Posted by: Jeremy Fox | May 4, 2012

Cool new Oikos papers

Some forthcoming Oikos papers that caught my eye:

Tuomisto (in press) is a “consumer’s guide” to evenness indices, showing how they are mathematically related to one another, and to partitionings of diversity into alpha and beta components. The take home message is the same as in my recent post: different “evenness” indices actually measure different things. To pick one, you need to know exactly what you’re trying to measure. And it is not interesting to simply ask whether different indices give you different results, because they will as a matter of mathematical necessity.

Ackerman et al. (in press) use a comparative approach to test the popular and intuitively-appealing hypothesis that pollinator extinctions and temporal fluctuations in pollinator abundance select for flowers attractive to many pollinator species. By combining long-term census data on 37 species of Panamanian euglossine bees with data on bee and flower phenologies, Ackerman et al. show that the “risk hedging” hypothesis doesn’t work. There’s no tendency for generalized plants to be pollinated by more variable pollinators. Rather, the longer a plant flowers, the more bee species visit it, which suggests that plant-pollinator specificity is just a sampling phenomenon (the longer you flower, the larger the “sample size” you’re taking from the pollinator fauna). As a contrarian, I always like to see widespread intuitions put to the test–especially when they’re found wanting.

New et al. (in press) develop a stochastic, mechanistic predator-prey model for the dynamics of hen harriers and red grouse, fit it to long-term time series data using state space methods, and use the fitted model to evaluate alternative management strategies for predator suppression. Red grouse is a popular game species in the UK, but you can’t hunt grouse that hen harriers have killed. It’s illegal to cull harriers, leading to the idea of “diversionary feeding”–give the harriers alternative food so they stop hunting grouse. Which sounds like a good idea until you realize that (i) it’s expensive, and (ii) in the long run, you might just build up higher harrier abundances, which would lead to even heavier predation on grouse than would otherwise occur (a specific example of the general principle of apparent competition; Holt 1977). The results show that harriers do suppress both average grouse density and grouse cycle amplitude (red grouse are a famous example of cyclic dynamics, driven by density-dependent parasitism). That’s a really cool result in and of itself. There aren’t many good examples of “community context” mediating the stability of population cycles.  The results also show that diversionary feeding, as currently practiced, makes only a marginal difference at best.

Numerous other forthcoming papers caught my eye–we’ve got a lot of good stuff coming out. But I need to get back to marking, so they’ll have to wait for a future post.

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