host could shed some light on this problem.

To do this, we developed a new modeling approach in which we could structure a native grass host’s population both continuously by size and discretely by the presence or absence of endophyte symbionts.  With our integral projection model (IPM) megamatrix, which we parameterized with experimental field data, we were able to show that endophyte symbiosis provided a net benefit to its host by increasing population growth. Indeed, we saw costs to host survival that were outweighed by boosts to growth and reproduction.

More surprisingly, we saw some patterns that we did not expect given previous theory. Early life history stages, like germination and seedling establishment, were critically important for determining the locations of transmission rate thresholds below which these beneficial symbionts go extinct.  For example, if seedlings are able to survive to adulthood 2% of the time, endophytes will not be able to persist if endophyte symbiotic adults produce endophyte symbiotic seeds, as opposed to endophtye-free seeds, less than 50% of the time. However, if seedlings establish 3% of the time, endophyte persistence requires a transmission rate of more than about 75%.  This complex interaction between early life history and vertical transmission arises because higher seedling establishment leads to a greater proportion of the population being made up with seedlings, which will be dominated by endophyte-free plants at low transmission rates. This result also highlights the need for a greater understanding of the mechanisms behind variation in endophyte transmission.

We believe that the modeling approach we developed will be broadly applicable to understanding how species interactions, especially those involving vertically transmitted symbionts, influence populations.  For myself, this research, which I began as an undergraduate, is influencing my thoughts on species interactions as I start my graduate career at the University of Arizona.  In the future, I hope to continue integrating models with empirical data. I believe that doing so is a  particularly powerful way to improve our understanding of relationships in nature that so often slide on the continuum between mutualism and parasitism.

Did you believe that hermite crabs were always seeking lonelyness? Oh, now, partytime might attract the hermits as well! Read more in the new Early View paper “Eavesdropping foragers use level of collective commotion as public information to target high quality patches” by Mark Laidre. Here is Mark’s own short verison of the paper:

Many people like a party that’s pumping and jostling at just the right amount. Too little commotion and it’s just not attractive. The same seems to hold for terrestrial hermit crabs, which are highly social animals that frequently join aggregations of conspecifics to acquire valuable resources like food or shells. We conducted an experiment to determine what level of commotion from an aggregation would be most attractive to crabs that were eavesdropping outside the aggregation and deciding whether or not to join. The experiment involved creating the equivalent of a puppet show for hermit crabs, with several plugged shells being jiggled at the end of fishing line to simulate different levels of jostling by an aggregation. The jostling of these sham aggregations represented the sort of wild commotion and fighting that goes on when hermit crabs are competing with one another naturally. Indeed, when hermit crabs are contesting highly-quality food resources or when they are in the process of evicting another individual from its shell, their aggregations exhibit especially high levels of natural jostling. In our experiment, we found that eavesdropping hermit crabs were most attracted to the sham aggregations that were jostled at higher rather than lower levels, suggesting that the crabs were using the raucous public commotion as a reliable cue to the presence of valuable resources that were worth competing over. Our experiments provide the first evidence that animals use the behavioral by-products of collectives as a way to increase their own personal foraging efficiency.

Pollution issues meet complex food-web modelling and theoretical ecology in the Early View paper “The more polluted the environment, the more important biodiversity is for food web stability”, by Leslie Garay-Narvaez, Matias Arim, José D. Flores and Rodrigo Ramos-Jiliberto.

Here’s the background story to the study, written by Rodrigo Ramos-Jiliberto:

I was the advisor (together with M. Arim) of Leslie Garay-Narváez, who recently obtained her PhD degree at the University of Chile. This article is the first chapter of her PhD dissertation. When we began to think about possible alternatives for her thesis work, Leslie decided to combine a theoretical approach for studying the dynamics of food webs, with questions related to the effect of human disturbances, particularly pollution. Our desire was to connect very abstract work, based on mathematical modeling and complex networks, with practical needs of social interest. Thus, we decided to go in the direction of revising or perhaps reformulating some key issues of ecological theory, which had been building (explicitly or implicitly) with a pristine world in mind, but considering a polluted world. We envisioned developing some sort of “applied theoretical ecology of polluted complex systems”. In this article we show how the complexity-stability relationship is affected by pollution. Two other papers are in the pipeline.

As a result of Leslie’s work, our institution, the National Center for Environment (CENMA), appreciated the importance of theoretical ecology, and many members of our academic community agreed in that applied questions are affordable from a sound, theoretical perspective. After that, three months ago, Leslie became a happy mother of a baby and obtained a 3-year postdoc fellowship at the University of Chile. Indeed in developing countries like ours, science is a fine form of living, and theoretical ecology even better !

Read David Choquenot’s and David M. Forsyth’s new Early View paper “Exploitation ecosystems and trophic cascades in non-equilibrium systems: pasture – red kangaroo – dingo interactions in arid Australia” to learn more!

Here’s Dave’s background story to the study:

This article had a long gestation. The seeds were sown in 2000, when two influential articles were published in The American Naturalist on the inter-related topics of trophic cascades (Schmitz et al. 2000 Am. Nat. 155, 141) and the Exploitation Ecosystems Hypothesis (EEH; Oksanen and Oksanen 2000 Am. Nat. 155, 703). After reading these articles we discussed the idea of adding the dingo (the top-order predator in mainland Australia) to Graeme Caughley’s two-link rainfall – pasture – red kangaroo model (Caughley & Gunn 1993 Oikos 67, 47), to test whether an empirically derived model could recreate EEH predictions and generate trophic cascades. In Caughley’s system, which was based on data collected in Kinchega National Park (western NSW; Image 1), prevailing productivity is tightly linked to rainfall through its effect on pasture growth and dieback. However, rainfall in this ecosystem is highly stochastic between seasons and years. Over the subsequent ten years we worked sporadically to test whether this system could produce dynamics consistent with the EEH and trophic cascades.

The model did reproduce the three zones predicted by the EEH, but a surprising outcome was the discovery of an additional zone at productivities above which the maximum densities of the dingo was achieved. The additional zone, in which kangaroo densities increased and pasture biomass declined due to the re-engagement of the kangaroo-pasture feedback loop, occurred because dingo densities are believed to be socially regulated (via dominant female infanticide): if dingo densities are instead constrained wholly by the availability of kangaroos then that zone disappears, kangaroos become less abundant and pasture biomass more abundant.

Increasing stochasticity in seasonal rainfall had sometimes counter-intuitive effects on model outcomes. High levels of stochasticty led to more frequent extinction of dingoes from the system, resulting in the re-engagement of the kangaroo-pasture feedback loops. Hence, increasing stochasticity led to increased attenuation in this system.

Roger Pech (Landcare Research, New Zealand) thoughtfully suggested that we use the normalized difference (rather than the absolute difference) of the log-response ratios to evaluate attenuation in this system. Roger’s suggestion will be appropriate to other studies assessing attenuation in trophic cascades.

Several journal reviewers also suggested that we assess the effects of potential diet switching by dingoes from kangaroos to reptiles, as has been observed in some areas of arid Australia. We found that prey switching by dingoes to reptiles weakened trophic cascades.

The role of the dingo as a trophic regulator has been the subject of much recent debate, with some scientists calling for culling to cease and reintroductions to be made in areas where it has been extirpated. The rationale for returning dingoes to previous densities in parts of their range focuses primarily on their potential to reduce the abundance of introduced red foxes and feral cats. However, our study suggests that additional benefits may occur through regulation of large kangaroo abundance, and the associated release of vegetation from grazing pressure. Depending on the degree to which the diversity of each trophic level is maintained by consumption-mediated co-existence, these changes may have flow on implications for amongst herbivores and vegetation biodiversity in these ecosystems.

Our study has generated testable predictions about interactions between top-order carnivores, their prey, and vegetation across productivity gradients. These predictions are obviously highly testable in Australia where dingo management is widespread. However, the generality of the predictions could also be tested in entirely different predator-driven ecosystems.

What makes invasive species invasive? Find some of the answers in Rafael Zennis and Martin Nunez paper “The elephant in the room: the role of failed invasions in understanding invasion biology”  now on Early View.

Here, Martin Nunez gives a short background:

Invasive species grow bigger, reproduce earlier and more often, and spread faster than other species, right? Well, sometimes yes, but not always. Many known invasive species have populations introduced in areas where they do not naturalize or invade after arrival. As it turns out, only invasive populations exist in nature. In this study, we reviewed the literature on invasions and found that failures are the most numerous and often ignored part of the biological invasion process. We learned that very few people are interested in introduced populations that do not thrive in the new environment. There are many anecdotal reports on failures, but really few studies on why these populations fail. We also found that different mechanisms may be causing failures vs. successes, but more research is needed to shed light on this. Based on these findings, we show and discuss research areas where it may be key to incorporate more info on failures to avoid an important bias.

Maritine pines (Pinus pinaster) are invasive in many parts of the southern hemisphere, but in Rio Negro, Brazil, experimental plantations died out 18 years after planting leaving no trace of its past presence in the area, now colonized by exotic eucalyptus and native araucaria pines.

We focused our study on reviewing cases of species that are invasive somewhere, but that fail to invade in other areas, habitats or time periods. We did this because these situations can provide useful information on the particular mechanism of invasion (e.g., what is different between areas where the species invade and where the species does not invade?). We avoided studying species that never invaded, which might provide little information about other invasive species.  Finally, we put caution in the use of the term “invasive” to indicate an intrinsic species-level trait because even some of the most aggressive invaders are reportedly unable to colonize some area. This does not change, however, the fact that when introduced organisms do invade, they may cause considerable changes in community and ecosystem dynamics.

Do animals spend too much energy on just being? Read Bas Kooijman’s new Early View paper “Waste to hurry: dynamic energy budgets explain the need of wasting to fully exploit blooming resources” to find out! Here, Bas gives you the background to the study:

Many years ago, I did a very simple experiment, which results puzzled me for a long time. Take 6 beakers, fill them with water, add 5 daphnids each, and feed them with algae daily. The beakers got 6, 12, 30, 60, 120 and 240 million cells per day, respectively, for 24 days. Except for the highest feeding level, all daphnid populations settled to constant numbers per beaker in this period and the numbers are directly proportional to the feeding levels. To convince myself that it really is the feeding level that controls the numbers, I gave all beakers 30 million cells per day after 24 days and indeed all numbers converged to that level. From this we learn that a 2.8 mm daphnid needs 6 algal cells per second at 20°C and they cannot grow or reproduce with this intake and all need it for maintenance only. With plenty of food they can become over 4 mm and produce some 20 young per day. It turns out that they have a specific maintenance cost that is two orders of magnitude bigger than is typical for animals. My problem was to understand why.

Some two years ago, I started the add_my_pet collection of data on animal energetics, and fitted the standard Dynamic Energy Budget model to each species. These data and the model cover all aspects of energy and mass balances during the full life cycle of individuals, including the embryo stage. The collection has representative of most larger animal phyla, ranging from 2.4e-8 g hairy-backs to  1.6e8 g blue whales. I developed this model to separate overhead costs of assimilation, growth and reproduction from maintenance. Because of the presence of reserve as quantifier for metabolic memory, this task is less easy than is generally recognized. In fact, it requires a whole new view on the relationships between respiration, metabolic rate and maintenance. With help of many enthousiastic people, the add_my_pet collection grew till 165 species at present.

By comparing extremes in specific maintenance costs I found the explanation for the very high maintenance costs of daphnids and for why it took me that long to see it. It is namely completely counter-intuitive: animals need to waste resources to boost their growth and reproduction. Within the context of the Dynamic Energy Budget theory, it is completely logical and easy to understand, the only problem is to recognise it. It has been sitting right before me for 30 years and I didn’t see it. Intuition is not always a good advisor.

Editor in Chief Prof. Dries Bonte introduces the two Editor’s choice papers in the February Issue: (Note that Editor’s choice papers are Open Access)

For the February issue of Oikos, we decided to highlight Sorte’s forum paper on the importance of flow direction and limitation to redistribution for the persistence of species in the light of climate change, and the contribution of Stier et al., demonstrating the use of model-based approaches to study functional predator-prey responses within a community context. These contributions were chosen according to our motto of synthesising ecology.

Sorte (2013) emphases the role of directional flows of wind or water currents as an important factor limiting species’ distributions, especially when equilibrium conditions become disrupted by human interference. There is a consensus that adaptation or tolerance may not be sufficient for many species to persist under conditions of climate change, and that dispersal is essential to keep track with the shifting climate window. In cases of actively moving organisms, such movements can be expected to be informed and at least partly in the direction of the shifting window. Passively dispersing organisms, being either wind dispersed plants, rafting arthropods or planktonic stages of many marine vertebrates and invertebrates are expected to face constrained movements due to their dependency on flow directions. Such asymmetric air and water flows need to be considered when assessing the vulnerability of populations and species to climate change. Cascade Sorte provides a synthesis on how the interplay between directional flows and life histories may limit species’ distributions and their persistence under climate change. The review comes up with clear predictions that may help ecologists to detect the set of passively dispersing species at risk, but equally provides clear considerations for future research.

Adrian Stier and colleagues provide a novel analytical tool for analysing predator foraging behaviour and offer insight into the processes driving the dynamics of coral reef fish. While group benefits are well documented from a single-species point of view, we lack insights on how such group benefits change according to the community context. In their study, the authors use a shoaling coral reef fish as a model species to test how prey group benefits change according to group size, the presence of competing predators and alternative prey. They use an original approach by quantifying mortality rates as perceived from the predator’s perspective, so by quantifying changes in the predator’s functional response. Their sets of experiments confirm group size advantages by reduced predation risks, but these benefits decrease in the presence of alternative prey species. While there is already quite some literature demonstrating such a community context of predator-prey interactions, the applied model-based approach allowed for testing several alternative hypotheses of mechanisms leading to variation in functional responses.

We have now come to the second Surf and turf paper in Oikos february issue. I let Deron Burkepile introduce you to his study “Comparing aquatic and terrestrial grazing ecosystems: is the grass really greener?”

At a big ecology meeting, you can often tell what people study by how they dress – the marine ecologists (Hawaiian shirts, flip flops), the terrestrial ecologists (Chacos or Tevas, Carharts). As an ecologist, the communities and ecosystems you study often define you – forest ecologist, intertidal ecologist, benthic ecologist. Like our current series of reviews and commentaries in Oikos trying to bridge the gaps among terrestrial, marine, and freshwater ecology, we often compare and contrast the different patterns and process in our different ecosystems via reviews and our meta-analyses. We search for common patterns and themes and build testable hypotheses, even theories. Yet, many of us don’t have research experience outside of a couple of closely related ecosystems. For many of us, branching out to a new ecosystem means including tropical forests into our research program on temperate forests. But, I would argue that we could all be better ecologists, if we truly had diverse research experiences on our ecological resumes, and the field would be better for it.

Having had a diversity of research experience, I feel like I am one of the lucky ones. I’ve spent more than a decade studying coral reefs, even lived underwater for a total of twenty days in the Aquarius, an undersea research station off of Key Largo, Florida to study herbivorous fishes (parrotfishes and surgeonfishes) and their importance to reef ecosystems. But, I also got to spend two years living in a tent in Kruger National Park in South Africa (periodically having to put my computer in the refrigerator to keep it from overheating in the 40°C+ heat). Instead of parrotfish and surgeonfish, I was studying elephants, wildebeest, and impala and how these different herbivores structured savanna ecosystems. While the beasts were different, the ecological processes were not. I like to think I’m the only ecologist who has gotten to live and work both in the bush in Africa and also underwater (if you know otherwise, please don’t burst my bubble).

How did I get from coral reefs to African savannas and back? It all started with reading broadly. While studying for my qualifying exams as a graduate student in coral reef ecology, I came across the classic papers on the Serengeti by Sam McNaughton and the book Serengeti: Dynamics of an Ecosystem by Sinclair and Norton-Griffiths. I was enthralled reading about wildebeest migrations, the dynamics of multiple large predators, and the overwhelming impact of herbivores on the landscape. As I was devouring the coral reef ecology literature, I couldn’t help thinking how similar coral reefs and African savannas actually were. Instead of herds of wildebeest there were schools of parrotfish. Instead of roving impala, there were marauding urchins. Regardless of whether the system was wet or dry, big, diverse groups of herbivores ran the show. I was fixated on how cool it would be to test similar hypotheses about how diverse groups of herbivores impact community structure and ecosystem function in two structurally different, but functionally similar ecosystems.

After convincing my future post-doc advisor, terrestrial ecologist Melinda Smith, that it would be a good idea to let a marine ecologist who had never even been to the African continent to go live in a tent in South Africa and study ungulates, it was mostly downhill from there. Of course I had to learn a brand new ecosystem (dry vs. wet), a new set of taxonomy (grasses vs. seaweeds), a new set of dangers (lions vs. sharks), get used to new field methods (see picture as exhibit A), and learn a new set of literature (fun, and probably the most challenging part). There are clearly concepts that don’t cross these ecosystem boundaries. The effects of drought and water stress are extremely important at our sites in the savanna – on a coral reef, not so much of a problem. But after six years of working in both African and North American savannas while also continuing my work in reef systems (yes I have a lot of frequent flyer miles), I’ve been able to build a much more nuanced and thorough understanding of how herbivores shape ecosystems and of the drivers that determine herbivory.

So I encourage ecologists at all levels (especially ones early in their careers) not just to read broadly but to research broadly. Start a collaboration with someone in a very different ecosystem than your primary research. If you work in forests, go talk to someone about kelps. It will push your intellectual boundaries and stimulate more ideas to tackle in your primary research area. Every aspect of your career will likely benefit, from your lectures to your journal reviews to your grants.

I remember in my first few months in South Africa walking through an area of savanna where an African buffalo herd had been the day before. The soils were churned, the small shrubs mangled, the grasses gnawed. But what I remember most was the amount of dung. Buffalo flops everywhere. I distinctly remember thinking how important these big herds must be for moving nutrients around the landscape and impacting primary production. That same scene came to mind a couple of years ago while diving on a coral reef watching big schools of fish congregate around corals. That same thought then popped into my head – how important these fish must be for moving nutrients around within this landscape. So, now one of my lab’s main areas of research is the impact of fish-derived nutrients on coral reef community structure and ecosystem function. My blended heritage of marine and terrestrial ecology will, hopefully, continue to help me unravel the connections and common themes between wet and dry ecosystems. Even now, when I am following a parrotfish around the reef documenting its feeding behavior, I can’t help but think “What would a rhino be doing?”

An NCEAS working group examining the future of publishing in ecology and evolutionary biology (http://www.nceas.ucsb.edu/projects/12651) would like to solicit your input. Our goal is to establish a baseline of your opinions on the current state of scholarly communication for our field so as to highlight potential gaps and improvements. The survey includes the opportunity to provide feedback on the value of Twitter, blogging, social networking, and other online outlets as it relates to publications.

The survey will take approximately 7-10 minutes.

http://bit.ly/eebpublishing

Yesterday, Randi Rotjan and Josh Idjadi introduced us to the Surf and Turf concept. Today, Howard V. Cornell gives a short background to his and Susan P. Harrison’s Surf and Turf paper “Regional effects as important determinants of local diversity in both marine and terrestrial systems”:

When Josh Idjadi and Randi Rotjan organized the Surf and Turf Symposium at the 2009 meeting of the Ecological Society of America, it was immediately clear that they had identified an important problem. Marine and terrestrial ecologists do not always follow each others’ work, and as a result, there is not enough cross-fertilization of ideas derived from the study of these two realms. When Josh and Randi invited Susan Harrison and me to participate in the symposium, it forced us to think hard about how large-scale biogeographic  and evolutionary processes affect the species diversity in marine vs. terrestrial communities. Because of differences in dispersal between atmospheric and aquatic media, the ease of identifying marine vs. terrestrial species pools, and the historical development of marine and terrestrial community ecology, marine ecologists have placed more emphasis on the importance of large-scale effects on community structure than terrestrial ecologists. Nevertheless, it became clear to us upon reflection that large-scale processes are important in both realms but such processes are studied in different ways. We were grateful for the opportunity afforded by the symposium to look at this issue more deeply and as a result, have come to a clearer understanding of the general importance of examining different spatial scales when trying to understand ecological patterns. Below is a short summary of our paper.

One apparent difference between marine and terrestrial ecology is that the influence of regional processes on local populations and communities is better established in the marine literature. We examine three potential explanations: 1) influential early studies emphasized local interactions in terrestrial communities and regional dispersal in marine communities. 2) regional-scale processes are actually more important in marine than in terrestrial communities. 3) recruitment from a regional species pool is easier to study in marine than terrestrial communities. We conclude that these are interrelated, but that the second and especially the third explanations are more important than the first. We also conclude that in both marine and terrestrial systems, there are ways to improve our understanding of regional influences on local community diversity. In particular, we advocate examining local vs. regional diversity relationships at localities within environmentally similar regions that differ in their diversity either because of their sizes or their varying degrees of isolation from a species source.

Figure: Scenarios for propagule supply in marine and terrestrial systems. (a) In marine systems, habitats are immersed in a homogeneous surrounding medium containing propagules of many species with few dispersal barriers, many of which pass through the fitness filter and are able to recruit to the habitat. (b) In terrestrial systems, topography and environmental heterogeneity erect larger dispersal and fitness barriers to arriving propagules and ‘seed banks’, confound arriving propagules with those already present in the habitat.

Check out the Surf & Turf papers in the February Issue! For an introduction to the concept, I leave the word to our Surf and Turf editors Josh Idjadi and Randi Rotjan. Their introductory paper in the February Issue is found here. Presentations of the actual papers are to come on this blog the following days!

It is an interesting time to be a scientist. We have access to more research tools and information than ever before, including literature access. With that access comes great opportunity: data mining, meta-analysis, global comparisons and insights, and cross-disciplinary and cross-system inspiration. However, this tremendous level of access also opens up the conversation about responsibility: are we responsible for reading that huge literature? The answer is, by necessity, “of course not”.  But like everything in science and in life, this is not a black and white issue. Among the many shades of gray are whether or not you have the responsibility to read everything in your field (traditionally, “yes”), but defining ‘your field’ is ever-harder. Is your field defined by the organism you work on? By the ecosystem you work in? By the methodology you use? By the types of questions you try to answer? The answer is “all of the above, depending on the situation”. Practically, however, it would be impossible to read and absorb information on all of these levels, in real time, all of the time. Not only do we have more access to information, but there is more information! More scientists, more journals, more articles, and more communication mediums (including blogs, like this one). In reality, we all simply do the best we can, all-the-while recognizing the importance of deep and wide reading to good scholarship.

Recently, in a rare moment of quiet and clarity, we realized that our worlds had become very “marine”. Though we both graduated from more traditional and cross-system biology departments and considered ourselves ecologists, in reality, we were working in marine systems, attending marine conferences, and immersed in marine literature. We missed being part of the general biological scene, and we wanted to engage in the scholarly exercise of thinking about some of our research questions from the perspective of a different field.  “Surf and Turf” emerged as a concept – not to wholly solve the problem – but as one part of the solution to service cross-systems cravings in a way that would be relatively short, with a reasonable time investment, and would engage collaborators in a meaningful discourse without diluting point-of-view by trying to reach consensus in a single document. We thought an effective format for this concept might be a main piece on a topic by a system-specific author, with short responses written by other system-specific authors. In this multi-paper-per-topic dialogue, the goal was to achieve breadth without compromising depth in a format that didn’t swamp an individual author by forcing an all-systems literature review, and in a way that didn’t swamp the already overwhelmed reader who is forever trying to keep up with their own field (however it may be defined).

Our authors found both agreement and debate in the 2 topics highlighted by Oikos (regional determinants of diversity, and grazing ecology), and we hope this virtual issue showcases these 2 topics as proof-of-concept examples for future Surf and Turf endeavors. In the process of putting this virtual issue together, we engaged with a number of other authors who are pursuing other venues for several additional topics. Oikos was a wonderful place to launch this concept – and we are now hoping that other journals and authors will embrace it. Still immersed in our system-specific questions, we both value and recognize the importance of cross-systems ecology as one of the key drivers of synthesis. This will not be our last attempt at cross-systems thinking, and we encourage you to do the same.  And at the least, and in this cluttered world of fast-flowing literature: thank you for reading.

-Randi Rotjan & Josh Idjadi

What do animals actually do in poor environments? Compete more or facilitate for each other? Isabel Barrio and her co-workers studied this in herbivores in the harsh alpine tundra, resulting in teh new Early View paper: Extending the stress-gradient hypothesis – is competition among animals less common in harsh environments? Here’s Isabel’s own background story to the study:

Many summers in the alpine tundra have inspired our study.  Alpine environments are strongly seasonal and are characterized by harsh environmental conditions, but they can host a surprisingly large numbers of herbivores.  Annual net primary productivity in alpine ecosystems is generally low, so negative interactions (i.e. competition for resources) are usually expected to dominate among herbivores.  However, the stress gradient hypothesis (SGH) developed by plant ecologists leads to the opposite prediction; namely, that in stressful environments, positive interactions (i.e. facilitation) would be the most common type of interaction.  But, are plants and animals so different in this respect?  Although facilitation among animals has been described in some highly productive ecosystems, such as tropical savannas, no theoretical framework exists that relates the balance between positive and negative interactions along environmental gradients.  In our paper “Extending the stress-gradient hypothesis – is competition among animals less common in harsh environments?” we evaluate how the stress-gradient hypothesis might apply to terrestrial herbivores.  

We considered  alpine herbivores for developing our framework, because most examples of the SGH come from alpine plant communities.  According to the SGH, and given that stress for herbivorous animals in these environments can be equated to inverse productivity gradients, we wondered if positive interactions would prevail in alpine environments because of their low productivity.  We reviewed the available examples on interactions among alpine herbivores and found very few experimental studies on this topic.  Interestingly, they were biased towards reporting on significant competitive interactions.  Despite this bias, we found no evidence of competition being the dominant interaction type in low productivity alpine environments, which directly challenges the dominant view among animal ecologists.  Although we did not find strong support for the SGH either, we argue that specifically designed experiments can help investigate the applicability of this framework to terrestrial vertebrates.  Extending the SGH through clear predictions can provide a solid starting point for understanding the role of positive and negative interactions in structuring terrestrial animal communities.

From January 2013 our Editor’s in Chief select two papers in each issue as Editor’s Choice. Those papers are Open Access, and the complete January Issue is OA! Here, Dries Bonte explains why they chose the following for the January issue. Read more here about News in Oikos 2013.

The following papers ‘Pattern Detection in Null Model Analysis’ (Werner Ulrich and Nicholas J. Gotelli) and ‘How does the invasive/native nature of species influence tadpoles’ plastic responses to predators’ (Eudald Pujol-Buxó, Olatz San Sebastián, Núria Garriga and Gustavo A. Llorente)were selected as the first editor’s choice papers for 2013.

We selected these papers for two different reasons, thereby demonstrating the different pathways by which ecologists can create synthesis in their own field of expertise. The work by Pujol-Buxó considered the importance of phenotypic plasticity in both functional morphology and behaviour in a set of invasive and native prey and predators. The work brings synthesis by merging concepts of behavioural ecology, developmental plasticity and invasion ecology and provides a mechanistic understanding of invasions in a well selected set of species (interactions).  It is true that the ecological impacts of invasions are becoming well understood, often in the sense of impact on population and species dynamics of native species. However, since all changes in ecology should ultimately result in altered selection pressures and back, more effort is needed to understand eco-evolutionary dynamics of species invasions, both in the invasive and native species. This field becomes nowadays overwhelmed with theory and empirical work is clearly lagging behind, so contributions like this are essential as critical tests of the developed theory.

The second contributions Ulrich and Gotelli emphasises on the proper use of different metrics to identify distinctive patterns in species x site presence-absence matrices. These approaches are important for understanding metacommunity organisation. Because the behaviour of different metrics is often correlated, it proved to be difficult to distinguish different patterns. Therefore, Ulrich & Gotelli created synthesis by testing the performance of a suite of null models and metrics that have been proposed to measure patterns of segregation, aggregation, nestedness, coherence, and species turnover. While there is no need to provide more detail here, they concluded that sources of non-randomness are best assessed by using different combinations of metrics. As such the paper is a natural and logic continuation of their previously published and highly valued consumer’s guide to nestedness analysis. We are sure that this contribution will receive the same attention and use in future community ecology.

It’s always fun to read all submitted manuscripts. Especially when explanations are like this:

I’m very happy that it doesn’t happen too often!

This one was actually copied from  #overlyhonestmethods

Have a great weekend everyone!

How do wood decomposition relate to other traits in the tree? Answered by Benjamin G. Jackson and co-workers in the Early View paper “Are functional traits and litter decomposability coordinated across leaves, twigs, and wood? A test using temperate rainforest tree species”. Here’s Benjamin’s short summary and his pedagogic figure showing the results:

Dead wood represents an important pool of carbon and nutrients entering the decomposer subsystem in forested ecosystems. However, our understanding the factors regulating wood decomposition remain poorly characterized. In our study we ask two main questions:

1. Do tree species with leaves that decompose rapidly also have wood that decomposes rapidly?
2. Do the same functional traits that control leaf litter decomposition control the decomposition of wood?

We addressed these questions by comparing how traits and litter decomposition vary across 27 co-occurring tree species from temperate rain forests in New Zealand. For each tree species, we quantified the functional traits of their green leaves and leaf, twig and wood litter and then decomposed the three litter types under controlled conditions. Below we show how the main findings of our study fit into the broader picture emerging from recent research into plant functional traits and litter decomposition.

Oikos’ Editor in Chief, Prof. Dries Bonte, presents some interesting news and wishes you all a wonderful 2013:

A survey among readers revealed that Oikos is considered as a solid, high quality journal publishing broad ecological topics, often controversial papers and synthesising papers.  Synthesis in Ecology is already for long time our branding, but it is not always clear for readers and authors what is actually meant by that. For us, bringing synthesis is the only way to make serious advance in ecology. This can be achieved by merging different methodological, disciplinary, taxonomical or geographical aspects of ecology to create novel insights that move beyond providing the n-th case study on a certain ecological topic. While this rather confirmative research is intrinsically highly valuable, and inevitable to eventually create synthesis, Oikos will continue to prioritise the publication of the most novel, synthesising contributions. In a world flooded by scientific journals, such initiatives are essential to remain updated with the newest advances and insights in the field.

One new direction Oikos is heading for is the publication of meta-analyses as a separate section. Chris Lortie, our senior expert editor will be in charge of these incoming papers, evaluate proposals and invite original contributions. Dustin Marshall remains responsible for handling incoming Forum papers.

Authors publishing manuscripts that create synthesis –either meta-analyses, forum or regular papers- in Oikos will receive from 2013 onwards a real incentive, by providing fast publication, highlights of their work in the issue and social media, and open access. These papers will be highlighted as editor’s choice, and a box on the synthesis will be provided on each of these papers. In the near future, we will ask all authors to provide such a synthesis box at submission. When feasible, virtual issues centred on these synthesising contributions will be published.  In the near future, you can expect for instance such a guest-edited issue on Surf and Turf papers, and some more other exciting proposals have been received. More news on these will follow on our Facebook-page and on the Oikos-blog of course. On the other hand, Oikos will refrain from publishing rebuttal papers, but instead welcome balanced commentary papers that progress the field as a forum.

Oikos will further invest in the blog to show what Oikos is, communicate with readers, to serve authors with promotion of their papers. The base will be posts about papers in Early View that are provided by the authors. It could be photos, a background story to the study, a popular summary.  Essentially we seek for the blog answers on the following questions:  how did you get the idea, how long have you spent working on the project, any mistakes, why that species/system/field site etc.

As you can read, we do continue our investments to bring Oikos at the front in publishing the most exciting work in the field of ecology. We received about 1000 manuscripts in 2012 (of which we can print approximately 220 to keep the backlog rather limited). The editorial work is consequently only possible by having an extremely dynamics and motivated team, starting with the senior editors and 50+ handling editors that take fast and well-considered decisions on the incoming manuscripts, technical and managing editors processing all incoming and accepted papers, and of course, all our readers and authors that are engaged in the publication process by providing peer review of the highest quality. I truly thank you all for your work to support Oikos as a leading journal in ecology. My best wishes for 2013!!

Isn’t it just amazing how well adapted the tiny parasitic wasps are? Parasitoids want to lay their eggs in good, yummy caterpillars. Yummy caterpillars are those feeding on high quality plants. Quality of plants is partly determined by if their roots have been eaten by below ground herbivores. Plants smell differently above ground, depending on if their roots have been eaten or not. These odour variations are learned by the parasitic wasps when identifying the high quality hosts.

These results are presented in the new Early View paper “Effect of belowground herbivory on parasitoid associative learning of plant odours” by Marjolein Kruidhof and her co-workers. Here’s Marjolein’s own summary:

Only experienced parasitic wasps adapt their preference for plant odours in the presence of root feeders

Although hidden in the soil, insects that feed on plant roots often do not go unnoticed by insects living aboveground. Upon root feeding, the odour the plant emits into the air changes. Tiny parasitic wasps, which lay their eggs inside the body of host caterpillars that feed on the plant leaves, use these plant odours to locate their hosts. Researchers from the Netherlands Institute of Ecology (NIOO-KNAW) in the Netherlands tested whether two closely-related parasitic wasp species, Cotesia glomerata and C. rubecula, expressed a preference for plants with or without Delia radicum root feeders. As inexperienced wasps of both species did not respond to the presence of root feeders, they continued to investigate whether the parasitic wasps could develop a preference after gaining experience when parasitizing caterpillars on root-infested or root-uninfested plants. Indeed, both wasp species adapted their preference for plant odours to the presence of root feeders, but did so in an opposite direction.  While C. glomerata learned to prefer the odour of plants with intact roots, C. rubecula learned to prefer the odour of root-infested plants. These findings stress the importance of not only assessing the influence of root herbivores on the responses of inexperienced parasitic wasps, but of also taking learned responses into account. In a publication that will soon appear in Oikos the authors discuss the possible reasons why these two parasitic wasp species respond so differently towards the presence of root feeders.

