Posted by: oikosasa | January 17, 2014

Per Brink Award 2014

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.

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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.”

OIK_1298_fu1The 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.

Posted by: oikosasa | January 15, 2014

Invasive mussels as ecosystem engineers

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).

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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.

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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).

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

Posted by: oikosasa | January 13, 2014

On the importance of fruit in primate diets

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.

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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?

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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:

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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.

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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

Posted by: oikosasa | January 2, 2014

Monsterciliates as pac-man predators

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.

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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).

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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.

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As it turns out, it can.

Posted by: oikosasa | December 30, 2013

Frugivore bird response to habitat loss and plant invasions

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.

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.

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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 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.

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.

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.

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

Posted by: oikosasa | December 20, 2013

Top-cited Oikospaper

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?

Jeff in TanzaniaThe 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:

 

Posted by: oikosasa | December 17, 2013

Hurray! We have a new cover!

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!

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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.

Posted by: oikosasa | December 13, 2013

Joint effects of predator and parasite on prey stress levels

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.

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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

Posted by: oikosasa | December 3, 2013

Editor’s Choice December

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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.

Posted by: oikosasa | November 29, 2013

No more calls for the end of invasion biology?

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.

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.

Posted by: oikosasa | November 26, 2013

The importance of territorial behavior in ecological networks

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.

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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.

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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).

Posted by: cjlortie | November 23, 2013

Chasing the white rabbit: novelty as a filter for editors

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.

400px-Down_the_Rabbit_Hole

Posted by: oikosasa | November 22, 2013

The typical ecological answer – it depends

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. 

spartina_salt_marsh

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.

fiddlers_in_marsh

 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. 

fiddler_close-up

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

Posted by: oikosasa | November 20, 2013

New Preprint server

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?

Posted by: oikosasa | November 15, 2013

New aspects of land use impacts on biodiversity

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.

R_Lewis_Blog_Image

Posted by: cjlortie | November 12, 2013

Upping your theory game by Samuel M. Scheiner

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.

Posted by: oikosasa | November 12, 2013

Editor’s choice November 3.0

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!

Table1_399b

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.

Figure1_399b

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)]

Posted by: oikosasa | November 8, 2013

Reminder: Photo competition- Oikos cover 2014

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:

borer-etal-oikos-concept-fig

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.

sedg-oblique-20030326-small

Posted by: cjlortie | October 29, 2013

Editor’s Choice November: Indirect interactions

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):

Bathyporeiapilosaweb

 

Sample petri dish arenas in general:

mold2

Posted by: cjlortie | October 29, 2013

Editor’s choice November: Dispersal and climate change.

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.

OLYMPUS DIGITAL CAMERA

Posted by: oikosasa | October 28, 2013

Measuring the strength of trade-offs

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.

Mountain goat sucklingroe deer ecographie

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.

Posted by: oikosasa | October 25, 2013

Can plants make a decision?

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.

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.

Posted by: oikosasa | October 22, 2013

Safer with close neighbors

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:

IMG_0421Many 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. 

IMG_0610

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.”

IMG_2094-2029

Posted by: oikosasa | October 18, 2013

Crowding effects on indfidelity

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.

McKellar

Posted by: oikosasa | October 15, 2013

Like a missile attack on the ecosystem

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

Buoy_PeterLake_2012-07-12

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.

Posted by: oikosasa | October 11, 2013

Where am I and Why?

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.

Kubisch

Posted by: oikosasa | October 8, 2013

Multi-scale co-ocurrence patterns in India

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:

SelasMoon

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.

SelasHare

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.

VidarSelas3

Posted by: oikosasa | October 1, 2013

Temperature variability and population dynamics

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

Posted by: oikosasa | September 24, 2013

Ecological periodic tables

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

OIK_717_f1

Posted by: oikosasa | September 20, 2013

Mind your “girth”!

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.

Posted by: oikosasa | September 13, 2013

Dispersal at the heart of our thinking

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!

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!

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!

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).

 

Posted by: oikosasa | September 10, 2013

The higher up, the smaller the seeds

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).

Posted by: oikosasa | September 6, 2013

Editor’s choice September

DriesFor 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

Posted by: oikosasa | August 29, 2013

Editor’s Choice August

DriesLook 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.

Posted by: oikosasa | August 20, 2013

Parasite changes during an epidemic

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

Posted by: chrislortie | August 15, 2013

Intecol 2013 presentations

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

ant-3-xxl

Posted by: oikosasa | August 14, 2013

Lessons from Late Jurassic

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.

380_1

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. 

380_2

Exploring the Jurassic seafloor as it is exposed, in the Kimmeridge Clay Formation, today on the foreshore.

380_3

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.”

Posted by: oikosasa | August 13, 2013

Meet our EiC in London next week!

 

 

announcement

Posted by: oikosasa | August 2, 2013

Moving plants and invasions

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.

Buckley1

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.

Buckley2

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.

Buckley3

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.

Posted by: oikosasa | July 29, 2013

Swans go with the flow

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

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 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

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

Posted by: oikosasa | July 26, 2013

Personality and metabolic rate

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.

Wytham Woods mistnetted great tit personality assay room

Posted by: oikosasa | July 22, 2013

Mom knows best – maternal care in perennial plants

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.

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.

Posted by: oikosasa | July 19, 2013

Scared of darkness?

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

community

Posted by: oikosasa | July 16, 2013

Welcome Isabel Smallegange – new SE

OLYMPUS DIGITAL CAMERAWelcome 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.

male morphs mites more mites copy

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.

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