What are the chances that the reefs recover? And how likely is it that they just turn into seeweed-dominated ecosystems instead?  Important issues that Peter Mumby and his colleagues have studied and modelled in the new Early View paper “Evidence for and against the existence of alternate attractors on coral reefs”.

Here’s Peter’s summary of the study:

Coral reefs have been heavily stressed by local anthropogenic disturbances, like fishing and pollution, as well as global events such as ENSO which can cause coral bleaching and wreak devastation on living coral. Ideally, corals would recover after some kind of disturbance but a number of studies have documented a lack of recovery and even continued decline of corals rather than return to a coral-rich ‘attractor’. This raises the question, ‘do coral reefs exhibit multiple attractors?’. If they do, then it is possible for negative feedbacks to emerge that not only prevent reef recovery but reinforce themselves and trap reefs within an undesirable state, often dominated by seaweed. If reefs do become trapped in an undesirable state it might prove extemely difficult for management to reverse the decline and facilitate the return of a healthy ecosystem. 

 

Ecological models of coral reefs have studied the effects of various disturbances including the fishing of herbivores such as parrotfishes. Theory predicts that Caribbean coral reefs do indeed exhibit alternate attractors particularly in their somewhat degraded states today. However, empirical studies have claimed to find no evidence to support this theory. There is, therefore, a controversy over whether reefs can become trapped in seaweed-dominated systems. In this paper we argue first that the empirical studies were incapable of testing for multiple attractors. We then provide new comparisons between theoretical predictions and field observations, both of which are consistent with multiple attractors. However, it is also possible to fit a simpler model to empirical data that does not exhibit multiple attractors. When we take a careful look at this model we find that it makes several troubling ecological assumptions, which lead us to doubt its veracity.

 

Proving the existence of multiple attractors is extremely challenging and there is, as yet, no definitive proof either way. However, the weight of theory and field observation appears to support the notion for Caribbean coral reefs. Given this, and it’s important conservation implications, we feel that management should proceed on the conservative – and more likely – assumption that reefs can become stuck in seaweed states if stringent steps are not taken to increase their resilience.

The Ecology of Playing Dead – when not needed to…something that Xinqiang Xi, John N. Griffin and Shucun Sun have diged deeper into in their new Early View paper “Grasshoppers amensalistically suppress caterpillar performance and enhance plant biomass in an alpine meadow”.

Read Shucun Sun’s story about Playing dead behaviour in grasshoppers:

As a child, I would often wake in the middle of the night thinking I could hear a burglar in the kitchen downstairs (in reality, my family cat coming through the cat flap). I would lay there, alert in bed, not daring to move in case I would be heard. By mistaking sounds of the cat for those of a burglar, I had inappropriately employed a danger avoidance strategy, costing myself much-needed sleep. We know that, in nature, prey are often highly-tuned to the signals of their predators and take action to avoid predation, like growing defensive body armor, shifting habitats, or even playing dead. Prey take these energetically demanding measures because being eaten tends to be rather more costly to one’s fitness! However, just like my childhood anecdote, prey species can get it wrong and misidentify a friend for a foe, reacting to cues from animals within their trophic level (competitors) that pose no predation threat. This sort of interaction could be common in nature and may not only incur a cost for the ‘victim’ but also have knock-on effects to other species that interact with them.

In our paper, we describe and explore the direct and indirect consequences of interactions between two common grazing insects in alpine meadows of the Tibetan Plateau in northwestern China. We ran a season-long field experiment in which we manipulated the presence and absence of the caterpillar, Gynaephora alpherakii, and grasshopper, Chorthippus fallax, in enclosures, and measured responses of both grazer species and their plant resources. After two months we discovered a strong negative one-way interaction between these species – the seldom considered form of interaction known as amensalism. While caterpillars showed reduced growth, survival, egg production, and delayed metamorphosis in the presence of grasshoppers, there was no reciprocal negative affect of caterpillars on grasshoppers. Because caterpillars are voracious grazers, changes in their activity and survival caused by the presence and absence of grasshoppers propagated to influence the composition and biomass of plants.

We put the amensalistic interaction down to a case of mistaken identity. We observed that by whacking into – and landing heavily upon – grass stems as they move about the meadows, grasshoppers trigger a death-feigning response in caterpillars whereby caterpillars, upon perceiving risk, drop to the ground from the grass stems and leaves where they forage, cease movement, and curl up for about 20 minutes before resuming foraging. Repeated disturbances from the seasonally abundant grasshoppers could have significant effects on feeding time and energy uptake. Indeed, caterpillars in the same enclosures as grasshoppers were observed actively foraging significantly less frequently than when they were alone – evidence of the cost of mistakenly playing dead and helping to explain grasshopper effects on caterpillar growth, timing of metamorphosis, and grazing impact on plants.

Our study provides a rare example of amensalism in a natural ecosystem and shows that it can result from a previously unappreciated mechanism – mistaken identity. Furthermore, this work highlights that such interactions can have significant consequences for the functioning of ecosystems, as revealed by marked shifts in the relative abundances of plant functional groups and overall biomass. Strong amensalistic interactions, if common, could have consequences for our understanding of key issues, such as the evolution of risk-reducing behaviors and traits and the link between consumer biodiversity and ecosystem functioning.

In the new Early View paper “Predator-mediated interactions between preferred, alternative and incidental prey in the arctic tundra”, Laura McKinnon and her colleagues used the Arctic Tundra in Canada as a natural laboratory to study predator-prey interactions.

Here is Laura’s short version of the paper:

Predators can have direct impacts on prey populations by decreasing survival and fecundity, and in turn, prey populations can also drive predator densities.  These interactions between predator and prey can often lead to coupled cycles in population abundance, many studies of which have become classic textbook examples in ecology.  More recently, these models have been expanded to incorporate multiple prey species and even multiple trophic levels in order to have a better understanding of the causes and consequences of predator prey interactions in more complex realistic environments.  However, testing these models in complex ecosystems can become rather cumbersome due the sheer number of interactions between species.  Luckily, there are some terrestrial ecosystems, such as the Arctic tundra which provide less complex natural laboratories in which to study trophic interactions between predators and multiple prey items.   In our recent study, we took advantage of this natural laboratory to study indirect interactions between preferred, alternative and incidental prey.

In the arctic tundra, numerical and functional responses of predators to preferred prey (lemmings) affect the predation pressure on alternative prey (goose eggs) and predators aggregate in areas of high alternative prey density.  Therefore, we hypothesized that predation risk on incidental prey (shorebird eggs) would increase in patches of high goose nest density when lemmings were scarce.  By measuring predation risk on artificial shorebird nests in quadrats varying in goose nest density on Bylot Island (Nunavut, Canada) across 3 summers with variable lemming abundance, and monitoring quadrats for predator activity, we provide evidence that the abundance of preferred prey influences the indirect relationship between alternative and incidental prey.  Predation risk on artificial shorebird nests increased in the presence of increasing goose nest densities, especially at low lemming abundance, as predicted.  In addition to supporting our incidental prey hypothesis which suggests that when preferred prey decrease in abundance, short-term apparent competition via aggregative response can occur between alternative and incidental prey, these results also provoke interesting applied questions regarding the potential effects of increasing goose densities on incidental prey such as shorebirds.

Seed diseprsal by animals is an important ecological service. How selective or general the animals are in their choice of fruits to eat might have a huge effect on dispersal of the plants. Read more in the new Early View paper “Individual variation in resource use by opossums leading to nested fruit consumption” by Mauricio Cantor et al.

Here is the authors’ own summary of the paper:

Seed dispersal by fruit-eating vertebrates is an important ecological service that has consequences for the plant community and regeneration process. Despite recent findings on the ecological relevance of within population diet variation far less attention has been devoted to the role diet variation for ecological services, such as seed dispersal. In this paper we unravel fruit consumption patterns by the white-eared opossum (Didelphis albiventris), a South American didelphid, which is regarded as an important seed disperser commonly found in disturbed environments, where vegetal regeneration is especially required.

We detected fruit consumption patterns suggesting these opossums may differ in their degree of fruit selectivity what may result in heterogeneity in seed dispersal efficiency within the population. In this sense, the actual result of the seed dispersal provided by these animals probably differs from what one would expect from the average behavior of the population. The result of such heterogeneity would probably be dependent on the proportion of opportunistic and selective individuals in the population. This frequency-dependent seed dispersal may have implications to both plant individuals and species, affecting plant performance and the local plant community composition.

Oikos is changing it’s cover style in 2013. Replacing the quote, there will now be a photo. We therefore, as an annual competition, call for photos illustrating the Oikos’ goal of Synthesising Ecology. We seek a photo also demonstrating ecology in action (e.g. processes or interactions), not only a single organism or a landscape.

Please send your photos together with the oikos-photo-competition-form2 to oikos@oikosoffice.lu.se, with Photo competetion as subject, before January 31st 2013. The winner will be awarded a book price from Amazon for a value of 100 Euro. The winning photo will be at the cover of all issues of Oikos from April 2013-December 2013. A selection of contributions will be exhibited at the Oikos meeting in Linköping, Sweden Feb 4-6.

Competition Rules:

Entries must be digital images, submitted electronically, in jpg or tiff-format. Images must be available in 300 ppi.

Digital enhancements must be kept to a minimum and must be declared. Both the original and the enhanced image must be submitted.

File names must include appplicant’s surname.

Photos must be accompanied by an entry form that describes illustrated species and scene. Download the oikos-photo-competition-form2

A prize committee consisting of Managing Editor, Editor in Chief, deputy editors, Technical Editor of Oikos and the Director of the Oikos Editorial Office, will judge which photo that best suits our requests. The decision by the committee is final.

All submissions will be entered under a Creative Commons License and will be displayed on Oikos webpage and social media and may be used  for commercial purposes. Download Creative Commons License here.

Oikos takes no responsibility for submitted images being lost, damaged or dealyed.

Invasive species may actually increase resistance to climate changes. Celia Olabarria and co-workers studies this interaction in marine macroalgal assemblages.  Now on early View: Response of macroalgal assemblages from rockpools to climate change: effects of persistent increase in temperature and CO₂

Here is a short summary by the authors:

Climate change is one of the greatest threat  that marine systems are facing. Changes in ocean temperature, biogeochemistry, sea level, UV radiation, and circulation patterns have been identified over the last few decades. Specifically, warmer and more acidic oceanic water (due to the increase of CO₂ in the atmosphere and oceans) are of great concern to marine biologists. Non-indigenous species are also impacting marine communities around the world at an unprecedented rate. These species are often ecosystem engineers (e.g. brown canopy algae) that can replace native species and their functional role in the ecosystem, or modify habitat characteristics and food sources for consumers. We do not have information about how invaded communities will respond to climate change compared to non-invaded communities.

Marine macroalgae that dominate the rocky intertidal in most oceans, and in temperate and Polar regions cover rock surfaces in the shallow subtidal, make a substantial contribution to marine primary production (10%) and describe important ecological functions. They may be also actively involved in lowering global warming and climate change. Research about effects of different climate change scenarios on macroalgae has found quite variable and species-specific responses. Until now, most research has focused on the effects of climate change on single macroalgae species, rather than on whole communities. While this approach is useful for understanding species-specific mechanisms behind the effects of environmental changes, it ignores species interactions which may buffer or amplify individual responses thereby altering predicted assemblage-level responses.

Macroalgal assemblages from rock pools are interesting model systems to study climate-driven changes because they are composed of different morpho-functional groups of varying diversity and identity of species. Despite coping with daily and seasonal variations in pH and temperature, their response to more persistent changes are unknown. We were able to manipulate temperature and CO₂ concentration in mesocosms to evaluate how these to climate-change factors affected several ecosystem functioning variables at both individual and assemblage level. For that, we used synthetic macroalgal assemblages of varying diversity and identity of species resembling those characteristic of rock pools.

Results revealed that the increase in temperature and CO₂ concentration may interact and affect the functioning of coastal macroalgal assemblages, with effects largely dependent on species composition of assemblages. Although the effects of assemblage richness were mostly negligible, significant differences were found between the response of native and invaded assemblages. Data suggested that  invaded assemblages might be more resistant in the predicted future scenario of climate change. This paper emphasises the importance of using multiple stressors-study approaches at community level to get better predictions of climate change impacts on ecosystem functioning.

Photo: F. Arenas and M. Matias

Protein or fat in food – which is best? Well, if you’re a female preying mantid, you should definitely go for the high-protein diet! Females on high-lipid diet attract much fewer males than females on high-protein diet. These results are presented in the new Early View paper “Macronutrient intake affects reproduction of a predatory insect” by Katherine L. Barry and Shawn M. Wilder.

Here is a short summary by Katherine:

We tested how diet affected the reproductive success of female praying mantids by feeding them live locusts that were injected with solutions of lipid or protein.  Not too surprisingly, females fed high-lipid locusts gained more fat and produced about half as many eggs as females fed high-protein locusts. 

We also tested female attractiveness by placing females in small mesh cages (that excluded visual cues) within large enclosures, and allowing males to choose between females from the different feeding treatments.  Usually females with more eggs are more attractive than females with less eggs and, in our study, the high-protein females attracted more males (56 males) than the high-lipid females (1 male).  However, the effect was much more extreme than we predicted.  In previous studies, females were fed a standard diet of crickets, and individuals with as few as one egg were able to attract up to three males.  But in our study, females on the high-lipid diet had over 20 eggs on average but only one female attracted one male.  Hence, diet quality seems to have a large effect on the quantity or quality of pheromone produced by females.  It would be interesting to test how diet mediates pheromone production in praying mantids and if similar effects occur in other species of arthropods.

Do you have any “helper” around you? Maybe are you one yourself? “Helpers” are those researchers who regularly provide valuable feedback to their colleagues’ manuscripts and to scientific discussions.  Who regard this feedback as part of the research, and a part of their working tasks. However, their input is awarded as best with their names in the acknowledgement of the publication, and not that often in the author field.

Alexander Oettl, a professor in Immunology at Georgia Institute of Technology, Atlanta, USA, studied the effect of “helpers” by comparing their colleagues’ impact of papers (IF of journals, n publications and citations) before and after the “helpers” involvement.  What he found was a clear positive effect of the involvement of the “helpers” for their colleague’s publications.

The question is – how are these helpers awarded? In evaluations of applications for academic positions and research grants, factors as large numbers of highly cited papers get higher rates than increasing over all scientific quality in the group or at the department. Perhaps it’s time for a new metric to take into account – average acknowledgements per year?

Read Oettl’s paper in Nature here  (Figures from Oettl’s paper)

You can now find a list of the most cited Oikos papers 2011, that were published in 2009 and 2010, on our webpage.

On top of the list,  is “A consumer’s guide to nestedness analysis” by Werner Ulrich, Mário Almeida-Neto and Nicholas J. Gotelli.

Here is a short description by Werner Ulrich, on what it’s all about:

Ecologists look for patterns in nature. The nested pattern – in which the composition of small assemblages is a nested subset of larger ones – is one that received a lot of attention, both because it is so simple and because it is so common. In biogeography, if sites are ordered by area or along an environmental gradient, a nested pattern can be interpreted as an orderly loss of species along the gradient. This is the most common interpretation of nestedness. It was popularized in the 1980s by Bruce Patterson and the late Wirt Atmar, who introduced a nestedness temperature calculator, compiled a large set of ecological presence-absence matrices from the published literature, and detected nestedness in most of them. Since then, much research has been devoted to articulating alternative mechanisms for nestedness, and developing appropriate metrics and null models for testing the pattern. Nestedness has also been used in food web or species interaction analysis, population genetics, and even molecular biology. However, the nestedness tale is also a story of failure and a warning on the challenges of statistical pattern analysis in ecology. Many studies have unfortunately used ad hoc measures of the degree of nestedness, inappropriate statistical benchmarks, and questionable ecological arguments. That was the point where we (Nick, Mario, and I) stepped in. The origin of our “consumer’s guide” paper was from an idea of Mario’s, who noticed that the quantification of a nested pattern went into a wrong direction. He asked me to take part in the development of a new metric, and the resulting Oikos paper was a success. We then tried to give guidelines for proper pattern identification and testing. During the writing, we noticed how many snags even a simple pattern like the nested one provides for researchers. Apparently, many other scientists shared our views. Our impression is that the quality of nestedness research has improved during the last few years, and we hope that our review has contributed to that trend.

During the work on nestedness, we started developing new metrics to quantify observed patterns and expanded the framework for proper statistical testing. Two new Oikos papers by Nick and me on statistical challenges and on pattern detection in ecology are the fruits of these efforts. We can only hope they will become as popular as the “consumer’s guide” to nestedness.’

Do you remember the Correspondence in Nature about contributions by women to Nature News and Views, that I wrote about here earlier this autmun? Obviously, the paper made the editor’s of Nature to analyze their situation and to come up with a solution to the problem. The recipe is to ask all editors to make an extra “concious loop” to identify five women to ask when commissioning articles and similar tasks. Most interesting though, is the statement that ” But it is certanly the case that women typically spend more time than men as housemakers and looking after children, further reducing the time available for journal contributions”. I wonder – how many times have Nature editors got that reply from an invited woman? -Sorry I don’t have time to write an invited paper to Nature, have to look after the kids you know? I’m pretty sure that there is no single female scientist out there who makes a choice between householding and writing Nature papers.

Here is Nature’s reply

But I’m curious – are the authors of the original paper happy with the response they have got? From Nature and from others? I asked one of them, Johanna Stadmark some questions:

1. How much have you and Daniel been involved in the response article? Got the chance to read it before publication?

Nothing, we did not know it was coming, and were happily surprised last Thursday.

2. How easy was it to get Nature publish a paper critisizing their work?

They immediately showed an interest in our study, but with revisions and comments back and forth it took some time. A correspondence should view our opinion, so we did not want to accept all suggested revisions. Nature edited our piece, but we had the possibility to make changes. I think it is of utmost importance for the journals to also accept criticism on their work, it shows that they are serious in their work.

3. What do you think of their reply? And about their suggestion to solve the problem?

I am happy that the idea to think outside of your own network was one thing that they suggested. If you reflect on how you are doing things you also have the possibility to make changes where necessary.

4. Do you think things will change now?

I do. The aim of our piece was to point at an unconscious bias that is occurring, not only in the leading science journals, but also at conferences, workshops etc. Over the last days we have received emails from people telling us where the Nature Editorial has been distributed and if some of these people change the way of selecting people for different tasks we have succeeded.

5. What advice can you give Oikos’ editors to avoid gender biases? (We have just started to invite authors to write forum papers, for example).

Have a protocol, to avoid using the “standard network”. Go and find the best authors irrespective of gender or ethnicity or other irrelevant conditions!

6. And finally, How big do you think, the problem of women spending more time than men householding and caring for children, is for invited papers in Nature?

I do not think that is important. Approximately half of the invited authors are full professors and if you have come that far in your career you have been able to deal with the so-called double tasks. And if you are invited to write a piece like a News & Views- or Perspectives article you do not want to miss the opportunity and you would give it a high priority.

I think the householding and caring for children in some cases can play a role in the advancement of the career and what kind of work you choose (teaching, research, administration). However, there are countries where public day care has been available since the 70’s and where caring of children should not be a task designated to women only. (I know it takes a long time to change society, and we are still not there, but to use “caring for children” as an explanatory parameter is not a good way to go in the discussions of the future, since it could be a fulfilling of an unwanted condition.

H-index, Impact Factor, citations, number of publications per year – metrics all around the scientist. The currency of science. Has it gone that far that the metrics is about to kill scientific quality?

This “quantity mantra” – the obsession with measuring scientific quantity – and not quality- was recently criticized by Joern Fischer, Euan G. Ritchie and Jan Hanspach in TREE. They argue that metrics has lead to an increased number of publications, larger research consortia and more administration. More papers published means more time spent on reading papers, reviewing papers and editing papers. With a general limit of 24 hours per day, that inevitably means less time for other activities. And it’s particularly reflection time and time spent to stimulate creativity that is suffering most, according to Fischer et al. This in turn, leads to decreased quality of science. Is this the way we want to go? The paper finishes with “Starting with our own university departments (but not stopping there), it is time to take stock of what we are doing. We must recreate spaces for reflection, personal relationships, and depth. More does not equal better.”  The question is, How?

Good place for reflection…

As a reply to Fisher et al.’s paper, Panu Halme, Atte Komonen and Otso Huitu transfer the problem from individual researchers and departments to science politics and funding strategies. They argue, that the main problem lies in the absence of scientific thinking among senior scientists. “Senior scientists rarely enjoy the luxury of having time to read about and contemplate the theory of their field, let alone participate in the gathering of primary data in the field or laboratory. Halme et al.’s solution to this problem, and suggested mean to leave room for slower science and increased quality, is to limit the numbers of students associated with each professor, and funding forms enabling seniors to focus exclusively on science.

In a reply, Fischer et al. actually comes up with a number of hands-on solutions, both for individual scientists, department leaders, science politicians and decision makers and for funding agencies.

Is it the increased quantity of publication that actually causes the increased stress for scientists? And how should the problem best be solved? Bottom up or top down? How do you release time to think deep, scientific thoughts and to reflect over your research?

Fischer et al.’s “Academia’s obsession with quantity

Halme’ et al.’s Solutions to replace quantity with quality in science

Fischer et al.’s “An academia beyond quantity…”

Let me introduce you to our new Subject Editor, Dr. Matty P. Berg, Vrije Universiteit Amsterdam, the Netherlands.

– What gets me out of bed every morning is the question what determines the diversity and composition of soil fauna communities, Matty says.

 What’s you main research focus at the moment?

My research focuses on the role of trait diversity in community and ecosystem ecology and can be divided in two major research areas.The first focal point is on the role of traits, both inter- and intra-specific, for the regulation of community structure. I measure functional traits of soil fauna, especially terrestrial isopods and springtails and use field experiments and trait analysis to study temporal and spatial changes in soil invertebrate community composition, at a hierarchy of spatial scales. The second focal point is on the role of traits in ecosystem ecology.This focal point comprises work on the role of trait diversity, both on a  species and community level, for the regulation of ecosystem processes. I measure traits and conduct experiments to understand how environmental variation influences ecosystem processes, trough alteration of species composition and interactions, using a response-to-effect trait framework. More recently I start to get interested in the importance of trait variability and plasticity in these research areas.

Can you describe you research career? Where, what, when?

I have studied Biology at the University of Amsterdam, with a major in Ecology, Biogeography and Taxonomy (1988-1992). During my internship I have studied the effect of changes in springtail abundance on the fat storage in carabid beetles and their reproductive output in coniferous forests. I did my PhD at the VU University, Amsterdam on the effects of enhanced atmospheric nitrogen deposition on soil food web structure and how changes in food web composition affect C and N dynamics in soils (1992-97). After that I did a Post-Doc at the Swedish University of Agricultural Sciences (Uppsala, Sweden) where I studied how competition between two functional groups of Basidiomycete fungi effected wood decomposition (1997-98). About 1.5 years later I returned to the VU university were I was appointed for five years as a Royal Dutch Science Academy-fellow. During this period I studied the effects of species richness and composition on the resilience of springtail communities to extreme events and the role of species composition of macro-detritivores for litter decomposition  (1999-2004). Since then I have an appointment as an Assistant professor (till 2011) and currently as an Associated professor in Soil Community Ecology. My main focus is currently on spatial ecology and on functional diversity.

How come that you became a scientist in ecology?

I am a true field ecologist. Already when I was young my main interest were found outdoors. My grandfather took me out to the Dutch polders on Wednesdays and introduced me to hares, wetlands birds and aquatic life. I guess like most scientists I started with birds and plants and was wondering why species occur where they do. The reason why I took up Biology was that I wanted to know how the natural world around me works. How are natural communities maintained? How do all these species interact? What is determining their composition? This question still lays behind most of the projects I am currently working on or are involved in. I have a second interest in the taxonomy and systematics of soil fauna, but during my BsC it became clear that career wise this was not the avenue to take. This is something I keep for my spare time.

What do you do when you’re not working?

To be honest the line between work and hobby is very thin. Natural history is my passion and in my spare time I can be found outdoors looking down for soil animals (or up for birds). I am a member of the European Invertebrate Survey, a society that aims to increase the knowledge on the distribution, ecology and protection of invertebrates. The society is based at the Naturalis Biodiversity Centre, Leiden where I am an associated researcher. As co-ordinator of the isopods, centipedes, millipedes, and collembolans survey groups  I make regular field surveys all over the country, study museum collections, describe new species for the Dutch fauna, make identification keys and try to make others interested in the wonderful world of soil critters. But I can also appreciate good music, nice food, and I am a sucker for a good glass of single malt whiskey to be consumed  in company of friends or colleagues.

So those small small seeds produced by plants have actually big effects on plant demography. Read more in the Early View paper “Non-native conditions favor non-native populations of invasive plant: demographic consequences of seed size variation?” by José L. Hierro et al. 

Or be quicly updated by Josés own short summary:

We conducted a reciprocal common garden in part of the native (southwestern Turkey) and introduced (central Argentina) range of a globally distributed plant invader, Centaurea solstitialis (yellow starthistle, Asteraceae) to explore the idea that the demographic success of the species in Argentina relates to differences between native and introduced populations.   Unusual among common gardens, our experimental design included seed additions to explicitly evaluate population level responses.  We found that seed mass was two times larger for Argentinean than Turkish populations.  Similarly, plant establishment at the end of the experiment was greater for Argentinean than Turkish populations, but only in the common garden in Argentina.  In Turkey, we detected no differences in plant establishment between population origins.  Our results suggest that increased seed size in Argentinean populations may have demographic consequences under central Argentina conditions that can contribute to the invasive success of C. solstitialis.  Our study offers the most complete evaluation to date to the idea that variation in seed size can contribute to differences in plant density between native and non-native distributions of invasive plant species.

Field site in Turkey (native)

Field site in Argentina (introduced)

 

When I did an undergraduate project at Silwood Park, my supervisor, Hefin Jones used to say that ecological research is about 10 % inspiration and 90% transpiration. And this is exactly what Winfried Voigt report about in his story about his and his colleagues Early View paper “Bottom–up and top–down forces structuring consumer communities in an experimental grassland” (Rzanny et al.). He story also shows what might be the outcome of large collaborative projects.

Gathering up sufficient and useful data for answering questions concerning entire communities is always a strenuous and costly job. It is actually only feasible when working in cooperation with a large team. We were lucky to be involved in an appropriately large team, the Jena Experiment, a controlled biodiversity experiment [http://www.ecology.uni-jena.de/en/Jena_Experiment_Inst_of_Ecology.html]. The dimensions (10 ha, 80 plots each 20×20 m with a set plant species diversity of 1, 2, 4, 8, 16 and 60 as well as 1,2,3 or 4 functional plant groups, and numerous smaller plots) are unique and  turned out to be the right platform for asking “bigger” questions about structure and function in grassland communities. A lot of periodic work, in particular weeding, was done by a capable maintenance staff (5 professional gardeners and numerous student assistants) so that the only thing left to do was to collect our own data. Nevertheless, for our closer small team (with some support  of a few student assistants) even that was quite a strenuous job but all the effort and suffering (not to say blood, sweat and tears) are not  always obvious if one looks at the end result on just a few hundred Kbyte of data we hold in an excel file. We collected arthropods 5 times, from May to October in 2005, on 5 quadrats randomly placed within the core area of 50 big plots (16 monocultures, 16 four-species, 14 sixteen-species and four 60-species mixtures) using suction samplers combined with biocenometers (see photograph) as well as using pitfall traps. All in all, we successfuly accrued 322 arthropod species/taxa with 81658 individuals that we could exploit in the end.

Identifying the key factors for structuring ecological communities is at the heart of ecological research. Most studies dealing with this question on community level rely on lumped, aggregated variables such as summed species abundance, biomass or diversity measures or they confine to a small part of species usually one or a few taxa.

We already developed a different approach 10 years ago by assigning all species to functional groups representing approximately the entire community. Because we hold all functional groups as matrices containing abundances of their members (species), we acquire a sufficient simplification, while retaining full species information. As we see ecological communities as a system of interdependent functional groups, we performed an exploratory multivariate analysis, explicitly addressing species composition of functional groups. We used species resolved plant biomass and arthropod abundance data from the Jena Experiment to estimate the dependencies among plant – and consumer functional groups, thereby accounting for spatial effects and differences in soil conditions.

Using a set of five groups of biotic and abiotic predictor variables (Plants, Herbivores/Detritivores, Carnivores, Soil, and Spatial patterns), we aimed to determine the independent and shared fractions of variation explained by these variables in the composition of all consumer functional groups. Depending on the trophic level of the predictor variables, we quantified the relative roles of top-down and bottom-up effects.

It turned out that legume composition explaines the highest fraction of variation in virtually all consumer functional groups, indicating that legumes play a key role in controlling multiple ecosystem processes. Both plant species richness and plant functional richness show significant effects on (nearly) all functional groups, however, the fraction of variation explained is always exceeded by the fraction explained by plant community biomass. Carnivore composition explain significant fractions of variation in many functional groups, the same applies for the soil and space variables. Consequently, we conclude that bottom-up effects seem to play the most important role in structuring the consumer communities in our experimental system, but at the same time top-down effects are still important for the majority of arthropod functional groups.

Sometimes it’s worth bringing good old science back into the light. Hideyuki Doi and Terutaka Mori were inspired by two papers from 1932 and 1953 about species abundance distirbution and brought them into modern days’ science. Read the paper “The discovery of species–abundance distribution in an ecological community” on Early View. Here’s the author’s own background story:

Species–abundance distribution (SAD), representing relative species abundance, is one of the most basic descriptions of an ecological community. The description can represent more detailed attributes of the community than species richness. Universal observations that few species in a community are dominant, but that many more species are rare, can be neatly encapsulated in a SAD, but not represented by species richness.

Prof. Isao Motomura (1904–1981, photo) first found a SAD pattern for some animal communities and then published a notable paper in 1932. Motomura (1932) described SAD in the following way: ‘In a community, there are generally many more species with relatively low abundances. When the species found within a quadrat are ranked according to abundance (i.e. the order of dominance in the community), a definite graphic pattern is observed between the rank and abundance of species’. He found that a straight line is produced when logarithm of abundance is plotted against rank, and then fitted observed SAD to “geometric series”. Motomura’s study is the first discovery of a SAD pattern, but has often been overlooked or incorrectly cited, probably due to being published in Japanese.

In this article, we in-deep introduce the works of Motomura and the subsequent research history of SAD. Specifically, we also introduce the work of Numata et al., another Japanese paper, which provided the biological explanation for Motomura’s model of SAD. Numata et al. (1953) showed that Motomura’s model (i.e. geometric series) is explained by supposing that species occupy the available area according to the rank of a set of ability for individual and species survival (i.e. reproduction, competition, etc.). Therefore, they provided biological explanations with a deductive approach for Motomura’s model in which an inductive statistical approach was employed. We believe that the field of SAD is increasing in importance and activity, because SAD has proven to be one of the most important fundamental tools in community ecology and management. Motomura (1932) paper also includes an important suggestion for ecologists: ‘In a natural ecosystem, it is very unusual to find such geometric series for the abundances of species coexisting in a habitat’. The finding of such a surprising pattern in ecological communities therefore represents a frontier of ecological research. Our motivation for finding a new general rule in ecology is highly recommended.

Root competition appears to effect sex allocation in plants. Åsa Lankinen and her colleagues have studied this in the Early View paper “Allocation to pollen competitive ability versus seed production in Viola tricolor as an effect of plant size, soil nutrients and presence of a root competitor”. Here is a short summary by Åsa:

Even though plants lack brains, there is clear evidence that they can perceive and respond to their neighbours. For example, in some species plants can sense airborne chemicals transmitted from the leaves of another plant attacked by herbivorous insects, acting as a cue to start the induced defence system. Another example of plant communication is the possibility to detect the presence of self vs. non-self roots in the soil. Presence of unrelated root neighbours can even cause plants to allocate relatively more resources to their roots than to their shoots, thereby allowing more effective root-uptake when competitors are present. But can plants also use these kinds of cues to optimize their mating success, such as altering relative allocation to male versus female function in hermaphroditic plants depending on the presence or absence of competitors? In hermaphrodite animals, the social context (e.g. group size) can clearly influence male-female allocation.

In this study on violets, a hermaphrodite annual, our results indicate that sex allocation may not only be size dependent and influenced by soil nutrients, but also affected by presence of a root competitor. Taking the additional aspect of social environment into account also in studies on sex allocation in plants has the potential to increase our understanding of sex allocation across taxa.  This knowledge might help us answer difficult questions such as how evolutionary transitions can occur between breeding systems.

In the new early view paper “Do physical plant litter traits explain non-additivity in litter mixtures? A test of the improved microenvironmental conditions theory”, Marika Makkonen and co-workers, present a new theory on decomposition rates. Here’s their own summary of the paper:

Terrestrial plant litter decomposition is a key component in carbon flux models. The models and thus the predictions they produce could be improved by ensuring the comprehensiveness of the variables included in the model and the close resemblances between nature and the input data. Usually the input data is derived from litter monoculture studies and this creates a crucial source of error, as monocultures do not present well the majority of land cover. Importantly decomposition rates usually differ between litter monocultures and mixtures. The causes for this non-additive effect are still debated and unclear. One plausible theory suggests that the non-additivity of litter mixtures derives partly from improved microclimatic conditions given by physically more diverse plant species in mixtures compared to monocultures. The physical characteristics of litter determine e.g. water acquisition and retention and thus alter the microenvironmental conditions determining the habitat and resource availability for decomposers.

We tested this theory in a dry subarctic birch forest in the Swedish Lapland in two contrasting moisture conditions. By testing some water holding capacity (WHC) traits, we found clear support for this theory and thus our results strongly encourage the inclusion of plant litter physical traits as the predictors of the decomposition rates. Yet the modeling will face more challenges as we found the direction of non-additivity (positive or negative deviation compared to monocultures) in litter mixtures to vary between climatic (moisture) conditions. Namely we found that the higher dissimilarity in WHC traits between the component litter species in a mixture increased synergistic effects in litter mixtures under limiting moisture conditions whereas, increased antagonistic effects were observed under improved moisture conditions. We also observed differences in non-additivity, its relation to WHC traits and their modifications by different climatic conditions between litter mixtures of varying decomposability further obscuring the process. Although the non-additivity of litter mixture remains complex, some major advances were made by this study.

A couple of weeks ago, I wrote here about the close connection between failure and success. And associated it with improvement of a manuscript due to a reject. Now, I also found some scientific support for this. Vincent Calgno and his co-workers have tracked the history of more than 80 000 scientific papers, published between 2006 and 2008 within the bioscience area. They found that papers that had been rejected in one journal and submitted and accepted in another one, gathered significantly more citations than papers accepted on the first try. Even if they were published in the same journals. Despite that 75% of the papers were published in the jornal it was first submitted to, the proportion of papers that had been submitted elsewhere, was actually higher for high impact journals such as Nature and Science, than it was for low-imapct, specialized ones.

So no more tears over rejects! Things will only be better!

So how good will not this one be?:

http://researchinprogress.tumblr.com/post/33698577212/reject-resubmit

At least here in southern Sweden, the autumn colours have been fantastic this year! As an evolutionary ecologist one starts wonder: why does trees differ in level of coloration? Is it only a benefit to the tree? Or are there costs associated with it as well? And why are some leaves red early in spring? In the new Early View paper, “Red young leaves have less mechanical defence than green young leaves”, Ying-Zhuo Chen and Shuang-Quan Huang have found answers to some of these questions. Here is a short version by Shuang-Quan Huang:

People in North Temperate Zone often enjoy seeing colorful leaves in autumn, an obvious phenomenon in deciduous forests. Evolutionary biologists Hamilton and Brown (2001) considered that autumn leaf coloration is expensive because it involves the costs of pigment synthesis, resource loss and loss of primary production (photosynthesis). A functional hypothesis proposed by Hamilton & Brown (2001) and Archetti (2000) suggest that leaf redness could be an adaptive strategy as a warning signal reducing insect attack (anti-herbivory hypothesis), but is still largely controversial.

Many species have red young leaves in spring. For example, an investigation of tropical plants in a Nature Reserve, Singapore showed that 60% species with young leaves were red (see Dominy et al. 2002). The anti-herbivory hypothesis has also been adopted to explain color change during leaf development. We are interested in why so many species produce constant green leaves in its life cycle if leaf-color change involves an obvious benefit (less herbivory). A similar question was asked by David Lee (2002) who argued that if anthocyanins in leaves confer some physiological/selective advantage, how do the species lacking anthocyanins compensate?

To test whether green leaves reduce herbivory by physical defense as an alternative to the supposed warning signal of red leaves, we conducted comparative analyses of leaf color and protective tissues of 76 woody species around our campus Wuhan University, a subtropical area in central China. We found that the species with green young leaves showed a significantly higher incidence of enhanced cuticle, multiple epidermis, and trichomes compared to species with red young leaves. This analysis suggests that green leaves may compensate for the lack of anthocyanins by adopting enhanced physical defense. Our finding of relatively poor mechanical protection in red young leaves may provide new evidence for the adaptive explanation of leaf color change.

It’s really nice to be able to present yet another new Oikos Subject Editor:

Shawn Wilder, University of Sidney, Australia.

1. What’s you main research focus at the moment?

My main research focus now is examining the nutritional requirements of spiders and comparing these requirements to the distribution of nutrients in prey to better understand how diet regulation behavior by predators affects the structure and function of ecological communities.  Recent work has shown that the nutrient content of prey can have large effects on the growth and reproduction of predators and that some predators will tightly regulate their diet.  I’ve been using the geometric framework of nutrition to quantify the nutrient requirements of a spider (redback spider, Latrodectus hasselti) and have measured the nutrient content of over 500 species of arthropods.  Future experiments and modeling work will combine this information to predict which prey or combinations of prey may be preferred by predators and how these prey preferences may affect prey populations and community dynamics.

 2. Can you describe you research career? Where, what, when?

My career began by helping with fieldwork on charismatic megafauna.  During undergrad, I was a field assistant on large-scale studies that captured, radio-collared, and tracked black sea turtles in the Gulf of California and, the next summer, black bears in the Blue Ridge Mountains of North Carolina.  The fieldwork experiences were amazing and motivated me to go to graduate school to become an ecologist.

For my M.S. at Miami University, Ohio I move to a smaller and more manageable study species, white-footed mice, and examined how fragmentation of their forest habitat due to agriculture affected their population dynamics.  However, in the lab next door, friends of mine were studying the behavioral ecology of wolf spiders, including chemical communication, predator-prey interactions and mating behavior.  I soon became very interested in spiders and began my Ph.D. studying the ecology and evolution of sexual cannibalism.  I was interested in understanding why cannibalism was frequent in some species but rare in others.  Female hunger had an obvious and large role in predicting cannibalism but my work also suggested that nutrition may be important.

I then moved to Texas A&M University for a postdoc to study the role of food-for-protection mutualisms in facilitating the invasive success of red imported fire ants, Solenopsis invicta, in the Southern USA.  Due to differences in competitor communities, fire ants have greater access to mutualisms in their introduced range in the USA than their native range in Argentina.  As a consequence, fire ants in the USA consume more carbohydrates than fire ants in Argentina and these carbohydrates significantly increase fire ant colony growth even when insect prey are available ad libitum.

I continued with my interest in nutrition by moving to the University of Sydney to study the nutritional ecology of carnivores with Steve Simpson.  I’ve since been promoted to Lecturer and received an ARC Discovery Early Career Researcher Award.  Australia has an exciting diversity of insects and spiders and I’m looking forward to exploring and studying them further.

 3. How come that you became a scientist in ecology?

My interest in ecology and nature developed at a young age.  I grew up in the Northeastern USA and my family spent a lot of time camping, hiking, and fishing when I was young.  I also spent a lot of time flipping over rocks and searching in tide pools for insects, spiders, salamanders and crabs.  I would even occasionally feed the spiders that lived in the backyard.  Fortunately, my parents were very encouraging.

4. What do you do when you’re not working?

I enjoy camping, hiking, kayaking, and fishing.  Sydney has been a great place both for work and fun.  Although it’s a big city, it is surrounded by National Parks that are easily accessible and have a lot of beautiful trails through rainforests, mountains, and cliffs overlooking the ocean.

I also enjoy traveling both for research and fun.  Some of my recent highlights for research trips include traveling around northern Argentina studying ants and traveling to the Northern Territory of Australia to study araneophagic jumping spiders.  I’ve also recently traveled to Thailand and South Korea, both of which were a lot of fun.

Own website:  https://sites.google.com/site/shawnmwilder/

…is explained in Miroslav Kummel et al.’s new online paper “How the aphids got their spots: predation drives self-organization of aphid colonies in a patchy habitat”.

A short summary is given here by Miroslav:

Spatial self-organization is the ability of a system to develop a spatially heterogeneous distribution of population sizes across otherwise identical locations This self-organization can result in static areas of high and low population density across otherwise homogeneous underlying conditions. Alternatively it can result in traveling population waves, or in spatial deterministic chaos. Self-organization has emerged as a key concept in population ecology, because it can fundamentally alter the outcome and stability of interspecific interactions. It has been studied extensively theoretically, but there are very few empirical studies that establish the presence and causality of spatial self-organization in the field.

 In addition, the majority of current studies in spatial ecology (both empirical and theoretical) examine self-organization in laterally connected systems. These are systems where spatial effects are strongly determined by distance (e.g. the probability of colonization decreases with distance) and adjacency. However, space can be conceptualized in ways that are different. For example, space can be conceptualized as a network of connected patches, where the connections between patches are determined by other variables than pure distance. Human examples of such networks include a network of airports connected flights, natural examples include a collection of food patches connected by ant trails. The “network” conceptualization of space is very new to ecology and allows us to address previously intractable issues. Recent developments in network theory show that self-organization is possible in other network topologies such as random or scale-free networks.

In the field system that we study, foraging flights of coccinellid (ladybug) predators connect spatially discrete colonies of aphids into a network that has topology more complex than a laterally connected lattice. We show that predation by coccinellids induced self-organization in sessile aphid populations into small and large colony sizes on otherwise identical racemes of Yucca glauca that grew in close proximity to each other.

The self-organization was supported by a bi-modal frequency distribution of aphid colony sizes, and by the structure of density dependence that showed multiple attractors. The position of the attractors matched the position of the two modes in the bimodal distribution.

 We demonstrated that predation was the key driver of self-organization both empirically, and through a simple field-parameterized mathematical model. In the empirical study we showed that the multiple-attractor nature of density dependence disappeared when coccinellids were experimentally excluded from the system. The simple field-parameterized mathematical model showed that the multiple attractor structure was likely a consequence of the distribution of coccinellids among the aphid colonies: coccinellid number increased as a power (less than one) of aphid colony size. Thus the self-organization likely originated from spatial foraging decisions of the coccinellids.

The nature of self-organization in our system resembles that which was found in mathematical models of more complex networks. Thus our study provides the first link between these recent theoretical developments and field ecology.

In the new paper “Adaptive foraging allows the maintenance of biodiversity of pollination networks” Fernanda S. Valdovinos and her colleagues present a new population-dynamics model for plant-pollinator interactions:

 Here’s Fernanda’s summary of the model: One of the main novelties of our work is the new model of mutualistic networks that we proposed. Our model includes the trophic dimension of mutualistic interactions, by incorporating a separated equation for the dynamics of the resources that plant species offer to their animal visitants. In this way we could incorporate to the analysis of mutualistic networks the next biologically important process: 1) the production and animal consumption rates of plant rewards, 2) the competition and/or facilitation among plants via shared pollen/seed animal vectors, 3) the competition among animals for plant rewards, and 4) the animals’ allocation of foraging efforts. These processes were neglected by the traditionally used models on mutualistic networks, which simply represent mutualistic relationships as phenomenological positive effects among species. I think that these four processes may affect the interplay of network structure and dynamics that some studies have documented during the last years, like are the effects of nestedness, connectance and richness on the species persistence of those networks.

We are very happy to congratulate Dr. Sharon Strauss, University of California, to being the winner of the Per Brink award 2013. Sharon will be awarded the Per Brink prize at the Oikos meeting in Linköping, Sweden in February 2013.

Here is a presentation of Sharon:

My research focuses on how organisms are influenced both ecologically and evolutionarily by the complex communities in which they are embedded, and by the inextricable interrelationship between ecology and evolution. The ecology of organisms reflects their long-term evolutionary history, with all its contingencies. The extent to which related species share and diverge in ecologically important traits, and how this shared ancestry affects community assembly is a growing area within ecology.  In addition, ecological dynamics and community assembly are influenced by microevolutionary change.  Ecological communities and abiotic environments exert selection on organisms; evolution in response to such selection, under the constraints of long-term evolutionary history, often results in populations that differ in traits from the parental generation. These different trait values, in turn, can feed back to affect the ecology of a system.

We can often predict how systems will respond under simplified conditions or when one ecological force is clearly dominant. For example, application of pesticides has consistently resulted in the evolution of resistance in insect pests (more than 300 spp.). When interactions are variable in space or time,  interactive in their effects on fitness, and when the selective effects of different agents are somewhat comparable in strength– as they are in complex communities– then our ability to predict how or whether traits will evolve, and how populations and communities respond through time, becomes much more of a challenge. As counterexamples, the ecology of introduced species, and the selective effects of  human actions that overwhelm other agents of selection on natural populations both represent useful, more simplified, contexts in which to explore the implications of natural community complexity.

The Per Brinck Oikos Award recognizes extraordinary and important contributions to the science of ecology. Particular emphasis is given to scientific work aimed at synthesis that has lead to novel and original research in unexplorered or neglected fields, or to bridging gaps between ecological disciplines. Such achievements typically require theoretical innovation and development as well as imaginative observational or experimental work, all of which will be valid grounds for recognition.

The /Per Brinck Oikos Award/ is delivered in honor of the Swedish ecologist Professor Per Brinck who has played an instrumental role for
the development and recognition of the science of ecology in the Nordic countries, especially as serving as the Editor-in-Chief for Oikos for many years.

The award is delivered annually and the laureate receives a modest prize sum (currently €1500), a diploma and a Swedish artisan glassware.
The prize ceremony is hosted by the Swedish Oikos Society. The award is sponsored by the Per Brinck Foundation at the editorial office of the journal Oikos and Wiley/Blackwell Publishing.

We are very happy to welcome Dr. Jessica Abbott as new Subject Editor for Oikos. And of course, we want to know more about Jessica so:

Jessica, what is your research about?

At the moment my main research focus is on how sexual antagonism influences an organism’s genetic architecture.  Sexual antagonism is when the same trait has opposite fitness consequences in males and females.  Sexually antagonistic genes and traits are interesting because they may hold the key to one of the long-standing paradoxes in evolutionary biology: the maintenance of standing genetic variation.  When selection is strong and traits are heritable, it is expected that standing genetic variance for fitness should be rapidly depleted.  Yet this is not what we see when we look at natural populations.  Sexual antagonism may provide an answer since it means that the fitness of any given allele is context-dependent, preventing rapid depletion of genetic variance.  I’m currently working on testing the hypothesis that sexual antagonism on the sex chromosomes maintains standing genetic variation across the genome, using two model systems: the fruit fly Drosophila melanogaster and the hermaphroditic flatworm Macrostomum lignano.

Can you shortly describe your career?

I am originally from Canada, and started my undergraduate degree at the University of Guelph.  During my third undergraduate year I came to Lund University as part of an international exchange program.  I liked it so much that I wanted to stay longer, and ended up living there for 8 years while completing a Master’s and and a PhD on female-limited colour polymorphism in the damselfly Ischnura elegans, under the supervision of Erik Svensson.  One of the female morphs is a male mimic, which benefits from reduced male mating harassment. This led me to become interested in sexual conflict in general, and in constraints on the evolution of sexual dimorphism and intralocus sexual conflict and sexual antagonism in particular.  In 2007 I therefore moved back to Canada on a Swedish Research Council-funded postdoc with Adam Chippindale at Queen’s University in Kingston.  It was there that I started working on sexual antagonism in fruit flies, using an established set of populations that had experienced male-limited experimental evolution for many generations.  In November 2009 I moved back to Sweden to join Ted Morrow’s lab at Uppsala University.  While there I carried out an investigation of my own set of experimental evolution populations, this time lines that had experienced male-limited X-chromosome evolution.  In 2011 I started a collaboration with Klaus Reinhardt from the University of Tübingen, on genotype-by-environment effects on sperm traits.  I started working in Lund again in February 2012, after receiving a Junior Researcher Project Grant from the Swedish Research Council, which has enabled me to set up my own independent lab.

How do you feel about becoming a subject editor at Oikos?

I’m excited about becoming a subject editor at Oikos.  I’ve been very active so far as a reviewer, both for established journals and within the new initiative Peerage of Science, but I’ve never worked as an editor before.  I’m looking forward to seeing the peer review process from the other side.

What do you do when not working?

I have two young daughters, so when I’m not working I mostly spend time with my family.  I love to read, so that’s what I do when I can find time just for myself.  Even though I’m busy I usually manage to finish a book once every couple of weeks.
Even more curious on Jessica? Visit her websites:

Institutional website: http://www4.lu.se/experimental-evolution-ecology-behaviour/people/principal-investigators/jessica-abbott
Own website: http://jessicakabbott.com/

Alien, invasive species are an increasing threat to biodiversity. In their paper “Competitive outcomes between two exotic invaders are modified by direct and indirect effects of a native conifer”, Kerry Metlen and co-workers has studied what two invasive species – a grass and a herb – and how they are affected by a native pine. Here, Kerry gives a short background to their study:

This research was inspired by a very striking pattern observable at undisturbed sites in the intermountain grasslands of western Montana, USA; Centaurea stoebe is supremely dominant in open prairie but virtually absent under the canopies of large ponderosa pines growing in the grassland.  At disturbed sites, any component of the native vegetation has been removed, C. stoebe appears to then move in aggressively, suggesting that some complex interaction among species drives this very simple pattern. 

 Extensive field observations confirmed the pattern that had seemed so obvious, as at this site just east of Hamilton, Montana, USA.  Germination experiments and extensive litter manipulation – in the field and in the greenhouse gradually allowed us to tease apart these complex interactions.  This fantastic adventure, lead us to discover that direct effects between species were insufficient to explain patterns of invasion of C. stoebe and Bromus tectorum and that shifting interactions among species gave a more complete picture of this dynamic plant community.

Humour is an important creativity booster. And science can be oh so serious sometimes.

Check out this site when you need to laugh…

And don’t ever believe that we editors, at various stages, are lacking empathy or an understanding of the consequences of our decisions and messages:

This is the result, we know:

http://researchinprogress.tumblr.com/post/33946389387/we-regret-to-inform-you-that-your-paper-has-not-been

Or this:

http://researchinprogress.tumblr.com/post/33884075941/we-are-pleased-to-inform-you-that-your-paper-has-been

That predator-prey interactions can be temperature-dependent is something that Angela Laws and Anthony Joern shows in the new Early View paper in Oikos “Predator–prey interactions in a grassland food chain vary with temperature and food quality”

Read their background story here:

“Grasshoppers are important components of most grassland ecosystems.  These abundant herbivores can influence many ecosystem processes such as nutrient cycling and primary productivity.  But the effects of grasshoppers on ecosystem processes often depend on the outcome of their interactions with other species, including predators.  For example, spiders are common predators of grasshoppers that alter grasshopper behavior and can limit grasshopper population size. But the outcome of species interactions can be sensitive to changes in many biotic and abiotic environmental factors.

We were interested in learning how temperature can influence predator-prey interactions between grasshoppers and wolf spiders.  Ectothermic organisms like grasshoppers and spiders are likely to be especially impacted by shifting temperatures, because temperature affects many physiological processes including feeding, activity, and digestion.  But temperature may also alter species interactions with effects on food web functioning.  In our system, grasshoppers prefer warm temperatures and are active during the day while wolf spiders prefer cooler temperatures and are crepuscular.  Therefore, we predicted that shifting temperatures can alter predator effects on grasshoppers by expanding (through cooling) or contracting (through warming) the total amount of time each day that both grasshoppers and wolf spiders are active.

We conducted a three-year field experiment to test these predictions using common species of grasshopper (Orphulella speciosa) and wolf spider (Rabidosa rabida). We set up field cages and stocked them with grasshoppers only or grasshoppers and spiders.  To alter temperature, we surrounded some of the cages with temperature chambers constructed of steel frames covered with shade cloth (decreased temperatures) or with plastic sheeting (increased temperatures).  Other cages were left uncovered as a control.  The roofs of these temperature chambers were mounted on garage door tracks and could be opened and closed.  The roofs only covered the cages during the morning and were left open for most of the day.

We found that spiders had strongest effects on grasshopper survival in the cooled treatments, and weakest effects on grasshopper survival in the warmed treatments, as predicted.  In some years, this led to the appearance of a trophic cascade (an indirect effect of predators, where predator presence leads to an increase in plant biomass) in cooled treatments, but not warmed treatments.   Our results show that the outcome of predator-prey interactions between grasshoppers and wolf spiders, and their effects on plant production, can shift with temperature.  Our data also suggest that wolf spiders may be less effective at limiting the size of some grasshopper populations under warmer conditions.”

Is there really a connection between biodiversity and conservation and Internet? Oh, yes, read Michal Zmihorski and his colleagues new Early View paper in Oikos, “Ecological correlates of the popularity of birds and butterflies in Internet information resources”.

Below, Michal tells us what made him and his co-workers to do this analyses:

“The idea concerning wildlife in the Internet resulted from a simple observation. Namely, we noted that different species are popular in the Internet whereas others are relatively rare. For each query Google provides the number of web pages containing the searched word(s) (here the name of a bird or butterfly). Consequently, we searched for possible mechanisms explaining the differences. More specifically, we expected that the patterns of popularity and rarity in the web were not random and should be somehow linked to the phenotype of particular species. Therefore we selected some basic characteristics of species, such as body size or migratory behaviour, and checked their importance in explaining the popularity on the internet. We excluded species whose names had more than one meaning. Initially we worked on Polish names of Polish birds but, following editors’ advice, we extended this to English names of British butterflies.

           

Several characteristics related to ecology and morphology of species were associated with their popularity in society. This in turn may have some obvious consequences for selection of species for conservation actions (e.g. as flagship species). We suggest that conservationists may use some phenotypic features of species in a more systematic manner to select for flagship species. However, to be honest, this is not of primary interest to us. The most exciting aspects of the association between phenotype and popularity is related to possible feedback, i.e. profits that popularity brings to a given species. First of all, we showed that there is some filtering of “colonization” of the internet by birds and butterflies (some features make species more effective in this “colonization” process). Secondly, the assumption that popularity in society is profitable for species seems to be true and may be related to the fact that organisms which are commonly known and well recognized by peoples may benefit from e.g. artificial feeding, nest-boxes, nest protection from predation and devastation, conservation actions, effective fund raising and so on (it is not easy to find references confirming this assumption, fortunately, we do not have to provide any in text for an Oikos blog!). If this is so the following mechanism can be proposed: the phenotypic features that makes a species popular in the Internet may also affect its fitness (because species that are popular in society may benefit from their popularity). Of course, the proposed mechanism has several weak points and needs to be confirmed, but in our opinion may be a catalyst for further studies. What is important is that if the mechanism works this means that natural selection may partially go through the virtual world of the internet, and such an idea is something new.

            All your comments and suggestions (including proposals for cooperation) concerning the topic of our study are highly welcomed. You have full text access to this content“

 

How close to a relative should one settle? David Aguirre et al have shown that relatedness has an effect on colonization and settlement in some species, at least.

Here’s David’s summary of the paper that is now on Early View in Oikos:

“In organisms with sessile adults (e.g. many plants and marine invertebrates) variation in the density of colonisers is known to have a profound influence on the structure of populations and communities. Recent studies also indicate that the relatedness among interacting adults can be an important driver of differences in ecological performance among populations. Thus, it is surprising that few studies have examined the effects of relatedness on the non-adult life-history stages, and thereby the effects of relatedness on colonisation processes. In our study we bridged the gap between these two lines of ecological enquiry, and found that the effects of relatedness on colonisation differed in direction and magnitude in four sessile marine invertebrates.”

In the new Oikos paper (now on Early View), “Simulated responses of moose populations to browsing-induced changes in plant architecture and forage production”, John Pastor and Nathan R. de Jager present a model examining how tree crown architecture affects moose populations. Here, they give a background to the study:

“In the recently published paper, “Simulated responses of moose populations to browsing-induced changes in plant architecture and forage production”, we report the results from a model we developed nearly a decade ago as part of Nate’s Master’s thesis at the University of Minnesota-Duluth. The model examines the feedback effects of moose browsing-induced changes in plant architecture on moose population dynamics. We were able to construct the model because of a very well thought out and executed experiment in northern coastal Sweden (Persson et al. 2005 a, b). Inga-Lill Persson and her colleagues  annually removed plant tissue from study plots in proportion to different moose population densities and also added corresponding amounts of urine and fecal material. By measuring the architectural responses of different tree species to simulated moose densities (De Jager and Pastor 2008, 2010) we were able to ask a very simple question: Can the forage produced by trees that have been previously browsed in proportion to known moose densities support the same moose population densities over the long-term? Our main finding of the field study was that some properties of the crown architecture of deciduous trees, such as fractal dimension and twig density, responded quadratically to increased moose population density. At intermediate moose densities, these properties more than compensate for reductions in twig size, leading to small increases in forage production.

Our approach to constructing the model was extremely simple, assembling these equations for the architectural responses of plants to known moose population densities and the winter food requirements of moose, but ignoring other known factors that influence moose population dynamics (e.g. animal feeding rates, population demographics) and other known effects of moose on ecosystems (e.g. changes in soil fertility). The point was to see if these architectural responses in isolation could in principle determine moose population densities and dynamics. In fact, it was the simplicity of the model that kept us from submitting it as a manuscript for several years. John developed a renewed interest in the model after receiving positive comments from colleagues in Sweden following a presentation in  2010. Indeed, the editorial reviewers at Oikos liked the model and our paper because of its simplicity, not in spite of it.

It turns out that the architectural responses of plants that we measured can produce realistic moose population densities for northern Sweden  (an average of ~10-15 moose/1000 ha). But these population densities were only sustainable at the sites with the highest productivity and with species compositions heavily weighted toward deciduous trees, which can overcompensate for lost tissue due to moose browsing.  One of the new things we found was the quadratic responses of plant architecture to moose population density, especially those of birch, produced oscillations in moose populations on highly productive sites. The lessons we learned from this model were, first, that architectural responses of plant crowns to browsing may play a more important role in regulating moose population density than previously suspected and, second, that these architectural responses might cause complex population dynamics such as population cycles.”

Link to Persson et al. 2005 a

Link to Persson et al. 2005 b

Link to De Jager and Pastor 2008

Link to De Jager and Pastor 2010

Recently, the Noble prize laureates for 2012 were presented. But what is it that turns these researchers into Nobel prize winners? What are the key factors that makes the difference between a winner and the average researcher?

My interest for thistopic, stems from my concern that many university departments are not very good at providing the creative environment that I believe is required to house a coming Nobel prize winner. Constant stress, strong hierarchy, too heavy workload and a culture of criticism toward new ideas and suggestions rather than an open mind, are factors actively inhibiting creativity. But providing a creative environment is important for any department  and any research group that strives, maybe not for a Nobel prize, but to perform at the top international level and conduct novel research that might for example lead to a paradigm shift in their field. Innovative, novel research is key for Oikos as well, and it certainly requires a high dose of creativity.

Therefore, I was really curious when I found an article by Serge Haroche, co-winner of this years’ Noble prize in physics, “The secrets of my prizewinning research“, where he tries to explain what made him a Nobel Prize winner. He gives a lot of credit to the “unique intellectual and material environment of the Kastler Brossel Laboratory at the Ecole Normale Superieure in Paris”. At this lab, he got the opportunity “to gather a permanent research group of exceptional quality, transmitting expertise and knowledge accumulated over time to successive generations of bright students.”

Other important factors he mentions are reliable financial support and European mobility programmes, “bringing expertise and scientific culture to complement our own” by opening up for visiting students and researchers. Specifically important, he argues, was “the freedom to choose our path without having to justify it with the promise of possible applications”.

Haroche also expresses an anxiety over the scarcity of resources and “the requirement to find scientific solutions to practical problems of health, energy and the environment”, that meet young scientists today. “I can only hope that they will be granted similar opportunities to those that we had: being free to choose research goals and to manage his own efforts over the long term, and able to afford the pursuit of hazardous paths before seeing the light.”

What about you, do you work in an environment stimulating Noble prize research or at least innovative, novel research that will fit in Oikos?

In the paper “From random walks to informed movement”, Emanuel Fronhofer and colleagues present a model showing that with “memorized” spatial information, an animal will boost it’s foraging success, as compared to random walk. Now on Early View.

Read Emanuel’s story about the model:

When animals move they frequently search for resources. This may, for example, be a female butterfly searching for proper host plants, a gnu exploiting grassland, or a male dragonfly searching for mating partners. Being an efficient searcher is thus an ability of great fitness implications. Indeed, movement is so fundamental to life that research on animal movement is highly relevant for many basic and applied issues.

Up to now movement is mostly modeled as a random process (random walk) and it is fascinating that such models, like the “Lévy walk”, are so capable in grasping the statistical attributes of animal movement. Yet, if we want to predict the influence of man made modifications of landscape structure on foraging success or the implications of global climatic change on animal dispersal we need a thorough understanding of the mechanisms governing movement decisions. Evidently, movement is controlled by an animal’s perception, memory, and its ability to infer the likely position of resource based on general knowledge about landscape attributes and the specific information at its hand. Further, animals should also be able to think more than one step ahead (anticipation), i.e. foresee future consequences of its moves.

Here we propose a model that accounts for all these elements (perception, memory, inference and anticipation). Our analysis shows that even a very basic implementation of these processes allows an enormous increase in foraging efficiency and results in movement patterns typical for systematic search within resource patches (e.g. of flowers of food plants; fig.1), straight movement between such patches (fig. 1) and even the emergence of foray loops (fig. 2) that have been observed in e.g. butterflies.

Our model is easily applied to insects like butterflies, wasps, or flies, searching for food or suitable plants to lay their eggs. The analysis of this model highlights the strength of mechanistic approaches to movement modeling and sets the stage for the development of more sophisticated models of perception and memory use invoked in movement decisions and dispersal. 

 

Oh, yes, fish have personalities as well! Matthew Edenbrow and his colleague has digged deeper into this to unravel the basis behind it. Now on early View: “Environmental and genetic effects shape the development of personality traits in the mangrove killifish Kryptolebias marmoratus”

Here’s Matthew’s own story:

Personality is defined as individual consistency in behaviour over time or situations. In humans it is obvious that we all differ in our personalities with some individuals being risk takers or bolder than others. While personality is clearly part of what it means to be human, there is considerable evidence suggesting that these traits are also exhibited throughout the animal kingdom. In particular, personality has been documented in several animal groups including primates, reptiles, fish and even insects, suggesting that personality is not only important but that it evolved early. At present, however, we have little insight into what factors determine individual differences in personality. Research suggests that experiences of different environments during development may underpin personality variation. In addition, growth as well as age at sexual maturity may also be important; with fast growth/early maturity suggested to generate bolder personalities. In this study we used the naturally “clonal” mangrove killifish (Kryptolebias marmoratus) as our study organism. This species is exciting because it permits us to investigate how genetically identical individuals adjust behaviour, growth and reproductive development depending upon the environment experienced. In this study we reared several genetically identical individuals in three rearing environments: 1) the presence of siblings, 2) reduced food and 3) simulated predation risk. We then investigated growth and three personality traits: exploration, boldness, and aggression, at three stages of development. Our results indicate that only individuals exposed to simulated predation risk exhibited behaviour consistency, suggesting that risk perception during early life stages is likely to be important in personality development. In addition, each of our rearing environments resulted in different growth rates and age at sexual maturity yet these differences were not key drivers of the resulting behavioural differences we observed

Now online: Perea et al. “Context-dependent fruit-frugivore interactions: partner identities and spatio-temporal variations”

Here Ramon Perea summarizes the study:

Plants are able to use animals as vectors for the dispersal of their seeds. Many fleshy fruits constitute a food attractive for different vertebrate species, that usually ingest jointly the edible pulp and the seeds, which are later defecated or brought up in suitable conditions for germination. Studies on this kind of plant-animal mutualism, called endozoochory, are numerous, but usually refer to only one pair of mutualists, or are made during one fruiting season or at only one place.

Does seed dispersal by mammals depend on the spatio-temporal context in which the interaction takes place? For instance, species abundances, specific seed crops, availability of alternative foods or vegetation structure usually change from year to year or from one habitat to another at the same locality. Many of these changing factors might affect important attributes of the plant-animal interaction. In our particular case of seed dispersal, the environmental context might modify, for example, the quantity of seeds dispersed (interaction strength) or the quality of dispersal (seed treatment, deposition on suitable sites for germination and survival, etc.), which could eventually alter the so-called sign of the interaction (from a highly successful dispersal –mutualism- to a highly unsuccessful dispersal –antagonism).

Our field work was performed in the Doñana National Park (SW Spain), under Mediterranean conditions, where we collected about 1600 faeces of a whole assemblage of fruit-eating mammals (frugivores: red fox, badger, red deer, wildboar and rabbit).  About 300,000 seeds of fruit-bearing plants were recovered of these faeces, measuring frequency of seed occurrence, plant species and seed damage for three different habitats.

For each particular fruit-frugivore pair, the interaction strength largely varied with the spatio-temporal context (year and habitat) at our local scale, leading to a low specificity across the seed-frugivore network. Frugivory and potential endozoochory should not be simply considered a mutualism leading to successful seed dispersal, but a rather variable relationship along the mutualism-antagonism continuum, depending on the ecological context.

First author Cene Fiser gives a short version of their paper “Coevolution of life history traits and morphology in female subterranean amphipods“. 

Fine-tuning evolution often requires compromises. Maximizing female’s fitness by optimization egg number and egg size to the environmental demands is a classic trade-off in evolutionary biology. But, can co-evolving morphological changes affect or even avoid this trade-off? We compared Niphargus species found in springs and in deep caves and showed that cave species are larger, stouter, have larger eggs, yet the number of eggs is not lower compared to spring species. These changes seem to be a result of decreased fluctuations of abiotic factors and of decrease in food availability in deep caves compared to springs. The environmental gradient most likely presents major source of selection that affected all herein studied morphological and life history traits. However, we have shown that the co-evolution of biological traits can modify the otherwise expected outcome of selection. We suggest that increased body size, that also enables storage of more energy, enables allocation of additional nutrients in egg size, yet the number of eggs can remain the same. Additionally, as larger eggs require better supply with water for aeration, bigger species have also modified body shape.

 

In the study “Density- and trait-mediated top–down effects modify bottom–up control of a highly endemic tropical aquatic food web” Christopher Dalton and co-workers have looked at bottom-up and top-down effects in anchialine ponds on Hawaii. Here’s Chrsitopher’s own story about the study:

For centuries, early Hawaiian residents divided land on the island into expansive parcels known as ahupuaʻa, with each ahupuaʻa containing all of the resources the residents would need to survive (water, food, shelter). Ahupuaʻa typically ran in radial lines extending from the top of the nearest volcano (Mauka; near the mountains) to the shore of the ocean (Makai; near the ocean). The expression Mauka to Makai lives on as an important model for island conservation today, emphasizing that the spectacular and unique biodiversity of these islands cannot be preserved without understanding the links between ecosystems.

Perhaps no single Hawaiian ecosystem better reflects the necessity of landscape-scale conservation as the anchialine ponds of coastal Hawaiʻi, connected through porous lava substrate to both tidal seawater and fresh groundwater. One of the most striking organism in the ponds is the endemic atyid shrimp, Halocaridina rubra (locally known as ōpaeʻula, or red shrimp).  This locally abundant invertebrate shows diel migration between daytime refuges in subterranean environments and nighttime foraging in productive surface habitats. In anchialine pools, the grazing of ōpaeʻula is often attributed a keystone function for maintaining a diverse and tuft-like epilithic crust of algae, cyanobacteria and heterotrophic bacteria.

We assess the roles of nutrients and invertebrate consumers in anchialine pond food webs by taking advantage of long-term, whole-ecosystem anthropogenic modification of bottom-up (nutrient enrichment) and top-down (grazing) controls. This study provides insight at the ecosystem scale for the interactions between top-down and bottom-up control in a system of dire need of information to direct management practices against threats from development and invasive species.

We collected quantitative samples of the epilithon quantity and composition, the abundance (day and night) of ōpaeʻula, the presence of fish and the dissolved nutrient concentrations. Sometimes this meant getting wet in the deepest pools, and sometimes it meant wading through algal and detrital mats up to half a meter deep. In the end, we captured a snapshot of the relatively simple food web structure and nutrient availability of twenty pools.

This study provides whole-ecosystem scale insight into the relative influence of bottom-up and both trait and density mediated top-down effects in pool food webs, and it also provides evidence to help guide management decisions. Our research suggests the ecological benefits of mitigating nutrient pollution are comparable to those of removing predatory, invasive fish, and monitoring these two factors can prevent the dramatic ecological change we observed in high nutrient ponds with fish.

Ultimately, preservation of Hawaiian anchialine ponds requires a perspective beyond the edges of these ecosystems. The nutrient enrichment that we observed in anchialine ponds was associated with land use (resorts, hotels and golf courses) immediately surrounding those ponds.

To truly understand and protect these hotbeds of endemism into the future, however, research must look from Mauka to Makai and assess the role of landscape context in driving change in these unique ecosystems.

Isn’t it often so that the most brilliant ideas come to us when our brains are “on holiday”, thinking of something completely different. That was the case for Ray Blick. The idea of studying networks among mistletoes and their hosts, that came during along train journey across Australia, has now resulted in a paper in Oikos, that is now online: “Dominant network interactions are not correlated with resource availability: a case study using mistletoe host interactions” by Blick et al. Ray describes what happened:

All field scientists have their peculiarities. Botanists are typically found near their transportation, unable to get past nearby plants. Ornithologist can be found walking with their eyes closed and their ear to the wind (somehow avoiding all objects in their path). And Ecologists have a spectacular ability to chop-and-change direction like a drunken person driving a car at night. I fall into the last category, where slight ‘abnormalities’ in tree shape or colour will draw my attention – Mistletoe?

 

The idea for this research originated during a ‘forced’ 1100 km train-line transect on a 16 hour journey from Sydney to Broken Hill, New South Wales, Australia. During this time the train followed a precipitation gradient traversing urban/city parks, temperate and subtropical rainforests, a wheat belt, closed Eucalypt woodlands and finally open, inconsistent sclerophyllous vegetation. All of which contained a range of mistletoe species.

 

Unable to ‘chop-and-change’ from my N = 1, ocular sampling, holiday fixed-distance, train-line transect, with an expected sleep-deprived error bias, I became interested in testing the idea that the structure of an ecological community did not have to depend on commonness. The current manuscript addresses whether host-availability, or dominance, is an important factor structuring an ecological network between a parasite and its host.    

One of the new papers online in Oikos is about the importance of full understanding of demography of wild populations for management programs. One of the authors, Eleanor Devenish-Nelson gives us here the background to the study “Demography of a carnivore, the red fox, Vulpes vulpes: what have we learnt from 70 years of published studies?”:

The successful management of wildlife depends on the ability to predict the consequences of management actions. That, in turn, often requires a good knowledge of a species’ demography and dynamics. We can use that knowledge, of issues such as birth and death rates, to produce predictive models with which we can simulate different management strategies. In situations in which we don’t know enough about a population of interest, it is common to use ‘surrogate data’ (demographic parameters from other populations of the same, or closely related, species) in order to construct predictive models.

    One species of considerable management concern is the red fox. Red foxes are widely hunted and are important hosts for several diseases. The management of red foxes is often contentious, invoking strong feelings in many people. We wanted to produce what we thought would be a straightforward model of red fox dynamics, as the foundation for answering several applied questions. At first glance, foxes appear to be well studied: a quick search brings up over 1000 papers on aspects of their demography. However, an initial assessment of that literature revealed that the demography of this widespread species was surprisingly poorly known, with limited data for most populations and, even for several better-studied populations, missing information on birth or death rates. Some of the demographic rates that we collated were highly variable between populations – but was this a result of genuine differences, or of poorly defined or presented data?

            Although the available data on red fox populations are often uncertain and frequently based on relatively short-term studies, we were able to analyse the demography of eight different populations. Those analyses revealed considerable variation in demography among the populations. Differences were sufficient to be of consequence for management. More importantly, by substituting demographic parameters between fox populations, we showed that using surrogate data could often be very misleading for managers. Data substitution is often a necessity but our analyses suggest that it can guide how managers prioritise measuring demographic parameters for their focal populations. In general, for example, a model using surrogate data on the probability with which females breed will be more misleading than if surrogate data on litter size is used. Hence, managers should prioritise accurate estimates of the former.

            Overall, what started out as a simple study revealed the significant gaps in our understanding of fox demography, especially in relation to the selection pressures this species faces, such as hunting, disease and a highly variable climate across its range. Owing to variability between populations and the dangers of using surrogate data, the need for more widespread, long-term monitoring is clear. Emerging technologies should be harnessed to make routine the widespread collection of demographic data on wildlife populations. This paper emphasises why a better understanding of the demography of fox populations is of relevance for management. 

Photo  © Paul Cecil

In the new Early View paper  “The influence of abundance on detectability” McCarthy and co-workers explore the relationship between actually being detected and being there.

Here is Michael McCarthy’s own story on the study, the paper and the results:

How hard do we need to look to be sure a species is absent when it is not detected? This question is fundamental in ecology. It is relevant when determining the appropriate level of survey effort, when compiling lists of species, when determining the extinction of species, and when developing surveillance strategies for invasive species.

Without sufficient survey effort, species are not detected perfectly. Imperfect detection arises because species may be temporarily absent, hidden from view, or simply require extra effort to find. The detectability of species can be defined by the rate at which individuals of a species (or groups of those individuals) are encountered.

Detectability of species will increase with abundance, all else being equal. But what is the nature of that relationship? We present a model of this relationship, with the rate of detection being a power function of abundance (Fig. 1). The exponent for this function (b) will equal 1 if individuals are encountered independently of one another. When clustering of individuals increases with abundance, we expect this exponent to be less than 1, but greater than 0.

As values for the scaling exponent approach 0, the detection rate becomes less sensitive to abundance (Fig. 1). Knowing how detection rate scales with abundance can assist when determining detection rates of rare species. This is important because detecting rare species is often important, yet estimates of detection rate are often most uncertain for these species. A scaling relationship would allow extrapolation of detection rates to cases when species are rare.

The field trials were conducted in a remnant of eucalypt woodland in Royal Park near The University of Melbourne searching for plants and coins, in an exotic grassland in Royal Park searching for planted Australian native species, and in eastern Australian forests searching for frogs.

Recently published in Oikos online is the paper by Carvalho et al. “Measuring fractions of beta diversity and their relationships to nestedness: a theoretical and empirical comparison of novel approaches”. Here, José Carvalho gives us the background and a summary of the paper:

Paul Jaccard proposed the well known Jaccard index of similarity in 1901. Since then the index has been used, in its (dis)similarity forms, widely by ecologists, notably in beta diversity studies. Beta diversity is one of the most broadest concepts in ecology, leading to multiple interpretations, meanings and discussions. This is probably the reason why ecologists took over more than 100 years to discover that the Jaccard index can be decomposed into two sound components of dissimilarity, replacement (turnover) and richness differences. Interestingly, after such a long time, two teams arrived independently to the same conclusions. This work represents the unification of the efforts made by the authors of both teams to elucidate others about the advantages of this approach in understanding the processes that originate beta diversity. However, the proposed decomposition is, indeed, much more general than a simple partitioning of a beta diversity measure, and applications in other fields may be expected. The generality of this approach comes from the fact that it may be viewed as the natural decomposition of a contingency table into two asymmetric components, representing the substitution of units (replacement) and differences in the number of units (richness differences).

Therefore, there is an intrinsic beauty in this approach, which comes from its generality, deep significance and remarkable simplicity.

Too much h-index around? Number of citations, h-index and journal’s impact factors are easily used statistics in evaluations of applications for academic jobs and fundings. Easy – yes. But appropriate – not really. One of our editors, Stefano Allesina (University of Chicago), has –together with two colleagues– suggested an alternative metric to use in evaluations: Future h-index, based on scientific activities, diversity of journals where papers are published, network etc. Their method was recently published in Nature.

Stefano, is this the future for academic evaluation committees?

–When I am sitting on hiring committees, I often think: “is it even possible to determine which candidates are going to be good scientists by just looking at their CVs?” To answer the question, we analyzed the career of hundreds of neuroscientists. It turns out that yes, you can pretty much forecast their future impact (i.e., predict their future h-index) using exclusively information that is contained in their CVs. What I think it’s good news is that the variables with the strongest exploratory power are basically those you would have thought they should be: current h-index, number of publications, number of publications in top journals. However, we find that the diversity of journals (and hence the size of the “audience”) is also very important. Thus, I think hiring committees should also evaluate the potential candidates for their ability to reach scientists outside their disciplines and main field of interest.

What response have you met on your method?

-There is definitely some interest, as this work adds to the heated debate on how to measure productivity in academia. However, I see the contribution as a way to skew the debate from past accomplishments toward future achievements. If anything, concentrating on the past tends to promote very conservative science, while what we need is innovation.

Isn’t this just what evaluators actually are considering, but in a non-statistical way?

-Definitely. In a way, you can read the results by saying that “science works”: what we’re telling our students to focus on — good publications — is really what matters. However, I think the emphasis on the diversity of audiences is something that is not normally fully considered by committees and funding agencies.

Can the method be used to calculate future Impact factor for journals as well?

-We found the method to be quite context-dependent. It works well on neuroscientists, when we model neuroscientists. However, the predictive power diminishes when we’re trying out-of-fit predictions in other fields. That said, I think that it could be possible to adapt the technique and extend it to journals.

Suppose you don’t have enough friends around you to do well. Then a foe shows up and takes the place of a friend. What would happen? In our paper “Competition, facilitation and the Allee effect”,  we study the dynamics of two populations with Allee effect (you need a number of friends to do well). The two populations compete (are foes) but can functionally replace members of the other population for some aspects (take the place of a friend). For example, some plants experience an Allee effect because they cannot attract enough pollinators when rare. But a competing plant species can help. So what does happen? Can you imagine that you might be completely dependent on your foe – and they on you?

Frihjof Luscher (on picture)

Lutscher’s and Iljon’s paper is now on Early View in Oikos, read more here

 

 

No excuses now, you can archive your data directly from excel files. A real snap! Here’s the link, check it out. I will try it this week too. At this point, it does not seem to provide DOIs but maybe they will.

http://dataup.cdlib.org

Perhaps we should encourage authors to archive Oikos datasets, once ms accepted, using this tool?

Apparently, they take babies too (pic from their site).

Yihaa! Finally we’re on facebook as well! Like us and get updated on new hot Oikos papers online!

http://www.facebook.com/oikosjournal

 

Nothing can spoil a vacation as efficiently as a rainfall. And nothing affects a farmer’s mood as rain- it’s presence or it’s abscence. Too much or too litte. Always an issue worth of debating.

In one of the latest Early View papers in Oikos, “Seasonal, not annual precipitation drives community productivity across ecosystems”, Todd M. P. Robinson, and co-workers study the effects of precipitation on plant production in various ecosystems.

Below, the authors give a short background to the study:

While any farmer will tell you how important it is to receive rainfall at certain times of the year, many ecological plant studies focus on how total annual rainfall affects plant production. After a meeting for the US Long Term Ecological Research Network (LTER), a group of us decided to test just how helpful it would be to focus on shorter time scales by examining whether rainfall during either the beginning, middle, or end of the growing season correlated with total aboveground production during the same season. We found that focusing on the amount of rain across one or two short time periods usually gave as much or more information on plant production as annual rainfall amounts. This was generally true across a wide array of communities from desserts to forests, despite the large difference in vegetation types and total available water.

As a graduate student working group with members from multiple institutions, we supplemented our initial LTER funded workshop by using Skype and email to coordinate our analyses and writing. As young scientists, we are excited that our cross-site analysis can contribute to the development of a more nuanced approach to plant-rainfall interactions. We expect that the combination of our work with other advances in plant-water dynamics will improve our understanding of how current and future variation in precipitation will affect plant communities.

 

Last week I attended the conference ”Innovation in Mind” here in Lund. It’s not about technical innovations per se, but more about the creative process that might lead to technical innovations. Or groundbreaking research results. Or the brilliant idea that allows you to both help people and become rich yourself. Or solve the big life problem…or other things gaining from allowing creativity to flow.

One take-home message from the meeting was a reminder about the classic importance of failures. Professor Henri Petroski, at Duke University pointed out that failures lead to success just as success often leads to failures in a kind of cyclic manner. Without failures, no progress and development.

So remember, next time your manuscript is rejected you’re one step closer to a successful accept!

And, as Petroski also pointed out – success is a bad teacher, but a good motivator. Failure on the other hand might not be a very good motivator (easy to give up…) but a very good teacher!

” fewer women than men are offered the career boost of invitation-only authorship in each of the two leading science journals”, states researcher Daniel Conley, from the Department of Geology in Lund.

Together with his colleague Johanna Stadmark he critices this gender bias in an article in Nature recently

I would be both very proud and very surprised if I could state that such discrimination does not occur at Oikos. But I’m afraid I can’t. Until recently we have however not invited researchers to write papers, so in that category of articles we dont’t have any large dataset to analyse.  I am rather convinced that our EiC for Forum papers (including some newly invited manuscripts), Dustin Marshall will be careful when inviting man after man after man in the future…

Are you convinced of your own unprejudiced mind? Check your prejudice status at this site. Many variants to choose between, but go for the most relevant one – gender and science! The test is about associations, not conscious decisions.

Cool Nature paper on how to predict success.

http://www.nature.com/nature/journal/v489/n7415/full/489201a.html

In the July issue of PNAS, Fawcett and Higginson argue, based on statistical analysis of citation rates, that a high density of equations will increase citation by theoreticians, but reduce citations by nontheoreticians even more. They advocate putting a minimum of equations in the main text, move everything else to the (online) appendix, and insert a maximum of verbal explanations of each equation.
This sounds trivial. Don’t we teach all our students to leave out unnecessary maths in presentations and manuscripts? Apparently this is easier said than done, as we still see very equation-rich papers in journals for the general ecological and evolutionary audience (such as Oikos). The reason may be that “necessity of equations” is subjective. For a thorough understanding, a full mathematical derivation seems indispensable, and hiding it from view by putting it in an appendix may also hide it from peer review. This may be good for the author (higher acceptance probability and more citations), but can be detrimental for science, and in the long run also for the author: there is nothing more terrifying for a theoretician than being confronted with an error in a derivation after publication, please let it be found during peer review!
Hence the theoretician faces a serious dilemma for which I have no full solution, only a couple of recommendations. To minimize errors, find collaborators that can check your derivations (so editors, be suspect of single author theoretical papers). A thorough verbal explanation of a model’s assumptions (and some of the derivation) may not only aid the reader, but may also advance the author’s own understanding of his/her work: when a theoretician has difficulty explaining what he/she is doing, the work is either unrealistic or incorrect. And, something Fawcett & Higginson did not analyse in detail, use simple equations: avoid Greek or curly symbols whenever possible, divide the equation in pieces where each piece has a clear meaning. Finally, when you’re really reluctant to banish your cherished formulas to an appendix, use a box. A box is really an inline appendix, and may represent the best of both worlds. Remember to think out of the box!

Rampal Etienne, SE Oikos

Each year, at the Oikos meeting, Oikos and Wiley/Blackwell together with the Per Brink Foundation, awards the Per Brink Oikos award in honor of Professor Per Brink. This year’s laureate, Prof. Tim Coulson from Imperial College London gives you below a short version of his paper entitled “Integral projections models, their construction and use in posing hypothesis in ecology”.

More about the award is found in the Editorial for the September issue 

At any point in their lives individual can be measured for a large number of characters.   These characters might be genotypes at a specific locus, age, body size, the ability to fight disease and behaviours.  Some characters might be continuous, some might be discrete.  Population level distributions of these characters can be constructed at each point in time.  Over time, a population level character distribution might change as individuals are born, die and develop.  Any population can consequently be considered as a temporally fluctuating character distribution.  Population biologists – be they life history theorists, quantitative geneticists, population geneticists or population ecologists – work with statistics that summarize aspects of the dynamics of character distributions.

Integral projection models provide a way of modeling the dynamics of character distributions.  Recently, a number of biologists including Steve Ellner, Mike Dixon, Mark Rees, Shripad Tuljapurkar, Dylan Childs, Jessica Metcalf, Peter Adler and I (to name a few), have worked on developing and applying integral projection models to address a number of questions in ecology, life history theory, micro-evolution and longer-term evolution.  A growing body of research has revealed that these models can be relatively easily parameterized for both observation and experimental laboratory and field studies, and that they can be analyzed to provide novel insight.  Given the utility of the models, many researchers, including me, believe that their use will increase in future.  For this reason I felt writing a paper showing how they can be constructed and used could be useful.  In the Per Brinck lecture I gave this year I described integral projection models, their parameterization and analysis.  The Oikos paper that accompanies this lecture develops this theme, and I hope it useful to researchers who want to learn how to construct and use integral projection models. I hope it proves of some use.

I was surprised, delighted and honoured to be awarded the 2012 Per Brinck award, and I’d like to thank the Oikos society for selecting me to receive it.  The Karlstad meeting of the Oikos society was one of the most enjoyable meetings I’ve been to, and I plan to attend many of these meetings in the future.  I do hope my paper generates some interest.

Why being a Subject Editor at Oikos? And what does it really mean? Wim van der Putten, who has been Subject Editor at Oikos for many years, and for several other journals as well, gives you his answers:

Why would you submit your research papers to Oikos and what would you expect to read in this journal? Those are key questions that each Subject Editor has to answer every time a new manuscript is ending up on the digital desk. Before that happens, however, the submitting authors had to answer the same questions, as did the Editor in Chief and the Managing Editor, and later on the anonymous referees. If somewhere in this chain a weak connection shows up, the submitted paper will not appear, at least not in Oikos. In spite of the high rejection rate at Oikos, my experience is that simply addressing these basic  why-what questions results in a balance between papers for which I proposed acceptance and rejection that comes close to the acceptance-rejection final rate of Oikos and official complaints are rare.

I am Subject Editor for Oikos since 2007. As in all journals that I was involved in as Subject, or Handling Editor, the atmosphere is nice, personal, involved, and, quite important, professional. The way how decisions are made may differ among journals. For example, in the case of the Journal of Applied Ecology, it was pivotal that the work presented should be both scientifically novel and practically applicable, which ruled out quite some submissions. On the other hand, in the case of Ecology Letters the question whether the paper presents excellent novel science that is of interest for a wide audience provides another sort of criterion and my experience is that reviewers often are quite outspoken on that issue.

My subject is terrestrial ecology, soil ecology, aboveground-belowground interactions, climate change and invasions. Quite wide and luckily I don’t get all papers in this area. All these papers get equal chance, provided that they are not narrowly focused. This may happen with for example soil ecological papers that are too obvious for specialists and not for a wider ecological audience. I think that Oikos is very suitable for soil ecological papers, provided that they are strongly conceptual. Those papers are, to my experience, very well cited in Oikos. Papers that deal with, for example, mesh sizes of soil sieving or a process in plant ecology that has already reported ten times, will not be sent out to reviewers. Also, papers that do not test clear hypotheses may not find their way through. Pleasantly, it is not too difficult to find referees, except in Summer or just before Christmas. I really don’t understand why authors submit their paper on the day before their Summer holyday starts. All potential referees may also be out for field work, hiking in the mountains, or whatsoever, which provides a hassle for the journals to find appropriate available referees.

Why would you be a Subject Editor? I see it this way. Progress in science depends on a peer review system and that depends on scientists who are willing to spend their time to handling and reviewing manuscripts for journals. When you wish to publish, but not to contribute to this process, you are capitalizing on time from others to keep the system running. That would be sort of cheating. I don’t get paid, so that my decisions will not depend on money, but on the question if I wish to make time available for this activity. The nice thing of being a Subject Editor is to send manuscripts out to who are the best experts in that field, ask their view and then weigh the outcomes. The difficulties are always in weighing contrasting views. It would be far more comfortable when all research would be published open access and I hope that we will gradually move towards that system, but there are many limitations and constraints as well.

For the near future, I hope that Oikos will be able to develop a strategy that facilitates easy availability of published work. It is very easy these days to send a request for a copy to the corresponding author, but that takes extra time and efforts, which is a real waste of money. Contents-wise, I think that Oikos is a great journal in the field of community ecology and that it might be developing even more profile into that area. Aboveground-belowground interactions and the rapidly developing area of analyzing the composition and functioning of networks in pristine ecosystems and those under (human-induced) global changes such as land use, climate change, and invasions are in my view perfect topics for Oikos and I hope to see some really great manuscripts in this area. I am ready for them!

Wim van der Putten

Here is a superb interview with Stephanie Hampton. She is the Deputy Director of NCEAS and one of the PIs on the DataOne project. Her talk at the esa 2012 meeting was very well received so I nabbed her for a chat.  The interview also includes suggestions for Oikos and journals in general. Also, she introduced me to some new terminology and thinking on the importance of data. I hope you enjoy it.

This project is cool, vibrantdata.org. Eric Berlow is one of the founders and is an ecologist with publications on food webs, interactions, alpine meadows, and the marine intertidal. This new project is bring together big data, designers, and Intel researchers to model and understand the dadta ecosystem they inhabit. Click on the research part and you will see the scope of data. Similar to the Ocean Health Index post below, this is another really nice example of ecological principles blending with social data. Here, they are using collective human input and network analysis to identify a few ‘under-nourished’ Grand Challenges for democratizing data. Wow, how can we help?

This is definitely novel synthesis. Here is the link to a really fascinating index that integrates both human and environmental condition estimates to provide a composite score of ocean health. It is also organized by public goals such as food provision, carbon storage, and provides a score for each. Canada beats Norway, Finland, and Belgium. Here is the link to the full details in Nature and the news reports.

I was wondering what ecofolks thought of this: http://bit.ly/cjlortie2. Oikos publishing a small data sample alongside each paper (when authors provide). This could be as simple as a small txt file or flat sheet showing the data structure with a few reps. Of course, an eml or link to the full dataset is preferable and should also be there, but it might be nice to at least have a little preview right there we could click on. In addition to this, we could publish a small file describing the meta-data, formally or informally, and could include a list of all factors and responses measured. This would be so fascinating. I don’t see this as impediment to full and open access to data. This would be a journal-level contribution to the process. It is also a teaser for readers to get the community wanting to see more data.

Here’s a quick interview about DataUp and how authors and journals can participate.

Here’s a great interview from today at the esa about the open sci initiatives in eeb.

The 14th International Behavioral Ecology Congress is held in Lund on August 12-17 2012. Oikos is represented at Wiley’s stand, and I will be around from time to time.

http://www.isbe2012lund.org/

If you have questions about Oikos or issues you’d like to discuss with me, send a mail and we’ll set up a meeting.

Mail to oikos@oikosoffice.lu.se

Hope to se you in Lund!

Åsa Langefors

Managing Editor

A couple of weeks ago, the Oikos Editorial Office attended the conference “Editing in the Digital World”, organized by EASE (European Association for Science Editors) in Tallinn. Apart form giving us the opportunity to explore the midevial Estonian capital, it provided us with some really productive and creative inspiration.

It was especially two plenary talks that got us going on the new digital editing world. First, Deborah Khan from BioMedCentral, London talked about “Open Access and Digital Models”. We are heading there. Sooner or later. To Open Access. Yes, Oikos as well. The questions are just how and when? Deborah made it sound much easier than we had conisdered before, giving some answers to those questions. The answer to the second question is now: A bit sooner that we had counted on… The most tricky problem to solve first is of course the financial one (it’s always about money…). Who will pay?

The second inspiring talk was held by Alan J Cann from Annals of Botany, talking about “Social Media and Academic Publishing”. And here we are! In social media! The blog is a firts step already taken, but you can soon follow us on Facebook as well. What other social media should we be at? Where do you mingle?

Oikos’ former Managing Editor, now Director of the Editorial Office, Linus Svensson and Journal of Avian Biology’s Managing Editor Johan Nilsson. Herb beers served in medivial “glasses” at olde Hansa.

Big celebration with birthday cake for EASE turning 30! In City Town Hall.

We are very proud to have our own jazzsinger in the Oikos Editorial Board. I’m talking about our Subject Editor Lonnie Aarssen, Queen University, Kingston Canada.

When not holding the microphone in his hand, Lonnie is doing research within the field of Plant Ecology and Evolution. His special interest is in the development and testing of new hypothesis and conceptual models. These interpret adaptive strategies for growth, survival and reproduction, and how these strategies affect abundance, distribution, composition, diversity and productivity.

Lonnie has also started to bring evolutionary thinking to the area of Human Affairs, giving courses where students “apply Darwinian evolutionary theory to the interpretation of culture and human nature, and how these effects impact on civilization and the challenges it faces for
the 21st century.” Sounds really thrilling and interesting to me!

Lonnie is also Editor at the realtively new journal “Ideas in Ecology and Evolution”.

Read more about Lonnie here: http://post.queensu.ca/~aarssenl/

I have an announcement to make: I am leaving the Oikos Blog and starting my own blog, Dynamic Ecology. This was a difficult decision for me, and not one I took lightly. To understand my reasons for making this decision, you first need to know something about the history of the Oikos Blog and my involvement with it.

The Oikos Blog wasn’t my idea. The first I heard of the blog was when it was announced to the editorial board by Chris Lortie, the editor who was and remains in overall charge of the blog. The initial vision was basically that it would be a group blog: all the editors would post occasionally on whatever ecological topics interested them (here is a link to Chris’ video, introducing the Oikos Blog to the world). The hope, as I understood it, was that the blog would be a new way to promote the kinds of interesting conversations and new thinking that the journal had always tried to promote. Certainly, that was my own hope. I thought the blog was a great idea, a case of Oikos thinking outside the box and recognizing the potential of a new technology. There are lots of ideas in science that are worth sharing and discussing, but aren’t best shared or discussed via formal papers, or at least not only via formal papers. Besides being valuable in its own right, I had high hopes that the blog could help encourage its readers (especially students and postdocs) to take note of the journal’s content and support the journal as authors and reviewers.

At the time, I was reading a few blogs, but I’d never thought of blogging myself. But since the journal was starting a blog, I figured it might be fun to try it out. Plus, when colleagues ask me to do something, I try to default to saying “yes”.

So I started posting. I found that I enjoyed it, I seemed to be pretty good at it, and it didn’t take much of my time. But of course, everyone has to make their own time allocation decisions, and early on Chris and I were the only editors who chose to post with any frequency. I figured other folks might start posting once we built a bit of an audience, but that hasn’t happened. To be clear, I’m not criticizing my colleagues at all for this. Again, it’s up to each of us to choose how to allocate our time. I recognize that I’ve made an unconventional choice, and also that my circumstances (I’m a tenured professor in Canada) arguably make it unusually easy for me to allocate a bit of my time to blogging. But given the choices I and my colleagues have made, I don’t feel that the Oikos Blog is serving its original intended purpose as well as it could. Rather than functioning as an extension of the journal, I think the blog has become identified with me in the minds of many readers.

Which is something I find increasingly awkward. There are topics I would like to blog about, but which I avoid because they seem inappropriate even for a journal blog as broadly-defined as the Oikos Blog. There are also some new things I’d like to try that can’t really be tried on the Oikos Blog. I’ve also found that, in my own mind, I’ve started to think of the Oikos Blog as “mine”, which it isn’t. Over time, I’ve mostly stopped connecting my posts even tangentially to Oikos journal content, which is something I tried quite hard to do early on. And if someone at Oikos or Wiley were to (quite reasonably) suggest that the blog needs to develop some sort of tighter connection to the journal, I don’t know how I’d react. Which means it’s time for me to go.

I’m tremendously grateful to Chris Lortie, Dries Bonte, Tim Benton (our previous EiC), and other folks at Oikos and Wiley for coming up with the idea for the Oikos Blog, and for trusting me to run with it essentially as I saw fit (no one ever gave me any explicit or implicit instructions on posting, or exercised any pre- or post-publication review on my posts). I hope that I lived up to their trust. My decision to leave is entirely my own and in no way reflects badly on Chris, Dries, or anyone else at Oikos or Wiley. I’ve never had anything but positive feedback and support from everyone. Chris and Dries in particular (and Tim before Dries) have been enthusiastic about my blogging, and very understanding about my decision to move on, both of which I greatly appreciate. I continue to want to see the Oikos journal do well, and I’ll continue to support the journal.

I’ll also look forward to seeing what Chris et al. do with the Oikos Blog now that I’ve gone my own way. The Oikos Blog is not ending and you should definitely keep following it; I will. I’ve made some suggestions to my Oikos colleagues on cool new directions the Oikos blog could go, and I know Chris and other folks have their own ideas. Oikos Blog is going to change, but they’re going to be good changes. Right now, the blog and the journal are pretty independent. I think they can actually be greater than the sum of their parts, and I’m very much looking forward to watching that happen.

Finally, I hope you’ll check out my new blog, Dynamic Ecology. Initially, it’s going to be quite similar to my blogging for Oikos. Almost all of my old posts and the comments on them are archived over there. I already have some new content up, and I plan to try out what I think are some cool new ideas. Thank you very  much for reading my work on Oikos Blog, I’m tremendously flattered to have such a great readership. Looking forward to seeing you over on Dynamic Ecology.

Cheers,

Jeremy Fox

Evolution 2012 is over for me, couldn’t stay for the final afternoon. Highlight of the morning was watching my students talk, of course. They all did the Fox lab proud.

I enjoyed the meeting, and got out of it what I wanted to get out of it. I wasn’t blown away by the science the way I was in 2009, probably because I had a better idea what to expect, but it was still a very good meeting. It ran very well, a big thank you to the organizers, especially Howard Rundle and Andrew Symons, who I’m sure are glad to be getting their lives back in a few hours.

Time to get back to work–about which, more soon…

 

Susan Bailey’s discovery of synonymous beneficial mutations continues to be the talk of the meeting, or at least that portion of the meeting that I hear about.

Another good day for conversations. Had a good chat with Carl Simpson, a paleontologist who’s using Price equation-type approaches to quantify species selection and major evolutionary transitions. It’s a rare treat to talk to someone about something highly technical, but who comes at it from a slightly different perspective than you. So you totally understand and appreciate each other (so don’t have to work hard to make yourself understood), and you aren’t arguing with each other, but yet you each have something new to say to the other. Got to catch up with some old friends, and was flattered by multiple people coming up to say how much they like the Oikos blog (or just to ask my opinion on stuff!)

Saw Peter and Rosemary Grant talk; I’d never seen them talk before, so that was cool. Peter began with a (better translation of) this bit of verse from Lucretius.

A good day for talks by my collaborators. Rees Kassen was very good on the genetics of adaptation in microbes, he included some meta-analytical-type results from his forthcoming book. And Dave Vasseur was very good on eco-evolutionary dynamics in a spatial context, looking at how dispersal affects spatial synchrony of population dynamics on the one hand, and local selection and local adaptation on the other.

Had dinner at the Manx with Nick Rowe, an economist here at Carleton in Ottawa and a blogger for Worthwhile Canadian Initiative. Really enjoyed chatting with Nick about everything from Darwin’s life and times to the contrasting cultures of ecology and economics to how blogging makes you a better teacher.

Last day tomorrow, I won’t be here the whole day. Just long enough to see my students’ talks in the morning. Don’t know if I’ll be able to do a wrap-up post, or whether I’ll just end up skipping straight to the big announcement…

Fairly short tonight , I’m exhausted and I need to go to bed. Indeed, my exhaustion today caused me to embarrass myself when Elisabeth Pennisi, who writes for Science, asked me some questions about the meeting. I know who she is, I read her work every week, but I was so tired I just thought she was some random well-wisher. She was asking me questions about the meeting and I was just blathering semi-coherent responses. I realized what I’d done later and sent her an apologetic email with more sensible answers to her questions. But if anyone has somehow gotten the mistaken impression from this blog that I’m the slickest science communicator around, let me be the first to disabuse you of that notion.

The talk of the day for me was the very first one I saw. Susan Bailey talked about an extraordinary and totally unexpected result that cropped up in her work on experimental evolution of Pseudomonas fluorescens. She found not one but two synonymous mutations that increase fitness, by 6-8% (a quite non-trivial increase). The result is airtight: she transformed each of these mutations into the ancestral genetic background and showed that it increased fitness, despite being synonymous. Apparently “silent” mutations need not be so silent after all! She and her lab have some ideas as to how this could possibly happen, which they’re pursuing right now. Could be something like effects on rate of transcription or something. But even as it stands, just knowing what they know, it’s the most unexpected and potentially-important result I’ve seen so far.

Saw lots of stuff on evolutionary rescue today. Models and empirical work. Some of this stuff I’ve seen before, some of it was new to me. All of the experiments seem to work exactly as predicted. Always heartening to see real organisms behaving exactly the way theory says they should.

Also saw a really nice modeling talk extending Fisher’s geometrical model to the case of a directionally-moving optimum “chased” by an evolving population.  Actually had some relevance to the evolutionary rescue work. And made some predictions that would be totally straightforward (but a massive amount of work) to test with microbial evolution experiments. And I can’t remember who gave it as it wasn’t on my schedule until the last minute, and I’m too exhausted to look it up…

My own talk was today. Far from my best performance; I threw in some spontaneous jokes that ate up too much time. So I ended up running long, and the jokes didn’t even get very big laughs. The bit at the end that got cut off was just arm-waving speculation, so it’s not as if the audience missed out on too much, but still. Running long is a pretty amateur-hour thing to do for someone who’s done as many talks as I have. Hope I didn’t disappoint any readers who showed up assuming that my talks must be as awesome as my blog. I mean, I don’t think I was terrible or anything, and some folks were nice enough  to complement me afterwards, but I hold myself to high standards and I don’t really think I lived up to them today.

It was a good day for chats in the hallways with friends and colleagues, the sorts of conversations  that cause you to miss talks you were planning to see, but that’s ok because they’re good friends and good colleagues and good conversations. That sort of thing is why I love attending meetings like this.

And several people came up today and said how much they like the Oikos blog, which was really flattering. Thanks everybody! Keep watching this space, because I’m going to have a pretty big announcement to make in a couple of days…

Greetings from Evolution 2012 in delightfully summery Ottawa. My hometown of Calgary experienced an intense hailstorm centered on my house the day before I left for the meeting. I took this as an indication that it was a good time to get out of town for a few days.

The conference center is only about a year old and it’s great. Beautiful views of the canal and Parliament Hill. Just the right size for the meeting. Very easy to get back and forth between different rooms. Many of the seminar rooms are down short little hallways and so don’t open directly onto the main gathering spaces, which is good because it minimizes the noise from conversations outside the rooms.

And there are free boxed lunches! I didn’t know lunch was included. That was like the culinary equivalent of finding money in your pocket that you didn’t know you had. 😉

p.s. In light of my deranged post about the chimes, I suppose you’re all wondering what I think of them. The answer is I don’t mind them as much as I thought I would, but I do mind them a little bit. I’d probably mind them less if they were having the intended effect more consistently. The first few talks I saw were very careful about using the chimes to time the talks as intended. But later in the day I saw many talks where one talk ended early, and so the next speaker started early, thereby defeating the purpose of the chimes. The presiders are presumably supposed to prevent this, but I think many presiders were just relying on the chimes and so not stepping in when speakers ignored the chimes. And as I expected, even when the chimes are adhered to, people are still coming in and out of the rooms while the talks are beginning and ending, simply because it takes more than 60 seconds to walk between even closely-spaced rooms. Please don’t get me wrong, I’m really enjoying the meeting, the chimes aren’t a big deal, and my opinion about the chimes is just my personal opinion. I’m sure many attendees think the chimes are great and many others don’t mind them at all.

Here are some highlights from what I saw today:

My colleague Sean Rogers did a great job summarizing his work on the genomics of ecological speciation in fishes. Very clear and very deft, compact and dense in a good way, without needing to resort to genomics jargon.

Tristan Long gave a great talk on a really clever experiment, selecting for fruit flies that can count. Yes, you can do this, apparently. You basically select for flies that, in response to an adverse stimulus, move towards a sequence of two light flashes rather than three, or three rather than four. And you have to be very careful about randomizing the properties of your flash sequences, to make sure the flies are “counting” the flashes rather than going by the total amount of time the lights are on, or the time between flashes, or the total time of the flash sequences. I envision a future in which math classes will be taught by highly evolved flies.

Anita Melnyk presented a nice series of experiments showing that Pseudomonas bacteria adapting to growth on xylose experience a more “rugged” fitness landscape than when adapting to growth on glucose. Which, as she noted briefly in the questions, is exactly the opposite of what you might have expected, given that these bacteria can metabolize glucose via two distinct biochemical pathways, but can metabolize xylose by only one. Predicting genotype-phenotype maps is hard, even for simple, well-known organisms; I’m curious if that’s something people will try to have a go at more frequently in the future.

Melanie Mueller talked about a very simple and elegant system using microbial colonizes growing on plates as a model system for studying selective sweeps in the context of populations undergoing spatial spread. Basically, it involves inoculating mixtures of different colored bacteria at a single point, and the resulting colony exhibits pretty, well-defined colored bands that change in size in predictable ways depending on the relative fitnesses of the different bacteria. Indeed, I actually wonder if the system is a little bittoo elegant, to the point of being too simple to really teach us anything new. It almost came off as engineering rather than science.

Andrew Furness talked about adaptive plasticity and bet-hedging in a really cool system, annual killifish that live in temporary ponds that dry every year. The timing of pond filling and drying is somewhat predictable (there’s a wet season, associated with reliable temperature and light cues), but somewhat unpredictable. And so as you’d expect, the fish lay diapausing eggs that initiate (and even pause!) development in response to cues, but that also develop and hatch somewhat randomly (thereby hedging their bets, rather than going “all in” in response to a possibly-unreliable cue).

Noah Ribeck explained how we’ve all been incorrectly estimating the strength of frequency-dependent selection (whoops!) The standard way to do it is to vary the initial relative frequencies of two different genotypes, then after some period of time measure their relative abundances again, and from that calculate what the selection coefficient was as a function of initial relative abundance. Which of course isn’t quite right, because you’re assuming that selection at any given initial frequency is constant over time, which it can’t possibly be in a system with frequency dependence (by definition, frequency-dependent selection coefficients change as relative abundances change). Noah derived the correct way to calculate selection coefficients for this sort of experiment, and showed that the resulting estimates differ substantially from those estimated via the usual method when frequency dependence is strong (so that relative abundances change a lot during the experiment).

Pedro Gomez did a nice poster asking how Pseudomonas fluorescens diversifies when grown under semi-natural conditions. In highly artificial lab conditions (unshaken, 6 ml batch cultures), P. fluourescens is a model system for adaptive radiation: it repeatedly diversifies into ecologically-distinct morphotypes, the two main ones being “wrinkly spreaders” and “smooths”, named for their colony morphologies when plated on agar. In nature, P. fluorescens lives in soil. And if you culture it in soil…wait for it!…it diversifies into the same frickin’ morphotypes as it does in batch cultures! Which is kind of amazing because the very specific spatial structure of batch cultures is thought to be what drives the repeatable diversification into these particular morphotypes, which occupy distinct spatial locations in batch cultures. Apparently this organism is a one trick pony! The match between the batch culture and soil diversifications is actually even tighter than that. In batch cultures you typically see a couple of different subtypes of smooths, and three or four subtypes of wrinklies–and you see all the same subtypes when you do the experment in soil! Now, it’s worth noting that in batch cultures you actually need rather specific culture conditions (e.g., specific growth medium) for the radiation to happen. And apparently those specific batch culture conditions are actually a really good analogue for this organism’s natural habitat! Who says laboratory microcosms are unrealistic?

Other notes:

“Eco-evolutionary dynamics” is hot. That kind of surprised me. I of course knew that it was hot in ecology, but I had thought that the proper evolutionary biologists would kind of dismiss it, since a fair bit of work by ecologists on “eco-evolutionary dynamics” treats the evolutionary side in kind of a weak way (a lot of it doesn’t, of course). But I’ve already seen a number of talks by people from proper evolutionary labs that sound just like the sorts of talks I’ve been seeing at the ESA meeting. Indeed, there’s a symposium on eco-evolutionary dynamics tomorrow that includes several speakers from a symposium on the same topic at the ESA meeting last year. I’m not complaining or criticizing this at all, it’s just something that surprised me a little.

Paralellism and convergence is hot. Under what circumstances is convergent evolution at the phenotypic level underpinned by the same mutations, or mutations at the same loci? But people mostly seem to be taking a case study approach to this. Maybe it’s just the brevity of the talks, but I haven’t seen any so far that have tried to place their results on this in a larger comparative or theoretical context. I don’t know, maybe we don’t yet have enough data or theory to make that worthwhile?

I saw a couple of talks on experimental bacterial evolution that pretty much came down to cross feeding (bacteria evolving to live off the metabolic waste products of other bacteria). That cross feeding evolves easily under certain culture conditions has been well-known for a long time, both experimentally and theoretically. I think it would’ve been nice to see recent work placed in the context of that literature–I wasn’t clear on if we’d learned anything really new about cross-feeding that we didn’t know before.

UPDATE: Post title corrected; it was late at night when I wrote it and for some reason I slipped into thinking I was at the ESA, where the first day of talks is always Monday.

A Canadian colleague has alerted me to a protest in Ottawa against the Canadian government’s suppression of scientific evidence, planned to coincide with the final day of Evolution 2012. Previously I’ve noted with dismay the government’s decision to cease funding the ELA; the protest organizers note that this decision can be seen as part of a larger pattern. The protest organizers (who have no connection to Evolution 2012 as far as I know) have set up a website which describes their motivation and plans. The protest will comprise a “Death of Evidence funeral procession” followed by a rally on Parliament Hill.

I emphasize that, in this as in all of my posts, I am speaking for myself, not for Oikos, its publisher, my employers, or anyone else.

I’ve talked in the past about how to network at scientific conferences–how to overcome any shyness you might have in order to talk to the people you’d like to talk to. The Evolution 2012 meeting is trying an interesting experiment on this. Poster presenters have been given the opportunity to browse the list of attendees and select a few to invite to their poster. Their chosen invitees then get an email from the conference organizers, listing the posters to which they’ve been invited and asking them to make every effort to accept the invitation.

This seems like a very creative idea to me, not something I’d ever have thought of.* I’ll be interested to see how it works out. I would think it would facilitate some interactions that wouldn’t happen otherwise. If someone looks through a list of thousands of people and invites you to their poster, that’s a bit hard to turn down (well, maybe not if you get a whole lot of invites, but I’m guessing nobody’s going to get more than a few invitations) And while some of those interactions might end up being brief or awkward–say, a student invites Dr. Famous to their poster purely as a way to meet Dr. Famous, even though Dr. Famous works on something totally different–I don’t see that as a big deal in the grand scheme of things.

On the other hand, I would encourage those who are using this system to consider whether it might not be more effective to email people personally if you really want them to come to your poster. Everyone’s busy and has lots of demands on their time. If you want someone to allocate some of their scarce time to come to your poster, it might be more effective to allocate some of your own time to sending them a personal email. Introduce yourself and your work, and briefly state why you’d like whoever you’re inviting to come to your poster. By putting in a bit of time and effort, you’re giving an “honest signal” that’s probably more likely to elicit a positive response, at least from people about my age and older.** Just a suggestion.

They’re only doing this for posters, not talks, and I think that’s the right call given that they’re trying this out for the first time. Most people already have lots of time conflicts when it comes to choosing talks, and so using the system for talks would probably result in many declined invitations. Don’t get me wrong, I think it’s great for people to invite each other to their talks, but for now that’s probably best done the old-fashioned way, via an email directly from the speaker to the invitee.

*Maybe it seems like a no-brainer to the younger generation, with their tweeps and their Bookface and their MySpace and whatnot. (MySpace is still a thing, right?) 😉

**”Old farts”

Now up at Mousetrap. Includes a contribution from yours truly. Now you know what to read on the plane to Ottawa.

Here.

I swear by the techniques in panels 1 and 2. The techniques in panels 3 and 4 are totally beyond me. 😉

It’s almost here: the biggest (~2400 attendees) evolution conference ever! I’m excited. I’ve only ever attended the evolution meeting once before, in 2009 in Idaho when it was much smaller because there were fewer societies involved. Evolution 2009 was the best conference I’ve ever attended in terms of the quality of the presentations, the standard of science on display was just incredibly high. I’m not sure how much of that was down to me knowing less about evolution than I do about ecology and so being more easily impressed than at ecology conferences, vs. me choosing talks well, vs. all the talks just being really good. But I think it was mostly the latter. So I’m psyched for this year’s iteration.

As with any big meeting (although this meeting actually seems a bit small to a regular ESA attendee like me), you can’t see everything and shouldn’t try. You need to have a focus. My focus reflects my goal to build up my currently-modest sideline of research in evolutionary ecology, using bacteria as a model system. I’m trying to identify some interesting questions I can address with experimental microbial evolution without doing genomics (as that’s still too expensive for me, and also very far from my training). I admit that it’s not entirely clear if this is still possible. One thing I took away from the 2009 meeting was that the genomics train hadn’t only left the station, it was more like a genomics rocket that was blasting into orbit, leaving people like me far behind (unless we collaborate with the people on the rocket, of course). My hope is that, even in the genomics era, there’s still a place for clever experiments describing and evolving interesting patterns of phenotypic and fitness variation across environments. The sort of experiments that would be cool to follow up with genomics–but that are also interesting in their own right.

So my focus for the meeting is experimental microbial evolution. That won’t fill my entire schedule, and so I’ll also be seeing talks by friends, a few talks by famous people who I haven’t seen speak (just to fill out my “speaker life list”), and some talks on other topics that just sound interesting. I’m also judging the student awards, so I’ve been assigned a few student talks. In order to maximize the amount of new stuff I learn, I’ll probably skip some talks by well-known folks who I think are mostly going to say things I’ve seen them say before.

I’ll also be looking to see if studies of “field model organisms” like Darwin’s finches, Caribbean anoles, and threespine stickleback are continuing to bear fruit. As David Hembry suggests,  the fact that we know so much about these organisms makes them powerful systems for asking questions that just can’t be asked elsewhere. But the fact that these systems are so famous and popular also increases the risk of bandwagony studies, and studies that just fill in minor details in a nearly-complete picture. Doing really original and important work in these systems is in some ways especially difficult, not especially easy.

So what am I going to see? I don’t have time to preview my entire schedule in detail, plus it wouldn’t necessarily be of huge interest unless your focus was similar to mine. But as a summary, I’ve scheduled pretty much everything on experimental evolution of bacteria, phage, and yeast. That includes a bunch of talks and posters from the groups of folks like Rich Lenski, Rees Kassen, Graham Bell, Mike Travisano, and others. Here are some talks on other topics that I’m planning to see, all of which should be very good, so I encourage you to check them out as well:

• Sat. 9:15, Canada Hall 2-3: Sean Rogers on Genomic approaches to studying speciation in postglacial fishes. You know how I said that genomics is taking off like a rocket? My Calgary colleague Sean Rogers is like the pilot of that rocket.
• Sat. 3:15, Canada Hall 2-3: Carl Boettiger on Detecting evolutionary regime shifts with comparative phylogenetics. Carl is super-smart, his talk at ESA last year on detecting early warnings of ecological regime shifts blew me away. Now he’s turning his attention to analogous problems in evolution. Looks like he has some really creative ideas in terms of both identifying the problem and on how to solve it.
• Sat. 3:45, Room 208: Andrew Furness on Adaptation to environmental unpredictability: phenotypic plasticity and bet-hedging in egg diapause. I think bet-hedging is cool (keep trying and failing to think of something I could do on it myself), so I want to see this.
• Sat. 4:00, Room 215: Leithen M’Gonigle on Sexual selection enables long-term coexistence despite ecological equivalence. I’m interested in coexistence, and results coming out of my own lab (see below) suggest that sexual reproduction combined with species interactions creates some novel effects on coexistence. This talk sounds like it might be broadly related. Plus, while I don’t know Dr. M’Gonigle, some of the co-authors (Sally Otto, Ulf Dieckmann) are among the best theoreticians going.
• Sun. 11:00, Canada Hall 2-3: Bronwyn Rayfield on Habitat connectivity and population dynamics in experimental networks. Bronwyn is sharp, she works with my friend and collaborator Andy Gonzalez, and like my students (see below) she works on spatial population dynamics using powerful lab-based model systems. So I really want to see this.
• Sun. 1:30, Room 201: Jeremy Fox on Local adaptation and maladaptation in space and time: aquatic bacteria as a model system. Yours truly will talk about what I think is a novel experimental approach, doing reciprocal transplants across time as well as space in order to test for local adaptation. Yes, you can do this; all you need is a “time machine” (to see what I mean you’ll have to come to the talk).  And I’ll be presenting what I think are some surprising results. And if that’s not enough incentive, there will be free beer.
• Sun. 4:00, Room 204: Ben Haller on Solving the paradox of stasis: Stabilizing selection and the limits of detection. Ben is a graduate student with Andrew Hendry. He won the “craziest thing you’ve ever done for science” thread by doing a simulation modeling study, the results of which required 2.5 billion regressions to analyze. I like to imagine Ben as Dr. Evil, putting his pinkie to his mouth and announcing that he plans to run one milllllllion regressions. Only to have a member of his committee clear his throat and whisper that one million regressions isn’t really all that impressive these days. To which Ben responds by going “Ok, two-point-five…[sidelong glance at committee member] billlllllion regressions!” (click the link if you have no idea what I’m talking about). In seriousness, this does sound like an interesting talk, independent of the whole “an-approach-so-crazy-only-a-grad-student-would-do-it” angle. 😉
• Mon. 4:30, Room 210: Dave Vasseur on Local adaptation alters the impact of spatial population synchrony. David is a good friend and collaborator, but I’d go to this even if he wasn’t either. Because David is really sharp and gives a very good talk. This is a theoretical talk on eco-evolutionary dynamics, looking at the interplay of population cycles, dispersal, and local selection. Dispersal easily synchronizes population cycles over space, which you’d think would result in temporally-fluctuating but spatially-uniform selection pressures and hence lack of local adaptation. But it’s not as simple as that, because (if I correctly recall Dave’s summary of the talk) localized selection can alter the spatial synchrony of the system. I suspect every microcosmologist who sees this is going to rush out to try to be the first to test it.
• Tue. 8:45 am, Room 203: Stephen Hausch on Diversity, coexistence, and competitive ability: The effect of intraspecific diversity on invasibility and invadability in bruchid beetles. Full disclosure: Stephen is my student (co-advised with Steve Vamosi). Full honesty: this talk is really cool. In particular, if you’re into eco-evolutionary dynamics, you need to see this. Stephen has done a massive experiment looking at how intraspecific genetic diversity affects coexistence (mutual invasibility) in two competing species of bean beetles. The effects of intraspecific genetic diversity on species coexistence is an important, under-studied, and hot topic right now; the best current thinking on how it works was the subject of a major review in TREE recently. As far as we can tell, Stephen’s results can’t be explained by any of the ideas in that review.
• Tue. 9:00, Room 203: Colin Olito on The interacting roles of foraging biology, flowering phenology and trait evolution in determining pollination network structure. After you see Stephen’s talk, just stay where you are so you can see my second student, Colin Olito. It’ll be quite different than Stephen’s talk, but equally good. It’s a modeling talk, looking at how the structure of plant-pollinator interaction networks emerges from the underlying phenologies of flowering plants and pollinators and the foraging decisions of pollinators. A novel aspect of this model is incorporating eco-evolutionary dynamics. Pollinator foraging and species’ current phenologies creates selection pressures that shift plant phenologies (e.g., to avoid competition for pollinators), which feeds back to alter the pollinator foraging and thus the selection pressures. The model builds on previous work by Devaux and Lande, who radically simplified pollinator foraging and phenology. It is quite rich and complicated (as is necessary if you want to ground your model in reality rather than in mathematical convenience), but not intractably so. For instance, you can turn off different features of the model so as to ask how they affect the model behavior, particularly the long-run plant-pollinator interaction networks structure. If you, like Colin and I, are dissatisfied with theoretical studies of interaction networks that are disconnected from real plant-pollinator interaction biology, this is the talk for you.
• Tue. 11:00, Room 203: Geoff Legault on The threshold for dispersal-induced spatial synchrony in a model system. I can only assume that, in scheduling all three of my students for the final day, the organizers were trying to save the best for last. 😉 Geoff’s talk is on the latest results from my lab on spatial synchrony of population cycles. In previous work, we’ve shown in microcosm experiments that  dispersal between habitat patches “phase locks” the predator-prey cycles in those patches, so that prey populations in different patches all cycle  in near-perfect synchrony (i.e. in phase). This strongly suggests that phase locking may explain why cyclic populations in nature often are synchronized over vast areas. But it also raises a question: how does synchrony vary as a function of dispersal rate? In theory, the effect of dispersal rate on synchrony should be highly nonlinear, basically a threshold effect: you either have enough dispersal to produce phase locking, and thus very high synchrony, or else you don’t have enough, in which case you get no synchrony at all. We did an experiment to test that prediction, the first ever done in ecology as far as we know (analogous experiments have been done in fields like neuroscience, which deals with synchrony of neuronal firing).

Presenters at Evolution 2012 know about this, but I’m not sure if all attendees do: there’s a slick app for making your personal schedule. You can access if from any browser-equipped device. Its fully searchable as well as browsable, it auto-updates if there are cancellations (nice!), it includes profiles of all presenters and attendees (you can update your own profile to add all sorts of information). It also lets you take and email notes, but  I’m guessing most attendees already have their own preferred apps for doing that.

The ESA has had a browser-based scheduling app for years, and while I think it’s still pretty good, it’s not optimized for mobile devices and lacks some of the features of the Evolution 2012 app. Might be time for the ESA to look into upgrading.

The Dependent magazine wins the internet by estimating the population density of hipsters in Vancouver, using capture-recapture methods.

If they continue sampling and build up a time series, Ted Hart at UBC can show them how to estimate past hipster abundances.

HT Jeremy Yoder.

A mix of serious and silly advice on conferences, here.

HT American Naturalist, via Twitter.

FINAL UPDATE: The snark in this post is out of line, and for that I apologize to Howard Rundle and the other Evolution 2012 organizers. It was and remains true that I’m personally skeptical of the need for the chimes, based on my own experience over many years at an even larger meeting (the ESA). But as previous updates and Howard’s comment indicate, the organizers have good reasons for wanting to try the chimes. It was wrong of me to write a snarky post based on my own gut reaction to the idea without first checking in with the organizers.

As noted by Howard, myself, and others in the comments, it’s impossible to structure a large meeting in a way that will please everyone, so the only thing you can do is try to please as many people as possible. Which is exactly what the organizers are trying to do with the chimes. The chimes are an experiment, and the organizers deserve credit for carefully considering their options and deciding to give this experiment a go.

Evolution 2012 is going to be a great meeting, chimes or not, and it’s a massive amount of work to organize. Like all the attendees, I’m very grateful to Howard and his fellow organizers for putting this meeting together. And I appreciate him taking a bit of his very scarce time to stop by and clarify the reasoning behind the chimes.

In many elementary schools, a bell sounds throughout the building to indicate the end of one class, and a few minutes later another bell sounds to indicate the start of the next class. This practice is so common it’s given rise to popular slang, such as “saved by the bell“.

I have just received an email indicating that the Evolution 2012 meeting is going to work the same way (emphasis added):

You are scheduled to give a talk at the upcoming 1^st Joint Congress on Evolutionary Biology in Ottawa. The purpose of this message is to provide some additional information about timing. All talks in the general concurrent sessions are 14 min MAXIMUM, INCLUDING QUESTIONS. A building-wide chime system will be in place to help keep all concurrent sessions on time and in synch, and to allow 1 min  movement time for attendees to switch rooms between talks (as well as time for the next speaker to get set up ). Using the building PA system, a brief start chime will be broadcast every 15 min on the hour (i.e. at xx:00, xx:15,  xx:30, xx:45), and then a 2^nd slightly different ending chime at 14 min., 29 min, 44 min. and 59 min. past the hour. For example, if your talk is at 9:00 am, then it will begin with a start chime at 9:00 am and finish with an end chime at 9:14 am. 1 min later a start chime will indicate the beginning of the next talk (9:15 am). There will be a digital  clock in each room, situated so as to be visible to both the speaker and  the volunteer chair of each session, and it will be synchronized with the chimes.

It is unclear if attendees will also require hall passes to go to the bathroom.

I’m not looking forward to having my thoughts and conversations interrupted by chimes broadcast throughout the building every 15 minutes. Even if the chimes can only be heard in the seminar rooms (which I doubt), they’ll still be incredibly annoying. And no, I don’t think it will be worth it to avoid parallel sessions drifting 30-60 seconds out of sync with one another.

UPDATE: Just to be clear, the email also says that there will be a digital clock in each room, synchronized to the chimes and visible to both the presenter and presider. So the chimes are in addition to and not a substitute for clocks!

UPDATE#2: By the way, not all talks are 15 minutes–symposium talks and presidential and award addresses are longer. So those talks are going to have chimes sounding while the talks are going on! Correction: I am informed by the meeting organizers that the chimes will not sound in rooms hosting longer talks, with the exception of a small number of longer talks being held in one particular room that is also hosting shorter talks.

Hopefully, if enough people complain early enough, they’ll shut the chimes off. Peeps: start complaining on Twitter right now (#evol2012)!

UPDATE#3: And if you say “Well, we’ll get used to it”, my responses are (i) speak for yourself! and (ii) why the frick should we have to get used to it? If someone says to you, “I’m going to cause you discomfort twice every 15 minutes for no reason,” your response should not be “Ok, go ahead, I’ll get used to it.” (Plus, are you seriously claiming you’re going to get used to chimes going off during the longer talks?)

UPDATE#4: I have corresponded with some of the meeting organizers, who were gracious enough to reply very quickly to the concerns raised in this post. They said that the chimes are a response to complaints about parallel sessions getting out of sync in past years, they will be very short (2-3 seconds) and will serve only to indicate the time (as opposed to drowning out speakers), and now that the decision’s been made to use them it would cost $4000 to turn them off. (They also suggest that the chimes will be expected and therefore less bothersome than cell phones going off, but the relevance of this fact is unclear to me. You can’t justify deciding to disturb people by pointing out that other things disturb people even more).

So the organizers clearly had their reasons, and I certainly understand that it’s now too costly for them to change their minds. And I’m very glad to hear that longer talks (mostly) won’t be interrupted. I remain unconvinced that the cure is better than the disease here, but we’ll see–perhaps I and commenter Jeremy Yoder are in a minority on this. The reaction of attendees should reveal whether most folks prefer chimes to sessions drifting slightly out of sync.

It’s not why you think. 😉

(warning: text a little NSFW)

Press release: The academic jungle: ecosystem modelling reveals why women are driven out of research. DOI: 10.1111/j.1600-0706.2012.20601.x
A large proportion of women and a growing number of men wish to work part-time in order to balance the demands of family and work.  However part-time employment in academia remains rare, and role models successfully balancing both teaching and research activities, are exceedingly rare.    There is a need to make part-time work more accessible and more viable in academia, in order to attract and retain more women in science and engineering research.   This paper identifies some of the most common and difficult issues faced by those working part-time in academia, and provides guidance about how to navigate around these.   It also identifies barriers faced by part-time academic staff which need to be addressed at a university level.

Assessing research performance of part-time staff is particularly difficult. Increasingly, research performance is assessed using metrics (such as number of papers, number of citations, h-index etc).   Application of these metrics can promote research output within an organization, however they can also undermine diversity.   In particular, research metrics are strongly biased towards full-time continuous employment, and penalize academics who take time off before becoming well established in their fields; e.g. women who part-time while raising their families.  This paper outlines the mechanisms by which metrics undermine the ability of women to participate in research if they work part-time.  This is done through an ecological analogy; just as a species is only sustainable if its population exceeds a minimum critical threshold, so too do researchers need to exceed a critical mass in order to attract more funding, students and high quality collaborators and so maintain their productivity.  In addition, the research production rate, analogous to the population birth rate, needs to exceed a critical rate if the population is to grow and survive –  these higher production rates are harder to achieve when part-time . A lower production rate is usually assumed to have a proportional effect on research outputs, but the ecological model suggests far more complex consequences on overall research productivity. If women have children before they are well established in their field, our model suggests that they will struggle to remain competitive.   This explains the observed drift of women from research to teaching, where performance is assessed on current rather than accumulated historical performance.

There are further analogies between ecosystems and universities: in both cases, diversity underpins resilience.  Optimizing a system, whether it be a forest or a faculty, to a narrow set of criteria is likely to undermine the ability of that system to respond to disturbance.   In the case of universities, over-reliance on research metrics could undermine the long-term quest for excellence by reducing the pool of talent from which our researchers are drawn.

The authors provide clear advice on how to address these issues:

• part-timers should be strategic and concentrate on either research or teaching; they need wise mentoring, and need to brave to be the “odd ones out” in a system overwhelming dominated by full-time continuous employment.
• university managers should use metrics cautiously, and implement schemes to ensure that part-time work and career breaks are not “one-way tickets” out of research.

This is pretty tangential, even for me, but I thought it might be of interest to some readers. Ecology, like many fields (including social science as well as hard science), is seeing a push towards data sharing becoming the norm rather than the exception (e.g., many leading ecology journals support the data sharing repository DataDryad). But in some areas, like politics, hard questions can be asked about whether Open Data is a good thing, or if it is a good thing, who or what it’s good for. Crooked Timber is going to be hosting a group discussion of Open Data, with a bunch of prominent and very sharp contributors, mostly from the social sciences. The focus looks like it will mostly be on Open Data in a government/politics context, but there might be something for those of you with more scientific interests. And of course, these two shade into each other, as I’m sure frequent commenter Jim Bouldin could discuss in the context of climate change politics and associated fights over access to raw climatological data.

If you can’t get enough of heavyweight intellectuals arguing about how to think about group selection, Steven Pinker has a lengthy post at The Edge, which has drawn responses from Dan Dennett and David Queller, among others (Queller’s response is particularly on point, I think).

HT Joan Strassman

 

 

I teach a graduate seminar on Darwin’s On the Origin of Species. We read and discuss the Origin and some related readings. It’s a lot of fun, for me and the students. If you haven’t yet read the Origin, or read it when you were too young to fully appreciate it, or haven’t read it in ages and don’t remember it that well, you really ought to (re-)read it. It’d be great choice for a graduate reading group–you could read a chapter a week and finish it in a semester. So here are a bunch of notes to help and encourage you to take the plunge.

Advice

• Read the first edition. Six editions of the Origin were published in Darwin’s lifetime. If you just go to a library or bookstore and pick a random copy of the Origin off the shelf, you’re probably picking up a copy of the sixth edition (if it’s got a whole chapter devoted to refuting the objections of a guy named “Mivart”, it’s the sixth edition). The sixth edition is mainly of historical interest, as the final statement of Darwin’s views. Those views were heavily revised from the first edition, in response to the many criticisms Darwin received. Unfortunately, most of those criticisms were off base, so the first edition actually is more correct than the sixth. So as a scientist who’s likely to be curious about how much Darwin got right, and who probably wants to be able to trace back modern ideas to their Darwinian roots, you’ll want to read the first edition. The first edition also is shorter, clearer, and more tightly argued, making it an easier read. It’s been aptly remarked that the sixth edition could have been titled “On the Origin of Species By Means of Natural Selection and a Whole Bunch of Other Things.” And the first edition is the edition that started the intellectual revolution–it’s the edition that changed the world. So why not read that?
• Consider which printing of the first edition you want. Darwin’s books have long since gone out of copyright, so you can read the first edition for free on various websites, such as this one. If you prefer a hard copy (and call me old fashioned, but I really think every biologist should own a hard copy), then I recommend The Annotated Origin. It’s a facsimile of the first edition, so it has the original pagination (helpful if you’ll also be reading scholarly articles about the Origin, as they all refer to the book using the original pagination). And as the title indicates, The Annotated Origin has extensive and very good marginal notes from biologist James T. Costa. This is the printing I plan to teach my class from in future. Another option, which I’ve used in my class in the past, is the famous Harvard facsimile edition first published for the Origin‘s 100th anniversary in 1959, which includes a famous and influential introduction by Ernst Mayr.
• Do a bit of background reading. The Origin is quite accessible. It’s not technical; it was written to be read by any educated person. And while the style may not be your cup of tea (though I actually like it, or at least don’t mind it), it’s not difficult reading. So you can get a lot out of the Origin without doing any background reading. But background reading can definitely help you get more out of it. I require my students to read Janet Browne’s Darwin’s Origin of Species: A Biography. It’s a short (readable in a few hours) introduction to the writing of the Origin, the social and scientific context, reaction to the book, etc. Browne’s mammoth two volume biography of Darwin is great too, but probably much more than you’d want to bite off for a reading group. And of course there are many other things you could read; it’s not for nothing that historians of science talk about the “Darwin industry”.
• Read it as part of a group. Read the Origin along with others so you can talk about your reactions as you go. Or just read along with John Whitfield, a science writer who back in 2009 did a nice series of blog posts called Blogging the Origin. He read the first edition and did a post on each chapter.

Food for thought

Here are a some suggestions for things to think about as you read the first edition of the Origin. Many of them reflect my own interests, of course, so just ignore them if you don’t share my interests. The Origin is a really rich book and there’s plenty in it for anyone.

• The quotations with which Darwin prefaces the book.  One is from William Whewell, an influential thinker of the generation prior to Darwin’s, and the other is from the “inventor of the scientific method”, Francis Bacon. Both quotes talk about how science, and scientific laws, don’t conflict with Christianity. These quotes are an attempt by Darwin not just to defend against charges of impiety or atheism, but also to defend against charges of being unscientific. At the time, the leading view on the origin of species was “special creation”, which actually had relatively little in common with the forms of creationism espoused (often in thinly-disguised form) by fundamentalists today. It’s important to understand that “special creation” was just one manifestation of the deep intellectual commitments of most senior scientists of the day. To those scientists, such as the geologist Adam Sedgwick (once a mentor of Darwin’s) the whole point of science was to read nature as the “Book of God”, to document natural order and patterns as a physical manifestation of God’s plan. To someone like Sedgwick, Darwin’s explanation for the origin of species wasn’t just wrong, it wasn’t even the sort of thing that counted as a scientific explanation at all. And conversely, Darwin argues in the Origin that “special creation” is not so much an incorrect explanation for the origin of species, as a non-explanation–it leaves all sorts of surprising patterns in nature “untouched and unexplained”. It’s difficult for a modern reader to really “get” the mindset of a special creationist, but it’s worth a try in order to understand the Origin as Darwin and his readers understood it.
  
• Darwin’s style. Note that the style is very cautious and modest (until the final, summary chapter, which is beautifully confident). Indeed, Darwin devotes a whole chapter to raising and then addressing objections to his ideas, and it’s clear from the way he writes (and from private correspondence) that he’s not just setting up straw men. He really does worry about these objections, perhaps even too much. It’s a far cry from the way most scientists write these days.
• Ordering of the material. Note that Darwin doesn’t start out with anything exotic (nothing about the Galapagos Islands, for instance, which are hardly mentioned in the book). Instead, he starts out talking about domestic animals. It’s an attempt to get readers on board, by talking about something ordinary and familiar. More broadly, note that in the first few chapters Darwin lays out his big conceptual idea–evolution by natural selection–and then in the remainder of the book discusses how that hypothesis fits with and explains the available data. One can ask, as philosopher Eliot Sober has, if Darwin wrote the Origin “backwards”. That is, he starts out with the mechanism of evolutionary change, and only then does he go on to argue for the fact of evolutionary change. Which seems a bit backwards, when put that way–shouldn’t you start by describing what needs explaining before you explain it? You may want to think about why Darwin ordered the material the way he did.
• What Darwin got right, and wrong, and the risk of mixing them up. Darwin gets a lot right in the Origin, including prefiguring almost every big idea in modern ecology (even trendy ecological ideas like biodiversity and ecosystem function!) My students are always shocked at just how much he gets right and how modern he sounds. He also gets some things wrong, of course (and not always because he was unaware of facts we’re aware of). But he gets so much right that it’s tempting to read into the Origin modern ideas that Darwin himself didn’t actually hold. Case in point: the book is infamous for not fully living up to its title because Darwin doesn’t really fully grasp how natural selection can generate new species from existing ones. That’s because he doesn’t really recognize the possibilities of spatially-varying selection (different variants favored in different locations) and frequency-dependent selection (relative fitness of different variants depends on their relative abundances). Instead, Darwin has what Costa aptly calls a “success breeds success” vision of how selection works–new, superior variants arise and then sweep to fixation everywhere they can spread to, replacing the previous variants. To get this “success breeds success” process to generate and maintain diversity, Darwin invokes what he calls his “Principle of Divergence”, which is the idea that parents will be fitter if they have divergent offspring (offspring that differ from one another in their phenotypes). The idea is basically to make the production of diversity itself a cause of evolutionary success. There are contexts in which this can work–but plenty of contexts in which it can’t (there are logical as well as empirical flaws to the idea as developed by Darwin). Now, I should note that I’m not an evolutionary biologist, and there are evolutionary biologists who read the Origin as presenting pretty much a fully-modern and correct theory of how selection affects speciation. All I can say is that I think they’re reading into the Origin, and in particular into the “Principle of Divergence”, something that just isn’t there. Read it and judge for yourself.
• Explanation and unification. It’s often said that Darwin’s great achievement in the Origin is to unify and explain many apparently-unrelated facts. The Origin links together and explains facts about everything from animal breeding to biogeography to embryonic development to the fossil record. Which raises many deep and interesting conceptual issues. For instance, is unification always a good thing in a scientific theory? Why? Is it because unification is a mark of truth? For instance, maybe unification is a sort of “indirect” or “circumstantial” evidence. If a theory seems to work well to explain facts A, B, and C, then perhaps we ought to take that as indirect or circumstantial evidence in favor of its explanation for fact D. But on the other hand, conspiracy theories also unify many apparently-unrelated facts–which is usually taken to indicate that they’re false, not true! Or maybe unifying theories are valuable because, true or not, they’re more productive as “working hypotheses”, guiding future investigations by suggesting what questions to ask and what data to collect. Darwin famously called his theory “a theory by which to work”. Then again, maybe not. For instance, progress on understanding the causes of variation and heredity (problems that famously vexed Darwin) came not just from the rediscovery of Mendel’s work, but from breaking the problem up and disunifying it. Muller and his followers figured out what we now call transmission genetics by explicitly setting aside and ignoring what we now call developmental genetics, regarding it as a separate problem. And what exactly does it mean to “explain” some fact or set of facts, anyway, and how are explanation and unification connected, if at all? For instance, do explanations have to be unifying if they’re to count as explanations at all? The intuition here is that every theory or hypothesis has to take something for granted. So if you produce a separate, independent explanation for every single thing you want to explain, then you’re effectively just changing the question, substituting one set of unexplained, taken-for-granted statements for another. At best, you’re just pushing the required explanations back a step (e.g., if you “explain” the origin of life on earth by saying “it arrived on an asteroid”, all you’ve done is change the question to “where did life on the asteroid come from?”) But if you have a unifying explanation, a single explanation for a bunch of different facts, you’re “killing many birds with one stone” and reducing the number of unexplained statements we just have to take for granted. See here and here and here for some longer posts I did on issues of explanation and unification for the class blog.
• Circular reasoning? Darwin developed his theory to explain lots of different facts about the world, and along the way he modified it in various ways as he discovered new facts. In light of that, isn’t it a bit (or even more than a bit!) circular to regard those facts as evidence for his theory, or as a test of his theory? Isn’t it circular (or maybe better, “double-dipping”) to use the facts to develop and inspire your theory, and then turn around and re-use those same facts to test the theory? After all, developing your theory so that it fits known facts guarantees that your theory will fit those facts! In philosophy of science, this is known as the “old evidence” problem: when does previously-known (“old”) evidence constitute evidence for a new theory? There are plenty of examples of the old evidence problem besides the Origin, so it’s a very general issue well worth thinking about (I emphasize I’m just throwing the issue out there as food for thought–I’m not saying whether I think Darwin’s argument is actually circular!)
• Comparative reception of the Origin. After you read the Origin, you’ll probably find yourself wanting to dig into all sorts of related topics. One related topic my class discusses is the comparative reception of the Origin in different cultures and religions. There are obvious reasons why North American and European biologists focus so much on how Christians, especially conservative ones, react to evolution. But it’s worth remembering that there are other strains of Christianity, and other religions, and it’s very interesting to compare and contrast the ways they reacted to Darwin’s ideas.
• UPDATE: Darwin is in the eye of the beholder. Darwin has been claimed as a model and even a hero by many groups. For instance, the Origin has been claimed as a biological justification for both communism and unregulated capitalism. John Whitfield astutely notes that Darwin has been claimed as a model by both the “lean and mean” school of evolutionary biology (theorists like Fisher, Hamilton, Maynard Smith, Dawkins, and Price, who focused on natural selection and its consequences using simple, elegant models) and the opposing “let a thousand flowers bloom” school (exemplified by Stephen J. Gould, with his emphasis on historical contingency and the complex interplay of many evolutionary forces). Darwin has of course been claimed as a model by naturalists, especially those who bemoan the perceived decline of field-based, observational natural history within biology. Even though Darwin himself did a lot of highly artificial greenhouse and lab experiments to which he attached great importance, wasn’t above collaborating with mathematicians (as in the section of the Origin in which he builds a geometry-based model of how honeybees can build perfectly hexagonal honeycombs), and was heavily criticized in his own time for engaging in ungrounded theoretical speculation rather than sticking close to the data and making inductive generalizations. Interestingly, many of today’s greatest naturalists, like E. O. Wilson and the Grants, achieved their greatness in a similar way, by seriously pursuing and integrating many different lines of work of which “natural history” was only one. So when you read the Origin and come to see Darwin as your hero (as you probably will!), pay attention to what you find heroic about him–it may well say more about you than it does about Darwin!

Over at Nothing in Biology Makes Sense, newly-minted PhD evolutionary biologist David Hembry reflects on the biggest changes in evolutionary biology and ecology since 2005. It’s a thoughtful piece, reflecting on some less-noted aspects of widely-noted trends. For instance, it’s not just the increasing availability of sequence data that makes synthesis and reanalysis of other people’s sequence data attractive, it’s also the fact that it’s cheap to do (particularly important in an era of rising fuel costs and increasing competition for funds). The same could be said of any database-based work, really, and also of theoretical work and laboratory microcosm work. It will be interesting to see how patterns of training, hiring, and publication shift in decades to come*, and if there aren’t frequency-dependent forces that will limit how far these directional trends can go (At some point, will really good field skills become highly prized precisely because of their scarcity, while good bioinformaticists/meta-analysts/theoreticians/programmers/etc. will be a dime a dozen?)

David also identifies some less-noted trends, such as the increasing focus of evolutionary biologists on “field model organisms” like sticklebacks and anoles, and how this poses problems of system choice for grad students who want to go on to academia. Do you choose the same model system as everyone else, thereby making it easier to ask big questions (after all, there are good reasons why sticklebacks and anoles are model systems!), but harder to stand out from the crowd? Or do you choose the road less traveled, which might make it harder to address big questions but also really impress people if you succeed? (sounds a bit like the handicap principle…)

Anyway, click through and read the whole thing.

*At least in ecology, there’s not yet much indication of a radical shift towards people publishing data collected by others.

I just tried to visit the Ecological Society of America website, and Google gave me this:

What the hell?! The diagnostic page says that over the past 90 days, a bunch of pages from esa.org resulted in malicious software being downloaded without user consent, including a bunch of exploits and trojans. I’m guessing this means the ESA website was hijacked sometime within the last few months?

UPDATE: Via the ESA Twitter feed, I see that the site was indeed hijacked within the last 24 hours. It’s been fixed, but it’ll take about 24 h for Google to recognize the fix.

As scientists, whether we’re reading a paper or listening to a talk, we often focus on the take-home message. The main conclusion. The key point. The bottom line. The gist. The summary.

But should we do that? Always?

Because the devil is in the details. And not just sometimes, but pretty much all the time. So if you don’t understand the details, if you don’t know how the “bottom line” was “calculated”, what good does it do you to know it? If you don’t know what the summary is summarizing, what’s the point of knowing the summary? Indeed, can you even be said to understand the summary?

Now, I actually think those questions have good answers–sometimes. Summaries do have their uses. There are certain times when it’s ok to ignore the details and just focus on getting the gist. But details have their uses too, and there are times when it is anything but ok to ignore them. In my experience, many of the most serious mistakes in ecology arise from insufficient attention to detail (see here and here for just two of many possible examples).

So here are some quite specific circumstances in which I think summaries have value even if you don’t know the details of what’s being summarized:

• The summary is only a starting point; you’re going to learn the details. For instance, you read the abstract of an interesting-looking paper, or read a live-tweet of a talk, and decide to go read some papers on that topic. Or, you read a bunch of abstracts, and decide to read whichever papers sound most interesting, thereby using the abstracts as a filter on what details to learn rather than as a substitute for learning the details.
• You’re only mildly interested in some topic and have no need to know very much about it.

Conversely, there are other circumstances in which you had better know the details, so that you know exactly what’s being summarized. Now, summaries are still valuable in these circumstances–but only because they help you understand the details, not as a substitute for the details.

• You’re going to work on the topic.
• You’re going to publish something on the topic.
• You’re going to apply for a grant on the topic.
• You’re going to present on the topic.
• You’re going to teach the topic.
• You’re going to cite a paper on the topic. Yes, I believe that you should read–carefully, critically, and in its entirety–every paper you cite (rule of thumb: read it as if you’re reviewing it). To cite something is to rely on it; you ought to satisfy yourself that you can rely on it. Doing otherwise is how mistakes get perpetuated. Yes, I admit to not always doing this myself. We are all sinners.

And here are some bad reasons and poor excuses for focusing on summaries to the exclusion of the underlying details:

• When reading a theoretical paper, skipping the math and any technical explanation and just focusing on the broad-brush summary, on the grounds that you don’t know math or don’t like math. No, you don’t need to rederive all the math, any more than you have to reperform every experiment you read about. But you can hardly claim to understand the math if you’ve skipped over the math entirely! Something similar could be said for any technical paper, of course, but in my experience “math phobia” is far more common than “natural history phobia” or “experimental design phobia” or “statistics phobia” or etc.
• Ignoring the details because you’re just looking for a way to get a quick paper. Many ecologists are understandably eager to find and use methods that seem easy to apply but yet promise great insight. This doesn’t just lead to bandwagons, it also leads to people rushing out to apply these methods without having thought about the details of how the methods work or how the results should be interpreted. In this context, focusing on “the bottom line” to the exclusion of details basically amounts to saying “I don’t want to have to think about this method, I just want to be able to ‘crank the handle’ and use it without thinking.”
• Ignoring the details because you think “the big picture” is what really matters. Hey, I’m a big-picture person too. I love the big picture. But if you don’t know the underlying details, then you don’t know what it’s a big picture of. You say you want to see “the forest for the trees”? Well, you’d better be able to tell if that green patch in your “big picture” (your “satellite photo”, if you will) is a forest and not grassland or farmland. Heck, you’d better be able to tell if your “big picture” is a satellite photo and not a child’s fingerpainting. (oops, that snapping sound you just heard was the sound of the whole “big picture/forest for the trees” metaphor being stretched beyond the breaking point…)

It occurs to me that this is connected to a really old post of mine on hand waving in ecology, in which I illustrated by example, but struggled to articulate, the difference between “good” and “bad” hand waving. One characteristic of good hand waving is that it starts from an appreciation of the details. When someone like Mathew Leibold argues that a very simple food web model “captures the essence” of what’s going on in some complex natural community, he’s starting from a thorough understanding of what the model assumes and what it predicts. But if you only “get the gist” of that same model, you’re in no position to judge whether it is, or is likely to, “capture the essence” of what’s going on in your study system.

p.s. Protip: if it’s not obvious where a link goes, it probably goes to something funny that’s related to the post. This is true of many of my posts.

PeerJ is a new open access publishing initiative which you join by paying a flat one-time fee, entitling you to publish as many open-access articles as you want for the rest of your life. Articles are peer reviewed for technical soundness. The initiative was founded by some serious scientific publishing bigshots.

But that’s not actually what I wanted to note. In passing, a recent Nature news article on PeerJ says that

To avoid running out of peer reviewers, every PeerJ member is required each year to review at least one paper or participate in post-publication peer review.

Hmm, wonder where I’ve heard that idea before? Wait, it’ll come to me…

p.s. Just to be clear, I’m not claiming that PeerJ got this idea from Owen Petchey and I. I just feel vindicated that something like our “PubCreds” idea would be incorporated into a serious publishing business venture. More than one, actually. This also vindicates a remark which scholarly publishing consultant Joseph Esposito made to me at a publishing conference: PubCreds will happen when someone figures out how to monetize it (or in this case, monetize a larger initiative, of which something like PubCreds is one component).

Here’s an intriguing little cognitive psychology experiment, which shows that highly educated people evaluate the truth or falsehood of statements less quickly and less accurately if those statements are ones that appear true under a “naive” theory, but which education teaches us are actually false (e.g., “Humans are descended from chimpanzees”, “The Earth revolves around the sun.”). This suggests that pre-existing false ideas aren’t “overwritten” by education, they’re merely “suppressed”.

I wonder if something similar can explain the persistence of certain zombie ideas. Is it just inherently difficult to unlearn the first thing we ever learn about a topic, as I suggested in this old post? So that, if the first idea you ever learn about a topic is false (say, you’re taught the IDH as an undergrad), you become a zombie and it becomes very difficult to cure you? And if so, what can we do about it (besides make sure that our undergrad curricula are up to date)?

Presumably there’s a lot of research on this I’m not aware of.

p.s. Depressingly, rates of correct responses were lowest, and speed of response slowest, for questions about evolution (questions fell into 10 different subject areas across the physical and life sciences).

UPDATE: Error in first paragraph now fixed.

The Ecological Society of America is encouraging bloggers to blog the ESA meeting. If you do a post on any aspect of the meeting, they’ll create a post on their EcoTone blog with your post title, an excerpt, and a link back to the full post on your blog. Details here.

Interesting idea. I’ll need to ask a few questions before I participate. Not sure if my daily previews and summaries of my experiences are the sort of thing they’re looking for. Those posts are really informal, and they’re written for the audience of this blog rather than the much broader audience of EcoTone. Plus, I sometimes include criticism of various aspects of the meeting. Even if EcoTone is just going to be doing brief excerpts and linkbacks, I want to make sure they’re ok with what they’re linking to.

And if you’re tweeting the meeting, the hashtag is #ESA2012.

Elinor Ostrom, the first woman ever awarded the Nobel Prize in Economics, has died. Ecologists, including me, mostly don’t know her work (I only know of it). But we should. She did hugely important work on the management of common pool resources, and argued that Hardin’s tragedy of the commons was in fact sustainably soluble (and, as a matter of historical fact, had been sustainably solved many times) via appropriate social norms and institutions, not just by privatizing the commons as Hardin argued.

Crooked Timber has a brief remembrance and (as always over there) a remarkably good comment thread full of thoughtful remarks and useful links.

 

I lived in Ottawa for four months a couple of years ago while on sabbatical. I’ve drawn on that experience to create an annotated map of suggested places to eat and drink for Evolution 2012.

Basically, everyone is going to be eating and drinking in the Byward Market area, as it’s the highest concentration of bars and restaurants close to the convention center and to major tourist attractions like Parliament. I’ve suggested a few places in that area, but also some places a bit further afield for folks who like to walk or who are willing to bike/drive/take a taxi. The other “main drags” in downtown Ottawa are Elgin St. and Bank St.

Bottom line: the best places to drink in Ottawa are The Manx (walkable from the convention center; hidden in a basement; great cozy, buzzy atmosphere; excellent, changing food menu; really popular) and Pub Italia (not walkable; has the only world-class beer selection in Ottawa; big draft list plus hundreds of bottles including lots of rarities and obscure Belgians; an essential stop for beer geeks like me).

See also this list of local pubs produced by the meeting organizers.

Over at Sociobiology Joan Strassman has a great post on how to choose talks at big conferences like the ESA Annual Meeting. This is something we’ve talked about on this blog before, but no one ever brought up Joan’s excellent suggestion: have a focus. That is, try to see as many talks as you can in a particular area that you want to learn more about. This is a great way to get up to speed on the current state of play in that area.

 

Patterns and processes of population dynamics with fluctuating habitat size by Fukaya K (Hokaido University, Japan), Shirotori W and Kawai M.

Competitive outcomes between two exotic invaders are modified by direct and indirect effects of a native conifer by Metlen KL (Nature Conservancy, Oregon, USA), Aschehoug ET and Callaway RM

Soon as Early View!

  Hi everybody

My name is Åsa Langefors, I’m the new Managing Editor at Oikos. After the two initial  months at the office, I have now started to learn the routines and to get aquainted with editors, authors and reviewers. i.e. with Oikos. And just as things started to  find their place in my brain, we switched over to ScholarOne for handling of manuscripts. New stuff to learn, new routines etc. But the new system has so far run smoothly and I hope everybody will have some patience for possible confusions that might arise in the beginning.

I have my background in Molecular Ecology, having studied MHC-genes in fish as a PhD-student and post-doc. During the last five years, I have combined a career as a freelance journalist with work at the university in a research school in Genomic Ecology (with a special interest in so called soft skills, including carreer development, personal development, how to deal with gender issues etc.) and in a EU-project in Soil Ecology. I am sure that several parts of my quite mosaic background will be useful in my work with Oikos.

When not working, I spend time with my family, consisting of a husband and two kids and also a lot of time in my garden. In addition, when life is good, I think we have a duty to enjoy it. So, good cappuciono, fine wine, good food, doing workout (preferentially outdoors, like running, walking, skiing or skating) are important matters to me.

A rant against live-tweeting talks, here.

I don’t tweet at all, so I don’t live-tweet. In particular, I don’t feel like I’d provide much of value to anyone by live-tweeting talks, or that I’d get a lot of value out of following others’ live tweets.* And while it doesn’t bother me much as a speaker–I just ignore people who are doing it, much as I ignore undergrads who text during class–I can understand how it would bug some people.

I do agree with the linked post that those who do it get less out of the talk. In particular, I try to make my talks as dense and fast-paced as possible without risking losing the audience. That is, I try to design my talks so that you have to pay close attention, and so that your close attention is rewarded. You’ll hopefully feel like you really got a lot out of the time you spent listening to me. I question whether you’ll be able to fully follow a talk, especially the sort of talk I try to give, if you’re live-tweeting. Studies show that even people who think they’re good at “multi-tasking” and have practiced it a lot actually aren’t good at it, by any measure.

So live-tweeting doesn’t really bother or offend me personally, though I can see why it would offend others. I think the people who do it are mostly hurting themselves, if only a little, and not for much benefit that I can see. But I’m an old guy, so I suspect some of our regular commenters are totally going to disagree with me on this.

UPDATE: Just to be clear, I certainly don’t think that the only people who ever pay less-than-full attention to a talk are the people who are live-tweeting. Far from it. And as a speaker, I personally am no more bothered by live-tweeters than I am by people who aren’t paying full attention for some other reason.

UPDATE #2: Perhaps not surprisingly, I’m not big on the way this post is being summarized on Twitter. The post isn’t really about whether “talks should be ‘tweetable'”, it’s about the benefits and costs of live-tweeting them. Anything is ‘tweetable’. But in truth, this probably says more about me than it does about Twitter or folks who use it. I tend to distrust other people’s short summaries of anything, whether tweeted or not. And just for the record, let me say that commenters here, and Joan Strassman in her own post, have articulated some good reasons why one might live-tweet (or tweet right after a talk), or follow the live-tweets of others. So while I personally still don’t see much value in live-tweeting, I can understand why others do. As with many things in life, it’s a question of doing what works for you.

*To be clear, I do see value in many other uses of Twitter.

I continue to find Zen Faulke’s “fighty crab” meme hilarious. I’m still realizing how versatile it is.

Written a confusing blog post? Fighty crab tells you:

Want to celebrate World Oceans Day? Fighty crab tells you how:

Want to win your One True Love back (assuming your One True Love was having a dalliance with, um, dolphins)? Fighty crab has you covered:

p.s. I didn’t come up with any of these.

Zen Faulkes (‘Neurodojo‘) has compiled his many excellent blog posts on scientific presentation tips into a short e-book (i.e. a pdf file). Recommended.

Billiards is all about sequences of causal events. Your cue strikes the cue ball, causing it to roll into another ball, causing that ball to roll into the corner pocket.

Falling dominoes are sequences of causal events. You knock over the first domino, which knocks over the second, which knocks over the third.

Rube Goldberg machines are sequences of causal events. The toy car is pushed into a line of dominoes, the last of which falls onto another toy car, which rolls down a ramp and runs into a ball, which rolls down another ramp…[skipping ahead]…which causes a piano to fall…[skipping some more]…which causes paintball guns to fire at a rock band.*

When humans think about causality, they find it natural to think in terms of sequences of events. That’s why colliding billiard balls are a paradigmatic example of causality in philosophy.

But ecology is mostly not like billiards, or falling dominoes, or Rube Goldberg machines. Like history, ecology is (mostly) not “just one damned thing after another.” But it’s hard not to think of it that way, and to teach our students not to think of it that way.

(UPDATE: I’m not saying that ecology, or dynamical systems in general, aren’t causal systems. They are! I’m just saying that the nature of that causality is such that it’s misleading to think about it as “Event A causes event B which causes event C which causes event D…”)

(UPDATE#2: Nor am I saying that ecological systems are “nonlinear” or “nonadditive”. They are, but that’s not my point here. For instance, you can have a sequence of causal events in which the magnitude of the effect is nonlinearly related to the magnitude of the cause. See the linked post from Nick Rowe, below, for further clarification. Sorry the original post wasn’t better, it’s clear that I did a lousy job of anticipating the ways in which readers might misunderstand what I’m trying to get at here).

Ecology is about dynamical systems. Stocks and flows, not falling dominoes. Inputs and outputs, not colliding billiard balls. Simultaneity, not sequences. Feedbacks, not one-way traffic.

Here’s an example. It’s a population ecology example, but not because population ecology is the only bit of ecology that’s about dynamical systems. It’s just a bit of ecology I know well. I could equally well have picked an example from physiological ecology (e.g., to do with individual growth), or from community ecology, or from ecosystem ecology, or from island biogeography, or conservation biology, or spatial ecology, or macroecology, or etc.

The example is predator-prey dynamics. You’ve got some prey that reproduce and die, and some of those deaths are due to predators. Predators convert consumed prey into new predators, and they die. Purely for the sake of simplicity (because it doesn’t affect my argument at all), let’s say it’s a closed, deterministic, well-mixed system with no population structure or evolution or anything like that, so we can describe the dynamics with just two coupled equations, one for prey dynamics and one for predator dynamics. And again for the sake of simplicity, let’s say it’s a constant environment and there’s no particular time at which organisms reproduce or die (e.g., there’s no “mating season”), so reproduction and mortality are always happening, albeit at per-capita and total rates that may vary over time as prey and predator abundances vary.

You cannot think about this dynamical system in terms of sequences of causal events. For instance, let’s say the system is at equilibrium, meaning that predator and prey abundances aren’t changing over time. That does not mean nothing’s happening! In fact, there’s a lot happening. At every instant in time, prey are being born, and prey are dying, and those two rates are precisely equal in magnitude but opposite in sign. And at every instant in time, predators are being born and predators are dying, and those two rates are precisely equal in magnitude but opposite in sign. Inputs and outputs are in balance. You cannot think about equilibria in terms of sequences of causal events, it’s like trying to think about smells in terms of their colors, or bricks in terms of their love of Mozart. What “sequence of events” keeps the system in equilibrium?

Or, let’s say the predators and prey exhibit cyclic dynamics. For concreteness, let’s say it’s a limit cycle in the Rosenzweig-MacArthur model. Why do the predators and prey cycle? This is a case where it’s sooo tempting to think in terms of sequences of events; I know because my undergrad students do it every year. “The prey go up, which causes the predators to go up, which causes the prey to crash, which causes the predators to crash.” In lecture, even I’ve been known to slip and fall back on talking this way, and when I do the students’ eyes light up because it “clicks” with them, they feel like they “get” it, they find it natural to think that way. And it’s wrong. Not “wrong in the details, but basically right”. Not “slightly wrong, but close enough.” Wrong. Births and deaths are happening instantly and continuously. There are no sequences of events here.

Now I can hear some of you saying, ok, that’s true of the math we use to describe the world, but it’s not literally true of the real world. In the real world one could in principle write down, in temporal order of occurrence, all the individual birth and death events in both species. But my point would still hold. A prey individual was born, which caused prey abundance to increase by one, which caused…what, exactly? What’s the next domino to fall in the sequence? Another prey birth? No. A prey death? No. A predator birth or death? No. What that increase in prey abundance did was slightly change the expected time until the next birth or death event, by increasing prey abundance and (in any reasonable model) feeding back to slightly change the per-capita probabilities per unit time of giving birth and dying. Now, you could try to drill down even further, down to the underlying physiological (or whatever) causes of individual births and deaths, and the underlying mechanisms linking per-capita birth and death probabilities to species’ abundances. But you’re never going to find something that lets you redescribe predator-prey dynamics in terms of sequences of events, each causing the next. (UPDATE #3: And to clarify further, no, I’m not trying to argue against the notion that population dynamics are ultimately a matter of individual organisms giving birth, dying, and moving around. I actually heartily believe that! My point is to do with how to interpret the causality of what’s going on, whatever level of organization (individuals or populations) we choose to focus on.)

Our deep-seated tendency to think in terms of causal sequences of events rather than in terms of rates of inputs and outputs (i.e. rates at which the amount of something increases or decreases) doesn’t just make it hard to teach ecology. I think it also makes it hard for professionals to do ecology. For instance, to preview a future post, much of the appeal and popularity of structural equation models (SEMs) that they let researchers take causal diagrams (variables connected by arrows indicating which ones causally affect which others) and turn them directly into fitted statistical models. That is, SEMs mesh with and reinforce our natural tendency to think about causality in terms of colliding billiard balls. Which I think makes them positively misleading in many circumstances (as I say, much more on SEMs in a future post).

This post was inspired by a post on the same topic by Nick Rowe. Nick’s post is about economics. His post is way better than mine. You should click through and read it (no training in economics required; stop when you get to the bit at the end about “concrete steppes”, which is where the post segues into technical economics issues).

*Click the link to see what I’m talking about. 😉

The current distribution of species bears the strong stamp of “big, slow” historical events and processes–speciation events, continental drift, meteor strikes, ice ages, the rises and falls of mountain ranges and land bridges, etc. Which has often been taken to imply that, in the grand scheme of things, the sorts of “small, fast” processes that contemporary  community ecologists study don’t actually matter all that much.

In this old post, I argue that, to the contrary, “big, slow” historical processes only matter if contemporary community ecology lets them matter. What we ought to be asking is not whether community ecology is “important” (because it has to be), but why community ecology is “history preserving” rather than “history erasing”.

Intrigued? Click through and read the whole thing.

p.s. I know I said in a recent post that I was done talking about macroecology for a while. But the response to that post was so positive that I changed my mind. It’s gonna be all macroecology all the time now! (just kidding)

Here’s what it probably feels like for a strawberry flower to be pollinated and develop into a strawberry. With cartoons.

“The changes can be unsettling.” LOL!

HT Jeremy Yoder

Note: This post is old wine in a new bottle. It basically repeats some old posts, just in a slightly different way. I’m only doing it because the comment threads on those old posts are really good, but I felt like they petered out a bit too soon.* This is my attempt to revive them. So if you’ve been reading my old posts on macroecology and the associated comments and thinking “More please!”, this post is for you. But if, as is more likely, you’ve been reading those old posts and thinking, “Jeebus, doesn’t he have anything new to say?”, just skip this one.

Note: Man, this post ended up way longer than I originally intended! Sorry about that. Maybe everybody should skip it. Basically, all the post does is argue that macroecology is not at all like astronomy, except in a couple of superficial ways. If you really care why I argue that, and can’t guess it from having read old posts, read on…

***********************

I write a lot on this blog about how difficult it is to infer process from pattern, mechanism from observation, and causation from correlation, even tentatively. In response, ‘macroecological’ colleagues, whose work emphasizes the documentation and interpretation of observed ‘large-scale’ ecological patterns, often point to the example of astronomy. The example of astronomy, they say, illustrates how observational science can be successful science, and even causation-inferring science.

But unless I’ve missed it (which is quite possible), they never keep following that line of thought, at least not in any detail. I wish they would. Yes, absolutely, astronomy is a successful, causation-inferring science, and it does so without being able to manipulate stars or galaxies or whatever. But precisely how does it achieve its successes? After all, there are also unsuccessful observational sciences. Macroeconomists, for instance, infamously remain in vociferous disagreement on even the most basic points. So what makes astronomy successful, and can macroecology emulate it? I emphasize that in asking this question, I really don’t know the answer and I’m genuinely curious. I’ve asked this question in the comments on previous posts, but never gotten a reply. So I decided to do a post on it, in the hopes of smoking out Brian McGill and Ethan White’s inner astronomers. 😉

Just so I don’t come off as totally lazy (“Hey readers, teach me astronomy!”), I did do a bit of background research**, the fruits of which are below.

Origins of the macroecology-astronomy analogy

The macroecology-astronomy analogy seems to originate from a comment by Robert MacArthur to Jim Brown, reported in Brown’s Macroecology (p. 21):

“Astronomy was a respected, rigorous science long before ecology was, but Copernicus and Galileo never moved a star.”

Brown goes on to cite geology, specifically the theory of plate tectonics, as a second example. That mechanistic theory is well-confirmed even though geologists have never experimentally manipulated entire tectonic plates or the mantle plumes that move them around.

Brian Maurer, in his Untangling Ecological Complexity: The Macroscopic Perspective (p. 112-113) pursues this analogy a little bit further (in fact, as far as I’ve ever seen it pursued):

“Explaining these patterns [in assemblages of species] is difficult because the standard tools of science for developing mechanistic explanations cannot be used. With few exceptions, there is no way to manipulate the biodiversity of a large geographic region. Another problem is that often the same pattern might be consistent with more than one process…[These limitations] also apply to astronomy, but this has not prevented astronomers from learning a great deal about stars and galaxies. Astronomy has a strong, quantitative theoretical foundation in physics, and this foundation allows fairly precise predictions to be made about what patterns can be expected in complex systems like galaxies.”

I can totally see why early macroecological texts pushed this analogy. It’s an effective response to anyone who would claim that, if you’re not doing manipulative experiments, you can’t possibly be doing science. But while the analogy establishes the possibility of a successful, astronomy-like macroecology, I don’t know that it establishes the actuality. Indeed, based on what little I know about astronomy, I’m skeptical of the ability of macroecology to emulate astronomy. I don’t think this means macroecology can’t be successful or infer causality–but I do think its methods aren’t really analogous to those used in astronomy. But these thoughts are tentative. I hope that people who know more than I do about astronomy (or macroecology!) will chime in.

I emphasize that I’m not actually saying that any macroecologist takes the astronomy analogy as seriously as I’m about to try to take it. Nor am I saying that they should have done so–I’m not accusing them of failing to follow their own argument to its logical conclusion or anything like that. I’m actually not out to criticize their use of the analogy at all. I’m just intrigued and curious. I want to see what we can learn by pushing the analogy as far as it will go, even if that means pushing it further than macroecologists have ever taken it.

Reasons why macroecology is not like astronomy

1. Ecologists can do experiments! Ok, it’s true that you can’t manipulate, say, the biodiversity of an entire continent. But you certainly can do smaller-scale experiments that are directly relevant to interpreting large-scale patterns. One example that I’ve raised before, and which I’ll raise again because it’s such a great example***, is the work of Jon Shurin on local-regional richness relationships in freshwater zooplankton communities (Shurin 2000, Shurin et al. 2000). After correcting for an artifact to do with variation in spatial extent of different regions, lake zooplankton appear to exhibit a linear relationship between local (within-lake) species richness, and regional richness (total richness of all lakes in a large region). This has been taken to indicate that local diversity just reflects dispersal limitation, a sort of “passive sampling” from the regional “species pool”, meaning that local communities are open to colonization by whatever species happen to arrive. But here’s the thing: local zooplankton communities aren’t open. You can directly test that by trying to invade lakes with species not currently present. It turns out that invasions mostly fail, unless you first drastically reduce the densities of resident species, thereby eliminating competition from residents. Far from being open to whatever colonists happen to arrive, lakes are almost completely “saturated”. This means that linear local-regional richness relationships had been misinterpreted. As is now well-established, linear local-regional richness relationships are one of those patterns that are, as Maurer says, “consistent with more than one process”. Small-scale experiments like Jon’s were key to establishing that point in the context of local-regional richness relationships.

So macroecologists can’t “manipulate the stars” or “manipulate tectonic plates”–but they certainly can do experiments that provide information directly relevant to the macroecological equivalents of the heliocentric theory or continental drift. In this respect, macroecologists are actually in a better position than astronomers or geologists when it comes to inferring causality. They have more weapons in their arsenal.

This is one way in which I think the analogy with astronomy might actually be holding macroecology back a bit. Their emphasis on the impossibility of large-scale, “manipulate the stars”-type experiments sometimes seems to cause them to downplay the relevance of other sorts of manipulations.**** Just because the pattern is large-scale doesn’t mean the only relevant experiments are large-scale. The underlying processes that putatively generated the pattern typically operate everywhere, at all times, and so can be tested for anywhere, at any time.

As a second example, Jon Levine and others have powerfully combined small-scale experiments with larger-scale observations to  show that the large-scale correlation between native and non-native species richness is down to the fact that the same environmental conditions that promote native diversity promote non-native diversity (e.g., high rates of propagule supply). This effect swamps the fact that, all else being equal, more species-rich communities are more resistant to colonization by species not already present (Levine 2000, Levine 2001 Oikos)

Now in fairness, Ethan White has argued in the comments on old posts that all the best macroecology actually recognizes this and is based on synthesis of all relevant information, including small-scale experiments. I wish I fully shared his confidence that this kind of work is what everybody is out to do, at least ideally. I’m torn between taking his word for it (since he knows the literature far better than me), and my own admittedly-limited experience as a reviewer of macroecological papers which too often neglect directly-relevant experimental work.

2. Astronomy is based on the quantitative estimation of different effects, using well-developed and -validated physical theory. My point here is basically an expansion on Brian Maurer’s brief remark about astronomy’s “strong, quantitative foundation in theoretical physics.” What that foundation allows astronomers to do is to estimate and subtract out from their observations the effects of all sorts of “nuisance” factors and sources of error, leaving them with accurate, precise estimates of the quantities of interest. For instance, see here, here, and here for layman-level discussion of how “transits”, such as the recent transit of Venus between the Sun and the Earth, allow astronomers to accurately and precisely estimate quantities like the mass of the Sun, the absolute (not just relative) distances from the Earth to other objects in the solar system, and the chemical composition of the atmospheres of other planets. See here for the estimation of stellar parallax (a very subtle effect). And see here for discussion of how subtle deviations in the orbits of planets from what would be predicted based on Newtonian mechanics and the masses of known planets led to the discovery of new planets. Note in every case that getting a good estimate does not involve just accumulating a big sample size and then averaging away the “noise”, thereby allowing the desired “signal” to reveal itself. Rather, getting a good estimate involves using well-established,quantitative background knowledge to precisely quantify, say, the Doppler shift in the spectrogram of the atmosphere of Venus due to the Earth’s movement around the Sun.

Macroecologists certainly try to do this sort of thing. They often include covariates in their statistical analyses to statistically control particular sources of variation, they can use comparisons among different datasets to estimate error sources known to affect only some of those datasets, and they can use randomization-based “null models” to try to figure out what their data would look like in the absence of some particular process like interspecific competition. But are those approaches anything like as precise and well-validated as what astronomers do? Indeed, in the case of randomization-based null models, there are reasonable arguments that they don’t, and can’t, work at all.

Further, macroecologists often deny that we could ever have fully-parameterized models of the “microscale” processes of birth, death, and dispersal that ultimately drive species distribution and abundance. I actually don’t think that’s true, at least not universally, but let’s say for the sake of argument that it is. Doesn’t that amount to a denial that we’ll ever have a “strong, quantitative foundation” that would allow us to estimate and subtract out “nuisance” effects, thereby allowing us to precisely estimate effects of interest? For instance, if you think that it’s impossible to parameterize a many-species competition model for a large, spatially-heterogeneous area, what makes you so sure that just randomizing your observed species x sites matrix while holding the row and column totals constant subtracts out all effects of interspecific competition while leaving effects of all other processes intact? Isn’t that basically like an astronomer saying “I don’t know how to quantify the Doppler shift in my spectrogram, so I’ll just randomize my data with respect to the day of observation and hope that that fixes it?” Doesn’t this lack of what economists call “microfoundations” make macroecology more like macroeconomics than astronomy?

3. Astronomy isn’t really about statistical patterns. In a classic Oikos paper I discussed in one of my first posts, John Lawton (1999) argues that macroecological patterns reflect the fact that, at large scales, the “noise” of species- and system-specific details “averages out”. There are reasons to question whether that’s a good analogy for macroecology, but let’s accept it for the sake of argument. Here’s my question: is astronomy like that? I mean, when astronomers estimate the properties of some object in outer space–its distance from us, its chemical composition, its size, etc.–they’re estimating the properties of that particular object. Yes, they do that repeatedly for lots of objects, and I’m sure there are statistical patterns in the resulting data. For instance, maybe the “species-abundance” distribution of different kinds of stars has some sort of interesting shape? But it’s my impression that most (all?) of the vaunted quantitative, cause-inferring rigor of astronomy comes into play in estimating the properties of individual objects, not in studying the statistical features of collections of objects. Basically, I’m suggesting that, if statistical mechanics is your model for what macroecology is like (as both John Lawton and, in other passages in his book, Brian Maurer suggest), then astronomy is not. Astronomy and statistical mechanics are very different in terms of what they’re aiming to do and how they’re aiming to do it. In his paper, John imagines a fairy who foolishly tries to understand the intractable random movements of individual particles of a gas, totally missing the tractable macroscopic properties of large collections of gas particles. But predicting the highly non-random movements of individual “particles”–planets, say, or comets–is what astronomers live for!

Am I totally wrong about all this? Maybe I’m just focusing on the wrong bits of astronomy, and other bits actually are a great model for how macroecology works, or could work? Or maybe I’ve just shown that the whole macroecology-astronomy analogy can’t be pushed any further than the very short distance that Brown and Maurer push it? (Woohoo! I’ve saved macroecology from a shaky analogy no one would’ve thought of if I hadn’t suggested it!) Or in pushing the analogy further, have we actually highlighted some things that needed highlighting, such as the ability of macroecology to draw on small-scale experimental data? I’m honestly not sure–you tell me.

And then I promise to shut up about macroecology and talk about something else. 😉

*Also, right now I’m a bit low on both time for really substantive posts, and really new things to write substantive posts about. It’s quicker to repeat myself. 😉

**Specifically, I spent 5 minutes googling “astronomy blog” and reading the top hits. 😉

***I did warn you about old wine in a new bottle.

****It also causes them to forget that you can “manipulate the stars” if you create an artificial universe in which the stars are small enough to be manipulable. That is, you can do experimental macroecology in microcosms. Phil Warren and his collaborators have done a lot of nice work on this (e.g., Holt et al. 2002).

Now up at the world’s most popular evolutionary blog, Pharyngula. Check it out.

Commenting on the previous post, Jim Bouldin notes that people often choose, or justify, their methods on the basis that those methods have been used by many others in the past.

As Jim points out, there is a problem with this:

You should choose well-justified methods, not popular ones. And you should justify your methods by justifying them. Saying that “At least I’m only making mistakes that others have made before” is not a justification.

By the way, I’m guilty of invoking past practice as a justification for my own practice, though I try to do it only as a supplement to good justifications rather than as a substitute. Occasionally referees who aren’t swayed by good arguments can be swayed by bad ones, so I sometimes use both.

I’m all for making the most of the data we already have–but no more than that. An hazard of trying to wring as much as possible from any dataset is that you’ll overstep and try to use the data to address questions or draw conclusions that can’t be addressed or drawn. In ecology, this was the motivation behind the excellent NutNet project-existing data weren’t really adequate, so they had to go collect new data.

Over at Cop in the Hood there’s a fun rant by Peter Moskos on just this point, in a social science context. A huge, information-rich Big Dataset recently was used to argue that people in poor neighborhoods have just as easy access to nutritious food as people in rich neighborhoods, so lack of easy access to nutritious food can’t explain higher incidence of obesity in poor neighborhoods. Which is total bunk because the data on what constitutes a “grocery store” are, if not total garbage, at least totally inadequate for the purpose for which this study tried to use them. A fact which the study recognizd, only to dismiss it with the excuse that better data would have been difficult and expensive to obtain. Which amounts to saying “Doing it right would’ve been hard, so we decided to do it badly.” Click through to read the whole thing, it’s a great, short read and not at all technical.

I’m curious to hear from readers who work more with pre-existing data than I do: Have you ever looked into doing some sort of analysis of pre-existing data, only to drop it because you decided that the data weren’t good enough? Or have you ever reviewed a synthetic paper and told the authors, “Sorry, but your whole project is worthless because the data just aren’t good enough”?

And are there any general strategies that can be used to guard against making more of the data than is reasonable? One possibility is to  involve the people who collected the data in any synthetic effort using those data. That’s certainly something my CIEE working group on plankton dynamics did, and I think it was a good thing, even if it does have its own risks (e.g., causing the synthesizer to worry about truly minor flaws in the data that don’t actually affect the results).

Note that one strategy that doesn’t guard against poor-quality data is “make sure you have a really big dataset.” Having more fundamentally-flawed numbers, or more non-flawed numbers to go with the fundamentally-flawed ones, doesn’t make the fundamentally-flawed numbers any less flawed. Put another way, flaws in your data don’t just create “noise” from which a “signal” can be extracted if only you have enough data. Flaws in your data can eliminate the signal entirely, or worse, generate false signals (as in the social science study linked above).

It’s only natural that someone like me would worry about this sort of thing, as I don’t work with pre-existing data that much. I’d be interested to hear from people who do data synthesis for a living and are really invested in it (the ‘synthesis ecologists‘). How often do you run into serious problems with data quality, bad enough to prevent you from answering the question you want to answer? Does the possibility keep you up at night? What do you do about it?

HT Andrew Gelman, who also comments.

p.s. Before anyone points this out in the comments: I freely grant that everyone always tries to push every method or approach as far as it will go, so everyone always runs the risk of overstepping what their chosen method or approach can teach them. But ‘synthesis ecology’ is what’s hot right now, so that’s the context in which I think it’s most important to raise this issue.

UPDATE: Here’s this post in cartoon form.

The summer conference season is upon us. I’ll be at Evolution 2012 in Ottawa and the ESA Annual Meeting in Portland, Oregon (where I’m talking on Thursday afternoon…sigh).*

Closer to the meetings, I’ll have meeting previews highlighting talks I’m especially looking forward to attending, and places I’m planning on eating and drinking, and I’ll be blogging from the meetings as well.

In the meantime, here are a couple of posts from the archives to help you prepare:

• Choosing which talks to attend is always tricky at a big meeting. Which raises the question: Are there any reliable predictors of talk quality? (besides “Jeremy Fox recommended this talk.”)
• Here are a bunch of tips on how to give a good talk, and avoid some common statistical errors. Also includes links to more comprehensive sources of advice on giving talks.
• If you’re giving a poster, here’s my one big piece of advice: YOUR POSTER HAS TOO MUCH FRICKIN’ TEXT! I know this because EVERYONE’S posters have too much text these days. Seriously, I’m not kidding. A poster is not a paper in large, colorful, flat form. No one wants to stand there reading for 15 minutes. Your poster should be a highly digested, mostly graphical summary of your work. All the text can just be short bullet points, and not many of them (like, say, 3 for the Discussion). After all, you’re going to be standing right there–if people have questions, they can ask you! In all seriousness, posters were actually much better before the advent of color plotters. It was a pain in the neck to print out and matte a whole bunch of 8.5 x 11 sheets of paper, so you pared things down to only the essential information.
• Here’s how to ask tough questions, and here’s how to answer them.
• Here’s why to “network” at conferences, and here are some tips on how to do it.

*And while I won’t be there, I’m a co-author on a talk at the Society for Vertebrate Paleontology Annual Meeting. It’s on using the Price equation to separate effects of speciation, extinction, immigration, and within-lineage change on mammalian size evolution, and includes an illustrative application to a classic paleo dataset. Check it out if you’re going!

I find it a little challenging and often distasteful that the top hits for some ecological journals, including Oikos, are the publisher’s page of it. Often, I want to get right to the journal, imagine that, and it is tough to navigate through the publisher standard page to get to it. I recently enjoyed a really exciting paper in Seed Science Research, so googled it, and got the publisher page. I wanted to post a comment on a paper I read there. After skimming the page, http://journals.cambridge.org/action/displayJournal?jid=SSR, I found the ‘SSR home’ link on the left.  Whew. I clicked it assuming I was going to get a nice home-spun page with the feel of the journal and instead I get the exact same page again.  Now, let’s try Oikos.  I googled and it and got the following return, http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1600-0706, that is after after the yogurt sponsored ad (we should pay to displace that really). Whilst this is an attractive url, I propose we get the Oikos/Nordic one higher up on the list. Or perhaps move the content there or ask for a clearer redirect? I skim now, find the ‘journal home’ on the left, click it, and viola… get the same page again. OK, maybe I am misunderstanding it. Where is the Oikos, Nordic Society homespun page? I can’t see it. Backing out, I google Nordic Society, and whilst I am happy to see the Canadian one at the top, no Oikos again. The Nordic Soc of Irish Dancers is the most fun one though. As a final test of my secret hypothesis here that we are not managing our online presence as ecologist as best we could, I try the journal of ecology. First hit, gorgeous, www.journalofecology.org/. The url makes sense, photos pretty, nice screen, I can see it is the BES in the top right without it dominating the journal presence, and if I work at it, I can see at the very bottom that it is a Wiley publication. Better.  If someone has time, check a few more journals for us but part of making ecology more funded, better perceived, and useful, has to include more effective online perception.

Some forthcoming (in press) Oikos papers that caught my eye. Lots of good stuff in the pipeline!*

Nadeem and Lele introduce a new maximum likelihood-based method of population viability analysis (PVA) and test it on song sparrow time series data. The new method, called “data cloning”, was previously developed by Lele in other contexts. It estimates observation error as well as process error (e.g., demographic stochasticity), and deals gracefully with missing data. The clever thing about it is that it has all the computational advantages of more popular Bayesian estimation methods, but it’s fully frequentist and so doesn’t need priors. Which is a good thing because priors for the rare, poorly-known species for which we often want to construct PVAs often are pretty arbitrary guesses which have strong effect on the outcome of the analysis because there’s not enough data to “swamp” them. You also avoid having to adopt the subjectivist Bayesian interpretation of what your probabilities (e.g., extinction probabilities) mean. In the case of song sparrows, it turns out that incorporating observation error into the analysis really changes the results. The approach is even sensitive enough to detect evidence that the data and associated PVA model omit important biological processes (here, dispersal).

Tielbörger et al. use a massive series of carefully-controlled common garden experiments to reveal strong evidence for “bet-hedging” germination in annual plants. Roughly, bet-hedging is a way of maximizing your expected relative fitness in an uncertain environment. Germinating all your seeds every year (going “all in” in betting parlance) provides a big payoff if the year turns out to be a good one, but it is very risky. If the year turns out to be a bad one, all the resulting plants will die before reproducing (the ecological equivalent of “going bust”). But conversely, if you never germinate any seeds, so that your seeds just sit in the ground, they’ll eventually all die without reproducing (“nothing ventured, nothing gained”). So the optimal germination fraction (the one with the highest expected relative fitness compared to the others) will be some intermediate fraction, the precise value of which depends on the probability distribution of different kinds of years. That’s the theory, anyway. But strong empirical tests are almost non-existent, because they’re really difficult. For instance, you have to control for environmental and genotype x environment variation in germination fraction. The authors went to the trouble of developing inbred lines of each of three annual plant species, growing up their seeds in a common greenhouse environment to eliminate maternal effects, and then planting those seeds into common gardens along a rainfall predictability gradient in the field, and along an artificial rainfall gradient in the greenhouse. As expected, species subject to higher risk of reproductive failure exhibit lower genetically-determined germination fractions. Yes, Virginia, annual plants really do hedge their bets–and those that face more risk do more hedging!

Fraker and Lutbeg develop an individual-based model of mobile predators and prey and show how limitations to the movement rates and perception distances of individuals cause their spatial distributions to deviate from the ideal free distribution. If you have limited information (=limited perception distance) and limited ability to act on that information (=limited movement rate), you can’t attain the ideal free distribution (which assumes that you have perfect information which you’re free and fully able to act upon). Which at that level is kind of obvious, but Fraker and Lutbeg explore precisely how the resulting distributions deviate from ideal free, which is much less obvious. Bailey and McCauley (2009) is one nice experimental paper showing data illustrating some of the predicted consequences of limited information and movement rates. More broadly, I always like stuff that shows the complex and counterintuitive macroscale consequences of different microscale assumptions about the behavior and movement of individual organisms. Maybe if people write enough of these kinds of papers, other people will quit trying to infer the underlying microscale processes directly from inspection of (or some sort of randomization of) macroscale data.

Speaking of starting from microscale assumptions and deriving their macroscale consequences, Casas and McCauley ask: What’s the functional response of a predator that must divide its time between searching for prey, and other activities (broadly denoted as “handling”)? If you said “It’s an increasing saturating function and we’ve known that since Holling (1959),” you’re right–sort of. That is, you’re right only if you’re prepared to make radical simplifying assumptions about the relative timescales of the underlying processes that cause predator individuals to change “states” (here, from the state of “searching for prey” to the state of “handling captured prey” and back again). If you want to avoid such radical (and often unrealistic) assumptions, then you have to be prepared to do much more complicated math, which Casas and McCauley illustrate for both parasitoids and a predator (Mantis, the same predator considered by Holling himself in a classic 1966 study of predator functional responses). One consequence of increased realism is that the predator population never reaches an equilibrium or stationary distribution of individuals in different states, a fact which turns out to have important and testable consequences for predator-prey dynamics.

Finally, I don’t see how I can get away without mentioning Mata et al., an impressively large protist microcosm experiment manipulating disturbance intensity, disturbance frequency, nutrient enrichment, and propagule pressure in factorial fashion and examining their effects on resident community structure and invader success. As you’d expect, such a complicated experiment throws up complicated results, some of which seem to be readily interpretable (e.g., high disturbance intensity creates conditions that favor invaders with high intrinsic rates of increase), others less so. I do think it’s a little unfortunate that the authors frame their experiment as a test of Huston’s “dynamic equilibrium model”, since that “model” shares the same fatal logical flaws as zombie ideas about the intermediate disturbance hypothesis. I suggest that framing the experiment in terms of logically-valid theory might have aided interpretation, and possibly even suggested a somewhat different experimental design.

Many other interesting-looking papers coming out, but I don’t have time to dig into all of them so this’ll have to do for now. Happy reading!

*p.s. Just so you know, no one has ever told me, hinted to me, or implied to me that I should promote the journal’s content. When I highlight Oikos papers that I think are particularly interesting, it’s because I think they’re particularly interesting. It’s not like I ever think “Ok, gotta pick some Oikos papers to talk up now.” I hope you’ll take my word on that, given that I also link to a lot of non-Oikos content and criticize Oikos papers. Don’t get me wrong, I’m an Oikos editor and author, I like the journal, I want to see it do well and continue to fill what I think is an increasingly crucial niche, and I think the blog can help achieve that. And so when I do highlight interesting papers, I highlight interesting Oikos papers. But if I didn’t think there was anything worth highlighting, I wouldn’t. So I hope you find it valuable if I occasionally highlight Oikos papers I find particularly interesting, or invite the authors to do so, just like I hope you find the other posts valuable. But if for whatever reason you don’t, that’s fine.

Note as well that in saying this, I mean no criticism of any other journal blog, many of which focus much more than we do on the content of the associated journal. Different blogs are different.

During a long and interesting post on storytelling in science, Andrew Gelman makes the following remark about some famous statisticians and the techniques they’ve developed:

The many useful contributions of a good statistical consultant, or collaborator, will often be attributed to the statistician’s methods or philosophy rather than to the artful efforts of the statistician himself or herself…Rubin wielding a posterior distribution is a powerful thing, as is Efron with a permutation test or Pearl with a graphical model, and I believe that (a) all three can be helping people solve real scientific problems, and (b) it is natural for their collaborators to attribute some of these researchers’ creativity to their methods.

I think this is right. Techniques and approaches, statistical or otherwise, aren’t powerful except in narrow and, in the grand scheme of things, rather unimportant senses. If techniques were really what mattered, science could be reduced to a recipe that anyone could follow.* What matters most, I think, is how and to what the technique is applied, and how the results are interpreted and linked to other evidence and ideas. None of that can be automated or routinized. Which means that what really matters is the ability of the scientist using the technique or approach. Rich Lenski wielding a vial of bacteria is a powerful thing, as is Mathew Leibold with a simple food web model, or Jon Losos with a phylogeny, or Tony Ives with an autoregression, or Peter Morin with a jar of protists, or me Steven Frank with the Price equation.

It remains to be seen if “me wielding zombie jokes” turns out to be powerful. 😉 If it does, this is what I’m going to say. 😉

*Francis Bacon thought this was possible (“But the course I propose for the discovery of sciences is such as leaves but little to the acuteness and strength of wits, but places all wits and understandings nearly on a level.”) There’s much that he got right in “The New Organon” (1620), but I think this bit is wrong.

The editorial describing and announcing future endeavors is now open access. Whew. We intend to offer all future editorials similarly.Thanks for your patience.

Here’s a rare problem, but one that raises some interesting issues: What’s the appropriate way to deal with a crackpot at a scientific meeting? Specifically, a crackpot presenter? Over at Doing Good Science, Janet Stemwedel raises this question in the context of a philosophical talk that was nominally about the non-crackpot topic of abductive reasoning but actually propounded conspiracy theories about the Kennedy assassination. Janet raises a number of interesting issues, some of which I’ve also blogged about, such as the ethics of tough questions (is it impolite to tell someone they’re full of it, or impolite not to?) and some of which I probably should (e.g., Do scientists have an ethical obligation to use some of their finite time to correct mistakes by others, even if those others seem unlikely to recognize the error of their ways? What are the risks to being too quick to dismiss off-the-wall ideas?*)

As I said, crackpot presentations are rare, especially in ecology. I have the impression crackpots are more attracted to other fields, like philosophy, fundamental physics, and mathematics.** I’ve never actually seen a crackpot ecology presentation. I have seen one ESA talk that literally made no sense, but it was by someone who wasn’t an ecologist by training and who had done competent work in his own field, and so was merely seriously confused rather than a crackpot.

Have you ever seen a crackpot presentation at an ecology meeting? If so, what did you, or the other audience members, do?

*There certainly are examples in ecology and evolution of off-the-wall ideas being quickly dismissed when they shouldn’t have been. The Price equation is one. George Price was brilliant, but he had at least strong crackpot tendencies. Nature famously had to be tricked into reviewing his initial paper on the Price equation, and Richard Lewontin initially dismissed the Price equation as trivial before changing his mind and writing to Price to apologize for his initial dismissal. And conversely, there are examples of crackpot ideas not being recognized as crackpot when they should have been. Recently, PNAS found an excuse to retract a crackpot paper on speciation by hybridization that was backed by Lynn Margulis, an eminent scientist who late in her career pushed her ideas to crackpot extremes. The line between crackpot and non-crackpot ideas, and between crackpots and non-crackpots, isn’t always easy to everyone to see.

**Well, I guess climate change denialism could be considered an example of crackpot ecology, but that’s not so much crackpot as political. I tend to think of true crackpots as being crackpots for their own idiosyncratic reasons.

FOOB Chris Klausmeier recently sent me a 1962 Ecology paper by Robert McIntosh.* Here’s the first paragraph:

Thomas Henry Huxley once commented, “Life is too short to occupy oneself with the slaying of the slain more than once” (Huxley 1901). Certain ideas seem to be invulnerable to attack and persist although subjected to multiple executions. One such ecological idea is that the “law of frequency” devised by Raunkiaer (1918, 1934) is useful as a simple indication of uniformity or homogeneity within a stand or between several stands of vegetation. The persistence in current sources of a concept which has been belabored by ecologists for 40 years is a testimonial to the tenacity of ideas.

Robert McIntosh: long-ago zombie slayer!

I take heart from the fact that no one talks about the “law of frequency” any more. Zombie slaying is possible! But clearly it takes a while–apparently several decades, in the case of law of frequency. Which, perhaps not surprisingly, is longer than a typical professional career. A famous line from Max Planck is relevant here…

The Thomas Henry Huxley quote with which McIntosh leads his paper is interesting, in that Huxley could hardly be said to have lived by it.

By the way, any reader who is inspired by this post to try to revive the “law of frequency” just to mess with me, be warned: You are not big, you are not clever, and I swear to the God of your choice that I will kick your a**! 😉

*Chris has so far not revealed how the heck he found this…

Don’t tell me none of your collaborations are like this.

Ecology is complicated. Anything we might want to measure is affected by lots of different factors. As a researcher, how do you deal with that?

One way to deal with it is to try to focus on the most important factors. Try to “capture the essence” of what’s going on. Focus on developing an understanding of the “big picture” that’s “robust” to secondary details (meaning that the big picture would basically look and behave the same way, no matter what the secondary details). This is how I once would have justified my own interest in, say, simple theoretical food web models (e.g., Leibold 1996). Sure, they’re a caricature of any real-world system. But a caricature is a recognizable—indeed, hyper-recognizable—portrait. The whole point of a caricature is to emphasize the most important or distinctive features of the subject. A caricature that’s not recognizable, that’s not basically correct, is a very poor caricature.

But here’s a problem I’ve wondered about on and off for a long time: what’s the difference between a simplification that “captures the essence” of a more complex reality, and one that only appears to do so, but actually just gives the right answer for the wrong reasons? After all, as ecologists we aren’t in the position of an artist drawing a caricature. We don’t know for sure what our subject actually looks like, though of course we have some idea. So it’s not obvious that our caricatures are instantly-recongizable likenesses of whatever bit of nature we’re trying to caricature.

Now, one possible response to this concern is to deny that getting the right answer for the wrong reasons is even a possibility. If we develop a simplified picture of how the world works, then any omitted details which don’t change the predictions are surely unimportant, right? If our model makes basically the right predictions, then it’s basically right, at least as far as we can tell? Right?

I’m not so sure. The reason why I worry about this is what philosophers call “overdetermination“. Overdetermination is when some event or state of affairs has multiple causes, any one of which might be sufficient on its own to bring about that event or state of affairs, and perhaps none of which is necessary. Philosophers, at least the few I’ve read, are fond of silly examples like Sherlock Holmes shooting Moriarty at the exact same instant as Moriarity is struck by lightning, leaving it unclear what caused Moriarty’s death. But non-silly examples abound in ecology. Here’s one from theoretical ecology (I could easily have picked an empirical example). The Rosenzweig-MacArthur predator-prey model predicts predator-prey cycles for some parameter values. Imagine adding into this model a time lag between predator consumption of prey and predator reproduction, one which is sufficient on its own to cause predator-prey cycles. Now here’s the question: is the original Rosenzweig-MacArthur model a good approximation that “captures the essence” of why predator-prey cycles occur when there’s also a time lag? Put another way, is the original Rosenzweig-MacArthur model “robust” to violation of its assumption of no time lags? Or in this more complex situation, is the Rosenzweig-MacArthur model misleading, a bad caricature rather than a good one?

The same questions arise when different causal factors generate opposing effects rather than the same effect, and so cancel one another out. Consider a predator-prey model which has a stable equilibrium because of density-dependent prey growth. Now add in both predator interference and a time lagged predator numerical response, with the net effect being that the system still has a stable equilibrium because the stabilizing predator density-dependence due to interference cancels out the destabilizing time lag. Does the original model “capture the essence” of the more complex situation? Is it “robust” to those added complications? Or is it just giving the right answer for the wrong reasons?

I think the answer to all these questions is “no”. That is, in cases of overdetermination, I’d deny that a model that omits some causal factors is “capturing the essence”, or is “robust”, or is accurately “caricaturing” what’s really going on, no matter if its predictions are accurate or not. But I’d also deny that, in cases of overdetermination, a model that omits some causal factors is misleading or wrong. That is, I think that the alternative possibilities I set up at the beginning—our simplified picture is either “basically right” or “basically wrong—aren’t the only possibilities. There’s at least one other possibility—our simplified picture can be right in some respects but wrong in others.

Further, I think this third possibility, though it might seem rather obvious, actually has some interesting implications. For one thing, a lot of work in ecology really does aim to “capture the essence” of some complicated situation. It’s not just theoreticians who try to do this—empirical ecologists (community ecologists especially) are always on the lookout for tools and approaches that will summarize or “capture the essence” of some complex phenomenon. Which assumes that there is an essence to be captured. Conversely, a lot of criticism of such work argues not only that ecology is too complicated to have an essence to be captured, but that all details are essential, so that omitting any detail is a misleading distortion. I’m suggesting that, at least in an overdetermined world (which our world surely is), both points of view are somewhat misplaced.

For another thing, it’s important to recognize how simplified pictures that are right in some respects but wrong in others can help us build up to more complicated and correct pictures of how our complex, overdetermined world works. Recall my examples of predator-prey models. How is that we know that, say, density-dependence is stabilizing, while a type II predator functional response and a time-lagged numerical response are destabilizing? Basically, it’s by doing “controlled experiments”. If you compare the behavior of a model lacking, say, density-dependence to that of an otherwise-identical model with density-dependence, you’ll find that the latter model is more stable. In general, you build up an understanding of a complicated situation by studying what happens in simpler, “control” situations (often called “limiting cases” by theoreticians). The same approach even works, though is admittedly more difficult to apply, if the effects of a given factor are context dependent (this just means your “controlled experiments” are going to give you “interaction terms” as well as “main effects”). So when I see it argued (as I have, more than once) that complex, overdetermined systems can’t be understood via such a “reductionist” approach, I admit I get confused. I mean, how else are you supposed to figure out how an overdetermined system works? How else are you supposed to figure out not only what causal factors are at work, but what effect each of them has, except by doing these sorts of “controlled experiments”? I mean, I suppose you can black box the entire system and just describe its behavior purely statistically/phenomenologically. For some purposes that will be totally fine, even essential (see this old post for discussion), but for other purposes it’s tantamount to just throwing up your hands and giving up.

Deliberately simplifying by omitting relevant causal factors is useful even when doing so doesn’t “capture the essence”, and even when there is no “essence” to capture. These sorts of simplifications aren’t caricatures so much as steps on a stairway. In a world without escalators and elevators, the only way to get from the ground floor to the penthouse is by going up the stairs, one step at a time.

You end up making a terrible sandwich.

(I know that’s not really the take-home message of the linked post. But it was the best teaser line I could come up with to encourage you to click through and read the whole, hilarious thing).

Just discovered The Thesis Whisperer, a blog by Inger Mewburn, who studies research student experiences. It looks to be quite honest, thoughtful, and funny, and has quite the following (most posts get dozens of comments, which puts this blog in the shade). Worth checking out, especially if you’re struggling to write your thesis and need a boost from reading about others in the same boat.

Not to say I agree with all of it. There’s a recent post comparing thesis writing to a marathon, which is a superficially-plausible but bad analogy for reasons Thomas Basbøll lays out.

I’ve been running into lots of bad analogies lately, based on identifying two totally different things based on one superficial similarity. Might have to post on this at some point…

Invited ms due in a few days, too busy to post, so here’s a video of a cockatiel singing “Rock Lobster” by the B-52s:

We want to welcome authors, referees, and the board to the manuscript central platform used by many journals. It is our hope that this will increase speed, efficiency, and communication for the journal. I will miss the old system in some respects, but please do not hesitate to email the editor(s) when you review or submit as we hope to continue building a community here, not just a journal.

Previous system…

Oikos has a new EiC, Dries Bonte.  In an editorial, this and other major developments are described including some of the new philosophy and current goals for Oikos.

Dries in action… likely calling authors to tell them the good news.

Here is a brief summary of the changes (but I leave the thunder to the editorial).
The editorial team, inclusively, will write editorials as frequently as we can to highlight papers illustrating effective synthesis.
Oikos is moving all handling to ScholarOne Manuscripts to speed things up and ensure that reviews are never lost.
There are now 50 handling editors and profiles (including some amusing pics) are listed on the Oikos website.
Currently, Oikos publishes approximately 15% of all submissions.
As a first examplar of insights into Oikos synthesis, the spatial ecology papers in that issue are described highlighting the novel elements.

Science is full of debates. Some are productive, some aren’t. What makes for a productive debate?

First, a few remarks about what I mean by a “productive” debate. I don’t mean a debate that leads to agreement on all or even any points, either among the main participants or among non-participants. For instance, consider a debate on some matter of empirical fact. If round-earthers and flat-earthers debate the shape of the Earth, and eventually agree that it’s flat (or “compromise” and agree the Earth is hemispherical), does that make their debate productive? I’m not saying that one side or the other is always right, or that compromise positions are never right, merely that resolution of any sort is not a marker of a productive debate. Now, it’s always unproductive if participants can’t agree on what questions they’re debating.* But there are lots of reasons why a debate might fail to settle on an agreed resolution, and being “unproductive” is only one of those reasons.

What I mean by a productive debate is a debate in which the participants engage with one another, meaning that they pay close attention to and understand the other side, and respond to the other side’s evidence and arguments rather than strategically ignoring them. A productive debate also is one in which all relevant evidence and argument gets fully aired, and arguments are pursued to their logical conclusions and their full implications considered. A productive debate also is one that doesn’t get sidetracked by misunderstandings. This means that the participants need to choose their words carefully and precisely, be clear and explicit, and expect the same from other participants. A productive debate also is one in which no one engages in personal attacks, and in which no one takes criticism of anyone’s views (no matter how strong) to be a personal attack.** Productive debates may not reach an agreed resolution—but if they don’t, they at least make the issues crystal-clear. That clarification of the issues is both a very useful outcome (especially to students and others learning for the first time about the subject of the debate), and the most that can be expected.

By that standard, there are lots of productive debates in ecology. Recent debates over MaxEnt, aired in part in Oikos, are an excellent example. Debates over “sampling effects” in biodiversity-ecosystem function research, sparked in part by an Oikos paper (Aarssen 1997), led to productive development of new experimental designs and statistical techniques that resolved the issue (Loreau et al. 2001). The big debate over ratio-dependent functional responses eventually led to agreement on some issues and “agreement to disagree” on others (Abrams and Ginzburg 2000).***

Actually, probably most “tit for tat” exchanges of comments in the literature are productive by my standard. After all, that’s what “tit for tat” means—you raise a point, and I respond to it rather than ignoring it or dodging it. Indeed, there’s a productive debate in ecology every time reviewers do a good job reviewing a ms and the authors respond. Of course, in such cases there’s an editor involved, who effectively can force both sides to debate productively, on pain of having their comment go unpublished, their review ignored, or their ms rejected. 😉

Notably, in the examples I listed where the protagonists eventually came to partial or complete agreement, this was only after a lengthy period of vociferous disagreement. If you are the sort of person who wants to see agreement at the end of a debate (like my fellow editor Dustin), well, I think you can only get that, if at all, by first letting the debate run its natural, debate-y course.

Which isn’t to say all debates in ecology and evolution are productive. The recent spat over inclusive fitness in evolutionary biology hasn’t, as far as I can tell, raised any issues that weren’t already familiar, and seems if anything to have muddied the waters rather than clarifying them. Further back, while I don’t know the punctuated equilibrium literature well, my impression is that that debate had both productive and unproductive elements. Productive in that it sparked interest in some important issues and prompted some new empirical research. Unproductive in that it proved difficult for the protagonists to agree on the questions at issue, and on what would count as an answer. IIRC, the punctuationists were rather shifty and difficult to pin down on what exactly they were claiming, and the same data were infamously interpreted as evidence for and against punctuated equilibrium by the opposing sides.

Anyway, that’s what I would argue. Who wants to debate me? 😉

*It’s fine, and often necessary, to debate the choice and framing of the question, and what counts as evidence for a given answer. But at some point, all sides do need to come to an agreement as to what questions are at issue and what would count as an answer if debate is to be productive.

**Which means, among other things, that “politeness” can be the enemy of productive debate, if by “politeness” you mean “not saying exactly what you mean, in order to avoid possibly offending someone.” That’s not what I mean by “politeness”. In my view, empirical evidence and logical argument are never impolite, and if anyone else takes them that way, that’s their problem. This doesn’t mean you can’t try to phrase what you have to say in a polite way, but you can’t do so at the expense of clarity and explicitness if you really want to have a productive debate.

***Note to youngsters: yes, there once was a massive debate in ecology over a particular functional response model.

The Canadian federal government recently announced that it will no longer fund the renowned Experimental Lakes Area. There is now an effort underway to save ELA: go here for info.

Here’s something I struggle with in my teaching and writing (blogging as well as papers). How do you keep your audience from mistaking specific examples for general principles, and vice-versa?

For instance (to pick a specific example!), “density dependence” is a general principle. It just means that per-capita growth rate varies with density (in any fashion, for any reason). The logistic equation is the first specific example of density dependence taught to undergrads, because it’s the simplest example. Which causes many students to answer exam questions as if they think logistic growth is one and the same thing as density dependence.

The obvious way to deal with this is to use multiple examples of the general principle. Which I try to do, of course. But just using, say, two examples rather than one doesn’t magically allow your audience to extract the general principle and distinguish it from example-specific details. If your two chosen examples share other features besides being two examples of the same general principle, your audience may well latch onto those other features as being somehow crucial. I have had this happen in my teaching, using multiple examples of density dependent models with carrying capacity parameters, thereby giving some students the mistaken impression (despite my best efforts to prevent this) that “density dependence equals carrying capacity”. But if your two chosen examples are as different as you can make them, your audience may have trouble seeing that they have anything in common at all. And if you try to get around these problems by using more than two examples, well, how many examples can you possibly provide, given that you only have so much time, or so many words, to work with?

As I said, this problem doesn’t just crop up when teaching undergrads; it’s not a problem specific to that audience. For instance, consider the “storage effect“, a very general type of coexistence mechanism. A colleague of mine has been arguing to me, correctly I think, that Peter Chesson and others interested in the “storage effect” haven’t always explained it in the best way. Part of the problem may be their reliance on an overly-limited range of examples. Briefly, the storage effect is a coexistence mechanism that can operate when environmental conditions and species’ densities fluctuate over time, in such a way that the strength of competition a given species experiences covaries in an appropriate way with environmental conditions. One way for the appropriate covariances to arise is if the competing species have stage-structured life histories with a long-lived, difficult-to-kill life history stage.* The examples that always get used include annual plants with seed banks, zooplankton with resting eggs, or coral reef fish and tropical trees with long-lived adults. It’s completely understandable why such examples are emphasized. The example of coral reef fish is what originally inspired Chesson and Warner (1981) to come up with the “lottery model” of coexistence, with Peter Chesson later generalizing the “lottery” mechanism to the storage effect. The storage effect is easy to demonstrate and illustrate using the sorts of mathematical models appropriate to species with such life histories.  Such life histories are common in nature, and all the best empirical examples of the storage effect involve species with such life histories. Such life histories even give the storage effect its name. When species with such life histories coexist via the storage effect, one can view each species as increasing when environmental conditions favor it, and then “storing” the gains in a long-lived, hard-to-kill life history stage, preventing it from being driven extinct even if conditions mostly disfavor it.

All of which has given many people the impression that those sorts of stage-structured life histories are essential to the storage effect. Which they’re not. The only life history feature you need is overlapping generations (Ellner and Hairston Jr. 1994). So even organisms that just reproduce and die continuously, with no stage structure at all, can exhibit a storage effect, as illustrated by the “flip-flop competition” model of Klausmeier (2010).**

Sometimes you can avoid the problem of confusing specific examples and general principles by avoiding general principles entirely. That is, if there’s a specific example or application of a general principle which is familiar to your audience, you can sometimes explain a new example or application by reference to the familiar example rather than to the general principle. I do this when I’m explaining the application of the Price equation to ecology (e.g., Fox 2010 Oikos, Fox and Kerr 2012 Oikos). The Price equation is an extremely general and abstract mathematical formalism with very broad applicability. But my audience is very familiar with one specific application: evolution by natural selection. That is, my audience is familiar with evolution by natural selection, even though they (mostly) don’t have any previous familiarity with the Price equation, or with the notion that evolution by natural selection is merely one specific example of the more general principle of “selection” (Price 1995). So rather than trying to explain the general, abstract principles and how they apply to whatever specific bit of ecology I’m talking about, I start by making an analogy between evolution by natural selection and the specific bit of ecology I’m talking about. I pitch what I’m doing not as applying an abstract, general principle in a specific ecological context, but as taking an idea that (as far as most of my audience knows) is specific to evolution, and transferring that familiar “evolutionary” insight to ecology. But if your goal is to convey the general principle, you obviously can’t get away with just talking about examples, because it wouldn’t be clear what they’re examples of?

Any ideas on how to deal with this problem? Does the order in which you introduce general principles and specific examples matter? (I feel like it doesn’t, or shouldn’t, but I’m not sure) There must be papers on this in educational psychology, but I don’t know that literature at all…

*You also need other ingredients. For instance, species can’t all respond in exactly the same way to environmental fluctuations.

**Klausmeier (2010) doesn’t actually say that the storage effect is what generates coexistence in this model, but Chris Klausmeier and I have figured out that that’s what’s going on. See this old post for some discussion. I didn’t walk through the details then and I’m not going to now, because I doubt most readers would be interested. But trust us, it’s a storage effect.

I’ve just been asked to review a paper by a leading journal, on a topic that I’ve never published on, but have blogged about.

Who says blogging has no real-world impact? 😉

The Canadian federal government is going to cease funding the Experimental Lakes Area. Since the late 1960s, the ELA and its 58 small lakes have been doing amazing long-term monitoring and experiments on whole lakes, including groundbreaking studies of eutrophication and acid rain. Closer to home, they have arguably the best long-term phytoplankton and zooplankton time series data in the world–very frequent sampling of many lakes, going back decades, all resolved to species level, and with consistent sampling procedures and the same taxonomists doing the identifications. I’m the lead organizer of one of the many collaborative groups to have used the ELA data.

The Feds want to transfer ownership of the facilities to a university or the provincial government, on the grounds that universities, not governments, should be doing this kind of science. As if universities and the provincial government have lots of spare money lying around to run the ELA. And as if governments don’t need the kind of science the ELA has always provided (many of their experiments have been chosen precisely for their direct policy relevance).

Most days I’m proud to call Canada home. Not today.

UPDATE: See here for a very good explanation of why this was a bad decision, which also places the decision in the context of the Canadian government’s other reductions in support for basic science (which in turn are part of the current government’s strategy of reducing all federal expenditures and revenues)

One of my pet themes on the Oikos blog is how subtle scientific errors can arise from using ordinary words to describe technical concepts (e.g., see here, here [especially the comments], and the last item on this list). Here’s a lovely passage on this, from physicist N. David Mermin. The context is a discussion of how difficult it is to teach relativity, not just because it conflicts with our intuitions about time and space, but because those intuitions are built into the grammar of our language:

Language evolved under an implicit set of assumptions about the nature of time that was beautifully and explicitly articulated by Newton: “Absolute, true, and mathematical time, of itself, and from its own nature, flows equably without relation to anything external… ” Lovely as it sounds, this is complete nonsense. Because, however, the Newtonian view of time is implicit in everyday language where it can corrupt apparently atemporal statements, to deal with relativity one must either critically reexamine ordinary language, or abandon it altogether.

Physicists traditionally take the latter course, replacing talk about space and time by a mathematical formalism that gets it right by producing a state of compact nonverbal comprehension. Good physicists figure out how to modify everyday language to bring it into correspondence with that abstract structure. The rest of them never take that important step and, I would argue that like the professor I substituted for in 1964, they never really do understand what they are talking about.

The most fascinating part of writing relativity is searching for ways to go directly to the necessary modifications of ordinary language, without passing through the intermediate nonverbal mathematical structure. This is essential if you want to have any hope of explaining relativity to nonspecialists. And my own view, not shared by all my colleagues, is that it’s essential if you want to understand the subject yourself.

Go here to read the whole thing. It’s wonderful.

It isn’t just in physics where our ordinary language and everyday experience get in the way of our understanding of the non-everyday. The same thing happens in economics (see, e.g., much of Paul Krugman’s writing, such as this). The same thing happens in evolutionary biology (famously, Darwin’s use of the word “selection” was widely misunderstood as attributing willful agency and goals to nature). And the same thing happens in ecology. I just wish I could articulate it as well as Mermin! Like an ugly duckling who hopes to grow into a swan, I dream of growing out of my natural snark-and-zombie-joke-based writing style into something like the above.

In particular, I’m still searching for a way of explaining the effects of disturbance by modifying ordinary language, without obliging readers (and my undergraduate students) to pass through the intermediate step of understanding math. But as I indicated by my recent post on another topic, I vacillate on whether that’s even possible, or whether the problem is just that I haven’t found the right words.

HT Robin Synder, a wonderful scientist and a better friend. And a FOOB.

My collaborator Dave Vasseur is seeking a postdoc for an NSF-funded project combining theoretical and experimental work on environmental variability and community dynamics. Details here. Dave is a super-smart and super-nice (and super-tall) guy, so this is a super-awesome opportunity.

 

p.s. to the previous post: Commenter Christopher Eliot (indirectly) makes the important point that all those stability concepts related to equilibria and other attractors assume that whatever system you’re studying can be described by a model with unchanging structure and parameter values. It’s only species’ densities (or whatever your “state variables” of interest are) that are allowed to change over time. Of course, in nature it’s probably hardly ever the case that a perturbation just changes species densities, while having no effect on any other aspect of the ecology of the system (e.g., the species’ behaviors, levels of key abiotic factors, etc.).

So maybe we need some new stability concepts! 😉 Just kidding. There are of course theoretical models which allow one or more key parameters to vary over time, often due to extrinsic variation in the environment (that’s sometimes called “external forcing”). And there are models which allow intrinsically-generated temporal variation in parameter values as well, which effectively just makes those parameters into additional state variables (e.g., models of eco-evolutionary dynamics, which allow some parameters to evolve via natural selection). So I don’t think we actually need any new stability concepts. But we probably do need a lot more work on models in which parameter values and even model “structures” can change over time. That’s really difficult and messy of course, which is why many theoreticians understandably hesitate to do those kinds of models.

The comments on a previous post indicated some understandable confusion on the part of some commenters as to the relationship (or lack thereof!) between various measures of “stability” in ecology. The term “stability” is infamous for meaning different things to different people, so that entire areas of the literature, particularly on the links between “diversity” and “stability”, are rife with confusion. Previous attempts to clear up the confusion (e.g., Pimm 1984) seem not to have had much long-term effect, so odds are that no blog post of mine is going to help much. But long odds of doing any good have never stopped me from posting before. 😉

Below is a list of every “stability” concept that I could think of off the top of my head last night, with a brief definition, a useful reference or two (sometimes to the paper defining the concept, sometimes just to an arbitrarily-chosen paper illustrating or applying the concept), and perhaps a few brief interpretive remarks.*

The single most important message you should take away from this list is that these different kinds of stability are different, and in many cases have little or nothing to do with one another. Even when they are related, it’s often in complex, non-intuitive ways. For instance, to pick just one possible example of many, the same conditions that synchronize the fluctuations of the abundances of different species (thereby increasing the temporal variability or “instability” of their total biomass) also can cause their fluctuations to decrease in amplitude and be bounded further from zero, both of which are “stabilizing” (Vasseur and Fox 2007). So the correct answer to the question “Do synchronizing factors decrease or increase stability?” is “What exactly do you mean by ‘stability’?”

I’ve grouped the different stability concepts into three rough categories, although the last category is a catch-all for stability concepts that don’t really fit with anything else.

I have not made any comments on the underlying drivers or causes of any of these stability measures. This post is just about clarifying concepts. Oikos is not paying me nearly enough** to try to write a post summarizing everything that’s ever been written on the drivers of all these different things!

You can talk about the stability of anything that can change over time, but for concreteness I’ll present definitions couched in terms of community ecology.

Cranky note to readers who are not mathematically inclined: This list is only an entry point into the literature. It is no substitute for reading and understanding the literature. In most cases this will oblige you to learn some math. I know that’s probably not what you want to hear, but that’s the way it is. Many important concepts of “stability” are mathematical. It is not possible for me, or anyone, to properly explain these concepts using only words. Math is more precise than words, so translating math into words always represents a loss of information and an increase in ambiguity. Words have multiple meanings, and “stability” is no exception. If you don’t know what meaning is being used in a particular context, there are going to be tears before bedtime. And while some theoreticians sometimes could do a better job of explaining themselves, there’s a limit to how much it’s possible for them to walk you through this stuff. Theoretical papers in the primary literature necessarily assume some mathematical expertise on the part of the reader, just like a paper reporting field experiments necessarily assumes some expertise on the part of the reader with things like experimental design and statistics. So if you want to understand this stuff well enough to work on it or teach it well, you’re going to need to put the effort in to learn some math.

So if you’re the kind of person who reads theoretical papers by skipping the equations and just reading the words, because you just want to “get the gist”, I’m sorry, but it’s pretty much inevitable that you’re going to end up confused about stability. When it comes to “stability” (and many other important ecological concepts), there either is no ‘gist’ to get, or the only way to get it is to first get the technical details. You’d be appalled, and rightly so, if some theoretician said to you, “Plants and algae are basically the same, they’re all green, the differences are just unimportant technical details that only plant ecologists need to worry about”. Which is exactly how big a mistake you’re making if you think that “All these different kinds of stability are basically the same, they’re all related, the differences are just unimportant technical details that only theoreticians need to worry about”. Yes, I know Charles Elton (1958) conflated several different stability concepts in his very influential book on invasion ecology. But he had the very good excuse of writing many decades ago. You don’t have that excuse, and shouldn’t follow his example.

And if you say, “But I don’t know enough math to really understand the details of different stability concepts,” then your choices are to learn some math, or work on something else. Just like how, if you don’t know enough about plants to really understand the plant ecology literature, your choices are to either learn more about plants, or work on something else.

And you know what? It can actually be fun to learn this stuff! Seriously. It’s like anything that takes a bit of effort to appreciate—once you get into it a little, it’s pretty cool.

Note to mathematically-inclined readers: Yes, many of my definitions are very imprecise. Please don’t hassle me in the comments. I am aware of more precise definitions. I chose to write the post in this way because it’s only an entry point into, and rough road map of, the literature, aimed at non-mathematicians. My imprecision will do no harm. No one is going to rely solely on my definitions. I’m only trying to be precise enough to give non-mathematical readers a sense of just how many different stability concepts there are, and just how different they are from one another.

Stability concepts related to equilibria and other attractors

These are the stability concepts that tend to get used most often by theoreticians.

Feasibility of equilibrium, and interior vs. boundary equilibria. Is there a set of non-zero densities at which all species have zero population growth rates? If so, the system has a feasible “interior” equilibrium. An equilibrium at which one or more species have zero density is known as a “boundary” equilibrium. An equilibrium at which one or more species have negative densities is “infeasible”, because negative densities are physically impossible.

Stability of equilibrium. Will species’ densities approach a given equilibrium over time if they’re not currently at that equilibrium (for instance, because they’ve just been perturbed away from their equilibrium values)? Equilibria that are stable in this sense are sometimes called “resilient”. The opposite is an unstable equilibrum, an equilibrium state that the community tends to move away from, rather than towards. A neutrally stable equilibrium is one the community tends to move neither towards nor away from.

(Asymptotic) rate of return to equilibrium. How fast does the community return towards, or move away from, an equilibrium state? Typically, theoreticians ask about the asymptotic rate of return, meaning how fast the system returns once it is already sufficiently close to equilibrium (systems that are sufficiently close to a stable equilibrium approach that equilibrium at a constant rate). This is an asymptotic rate because, in general, if a community is far from a stable equilibrium its rate of return to that equilibrium can fluctuate greatly over time, and can even be temporarily negative (see “reactivity”). But eventually (“asymptotically”) the system gets close enough to equilibrium to approach it at a constant rate.

Local vs. global stability of equilibrium. A community that returns to an equilibrium following a sufficiently-small perturbation (i.e. a perturbation that only changes species’ densities by a sufficiently small amount from their equilibrium values) is said to be locally stable. A community that returns to equilibrium following any possible perturbation that doesn’t actually eliminate a species is said to be globally stable.

Domain of attraction. How far can you can perturb species’ densities away from equilibrium and still have them return to that equilibrium? By definition, a globally stable community has the largest possible domain of attraction.

Alternate stable states. A community with multiple, locally-stable equilibria has alternate stable states. Which equilibrium the community approaches in the long run depends on its initial state. For instance, a community that starts out close to one equilibrium might approach that one rather than another, more distant equilibrium.

Attractor. Any state or sequence of states which a system tends to approach if it’s not currently in that state. Stable equilibria are one kind of attractor. Others include stable limit cycles and chaotic attractors. Most of the stability properties of equilibria are also properties of other kinds of attractors too. For instance,  attractors can be local or global attractors, a community can have alternate local attractors, etc. Also, some kinds of attractors are sometimes considered as more “stable” than other kinds (e.g., equilibria>limit cycles>chaos).

Permanence. A community is permanent if the community tends to move away from boundary equilibria. Basically, this means that, if one or more species are currently rare, they tend to increase rather than decline to extinction. Permanence implies the existence of some sort of interior attractor.

Reactivity. A system is reactive if, on being perturbed away from a stable equilibrium, it initially moves even further from that equilibrium before eventually returning.

Probability of local asymptotic stability (or feasibility, or permanence, or etc.). Given a specified model of system dynamics, with parameters randomly chosen from specified distributions, what is the probability that the resulting system will have a locally-stable interior equilibrium, or have a feasible interior equilibrium, or be permanent, or be reactive, or etc.?

Sign stability. An equilibrium which is guaranteed to be stable, just due to the signs of the interactions among the species (e.g., predators have a negative effect on prey growth rate, while prey have a positive effect on predator growth rate), no matter what the absolute magnitudes of those interactions.

References: May 1973 (stability of equilibrium, sign stability, probability of stability), Goh and Jennings 1976 (feasibility), Law and Morton 1996 (permanence), Neubert and Caswell 1997 (reactivity), Case 2000 (entry-level textbook covering various stability concepts related to equilibria and attractors)

Stability concepts related to variability

These are the stability concepts that, at least lately, are most often used in empirical studies, although there is a fair bit of theoretical work as well.

Temporal variability of a single variable. How much the abundance of a given species, or some other variable of interest, varies over time. Can be measured by various statistics, which themselves differ from one another (e.g., variance, coefficient of variation). Some authors use “constancy” to refer to the property of having low temporal variability.

Temporal variability of the sum of a set of variables. How much the total abundance or biomass of a set of species, or the sum total of some other set of variables, varies over time. The answer depends both on how the individual variables (the summands) vary, and on how they covary. All else being equal, negative covariation among the summands reduces the variability of their sum. Can be measured by various statistics, which themselves differ from one another (e.g., variance, coefficient of variation).

Range or amplitude of variation. The range of values over which the variable of interest fluctuates (maximum minus minimum). For variables that oscillate (cycle) in a periodic fashion, this is known as the amplitude of the oscillation.

Stationarity. A stationary variable is one that fluctuates over time, but with unchanging mean, variance, and other statistical moments. So for instance, a species that’s gradually declining towards extinction (i.e. mean abundance is declining) is not stationary.

References: Ives and Hughes 2002, Loreau and de Mazancourt 2008

Other stability concepts

Resistance. A system is resistant if it’s difficult to perturb it away from its current state. For instance, a small fire that kills grassland plants (thereby perturbing their abundances) might have no effect on tree abundances, indicating that trees are more resistant than grass to small fires.

Species deletion stability. If you remove a species from a community without changing anything else, does that lead, directly or indirectly, to any other species going extinct? If not, the system is species deletion stable. If so, then you have “secondary extinctions”, which could themselves lead to further extinctions (an “extinction cascade”).

Network topology stability. If you have a network of dependencies (e.g., predators are linked to, and depend on, their prey, and plants and pollinators are linked to, and depend on, each other), and you start removing species and/or links from that network, how many and/or which links do you have to remove in order to remove all the links on which a given species, or any species, depends? I made up the name for this, there doesn’t seem to be an agreed term in the literature.

Invasion resistance. If you add a new species to the community, at initially-low abundance, can it increase and establish itself? If not, the community is invasion resistant. Actually, this is related to local stability of boundary equilibria, so maybe it doesn’t belong in this subsection…Note that, in the theoretical literature, an “invader” is just an initially-rare species. It’s not, or not necessarily, “non-native” or “exotic”. In defining “invader” in the way that they do, theoreticians are focusing on the ecological determinants of invasion success. After all, species move around and establish new populations in new locations all the time, and they always have. Whether or not “non-native” (or “exotic” or “weedy” or etc.) species tend to have the properties that allow them to invade is a separate question; the mere fact that a species is “non-native” or “exotic” does not in and of itself affect its ability to invade.

Boundedness away from zero. How closely does the abundance of a given species, or some other variable that can only take on non-negative values, approach zero? The less closely it approaches zero, the more “stable” it is reckoned to be, on the basis that random events are more likely to cause the variable to actually go to zero if it closely approaches zero on its own.

Persistence time. How long does a species, or the community, persist before that species, or one or more of the species in the community, goes extinct?

References: Pimm 1980 (species deletion stability; an Oikos classic!), Case 1991 (invasion resistance), McCann et al. 1998 (boundedness away from zero)

*I wish I could just direct readers to Wikipedia for this, but the Wikipedia page on “ecological stability” is poor. The section on local vs. global stability says “Local stability indicates that a system is stable over small short-lived disturbances, while global stability indicates a system highly resistant to change in species composition and/or food web dynamics.” Huh? A locally stable system is one that’s…stable? Local stability has something to do with small disturbances, whereas global stability has to do with large disturbances resistance to change? Other sections are just as bad. I often find Wikipedia useful, but this isn’t one of those times. It’s not that the page is brief, it’s that what’s there is confusing or wrong.

**Indeed, they’re not paying me anything.

What are some of the biggest bandwagons in ecology right now? Why do some research topics turn into bandwagons, while others don’t? How do you tell a bandwagon from a non-bandwagon? Can a bandwagon be stopped? For the answers, check out this old post.

What if you want to crowdfund your science but are having trouble developing a professional-looking and compelling pitch? xkcd has the answer!

Many ecologists expect competing species to exhibit compensatory dynamics, meaning that the densities of any two competing species should be negatively correlated over time or across space. If your competitor increases in abundance, you ought to decline, right? After all, to the extent that two species are competing, that means that when one increases, it’s at the expense of the other, right?

Um, no. Or rather, not necessarily. For instance, environmental fluctuations can cause competing species to exhibit positive rather than negative correlations in abundance. Think of a drought which causes the density of every plant species to decline, even though they’re all competing. But there’s a deeper reason why you should not necessarily expect the densities of competing species to all be strongly negatively correlated with one another: in general, it’s mathematically impossible. I don’t think this fact is as well-known as it should be, so I thought I’d post on it.

Say you have just two competitors, each of whose densities you’ve measured at a bunch of different time points, or a bunch of different spatial locations. In this special case, the correlation coefficient (Pearson’s correlation or rank correlation) between the density of species 1 and the density of species 2 can indeed take on any value from +1 to -1. So depending on how strongly the species compete and other factors, it’s possible that their densities could be perfectly compensatory (correlation = -1). So for the sake of illustration, let’s assume that the correlation between their densities is -1.

Now imagine that there’s a third competitor. How will its densities correlate with those of species 1 and 2? Well, to answer that, you’d have to specify more information about the ecology of all three species. But without knowing anything about the ecology, I can tell you what the answer won’t be. Species 3 won’t have a correlation of -1 with both species 1 and 2. Because that’s mathematically impossible. For instance, if species 1 and 3 have a correlation of -1, then by definition species 2 and 3 must have a correlation of +1, i.e. perfectly synchronous rather than perfectly compensatory dynamics. Conversely, if species 3 has correlations of -1 with both species 1 and 2, then by definition species 1 and 2 must have a correlation of +1.

This three species case is a simple illustration of a general principle: the more species you have, the less-compensatory their dynamics can possibly be. It’s mathematically possible for any number of species to all be perfectly in sync with one another. But the more species you have, the less density compensation they can possibly exhibit, on average. In general, we can describe the pairwise correlations among s competitors with a correlation matrix, a square matrix with s rows and s columns, one row and column for each species. The number in row i of column j gives the correlation between species i and j, and of course the same number will appear in row j of column i since the correlation between species i and j is the same as that between j and i. The numbers on the diagonal will all be +1, since by definition any variable is perfectly correlated with itself. Now, as a matter of mathematical necessity, correlation matrices are positive semidefinite. Which turns out to imply that, the larger s is, the less-negative the off-diagonal elements of the correlation matrix can possibly be, on average.

For instance, in the special case when every pair of species has the same correlation, the minimum possible value of that correlation equals -1/(s-1). Here’s the graph for that special case:

As you can see, even with as few as 5 species, in this special case the minimum possible correlation is only -0.25, which is pretty weakly compensatory. In the limit, as s goes to infinity, the minimum possible correlation goes to 0 (i.e. species fluctuate independently of one another).

Of course, in reality the pairwise correlations won’t all be equal, and so even with many competing species it’s possible that some pair of them might have strongly compensatory dynamics. But if they do, that just implies that some other pair of them must have strongly synchronous dynamics. On average, the pairwise correlations can’t be more than slightly negative when you have more than a few species.

Note as well that the same basic point holds for other measures of synchrony. For instance, the exact same points hold if you want to analyze synchrony in the frequency domain by looking at phase differences.

This mathematical fact is certainly familiar to folks who do a lot of work on this stuff, like my collaborator Dave Vasseur. But it deserves to be more widely known. Lots of ecologists have the vague sense that competitors ought to exhibit compensatory dynamics, and so are somewhat surprised to learn that compensatory dynamics are actually quite rare in nature.  But the reason they’re rare is mathematical, not ecological.  Which means you cannot use the rarity of compensatory dynamics as evidence for anything about ecology. For instance, you can’t say “These species only exhibit weakly compensatory dynamics, so they must not be competing very strongly”. You can’t even say “These species only exhibit weakly compensatory dynamics, so environmental fluctuations must be generating synchrony that overrides the strongly compensatory dynamics that would otherwise occur.”

Just to be clear, there absolutely is scope for the strength of synchrony or compensation to vary among communities, and among different pairs of species, for all kinds of interesting ecological reasons. But if you aren’t clear on what dynamics are possible, you’re liable to misinterpret actual dynamics.

In a previous post I expressed a bit of wariness that crowdfunded science, by requiring new forms of salesmanship on the part of scientists, might tend to favor style over substance.

But if the style is going to be this funny, I’m all for it! Zen Faulkes’ SciFund project is about the environmental and evolutionary drivers of gigantism in sand crabs. “Gigantism” is relative, of course–which Zen has illustrated with a great picture of a “giant” sand crab trying to beat the c**p out of his fingertip. The picture’s hosted on a meme generator site that lets you add your own caption, which a bunch of people have already done, and the results are hilarious. Go check it out!

Readers are encouraged to post their own pictures to the meme generator site and let us know in the comments.

(Beware that the site can be slow, which caused me to accidentally post a caption three times…)

UPDATE: Here are some samples: