Thursday, August 9, 2012

ESA 2012: Day 4

 For some reason, Day 4 had many talks I wanted to see, just when the effects of late nights and over-caffeination were starting to peak. The reward to remaining awake through a day of talks was that I got to hear some excellent ecology.

At 8:20 (yes, 8:20) in the Biodiversity III session, Xubing Liu spoke about some of the work his research group is producing to expand our understanding of the Janzen-Connell effect. (For a good example of this work, see The Janzen-Connell effect is a density-dependent mechanism in which proximity to individuals of the same species increases their chance of encountering species-specific predators or diseases, and therefore reduces their chance of survival. This is hypothesized to produce coexistence by maintaining lower abundances and higher diversity. In this talk, Liu explained how intraspecific variation could similarly be maintained via a Janzen-Connell effect. He showed experimentally that decreasing the degree of relationship between two individuals of the same species (increasing intraspecific diversity) increased their odds of surviving fungal infection. Such a mechanism could help explain how intraspecific variation is maintained, which is a hot topic these days.

A talk I found particularly interesting, perhaps because it was so different in content and style from my own work was that by Robert Beschta from Oregon State University. He convinced me, without statistics or plots, that the outcome of a natural experiment – the removal of apex predators from America’s park system – was highly detrimental to those ecosystems. Removal of wolves and cougars from National Parks such as Yellowstone and Olympia have produced many changes in community structure and function – the understory disappeared as deer and elk browsed all young greenery, river edges eroded without shrubbery, and forests aged. Yellowstone provided an additional validation to this conclusion; re-introducing wolves appears to be producing gradual reversion to more diverse and functional habitat.

Diane Srivastava further provided the type of perspective only gained from years of research. She also illustrated that the contribution of a body of work is often more than the sum of its parts. Diane has spent 15 years of studying a bromeliad system in which multiple invertebrates live in the water collected in the plants, forming a complex ecosystem with multiple trophic levels. The data collected over this time allowed her to perform a meta-analysis which shed more light on the dynamics of this system than any individual study allowed.

There were multiple talks from students of Peter Chesson, an eminent theoretician, and all shed light on mechanisms of coexistence. Although perhaps too complicated to explore in a short summary, they covered topics in keeping with other work from the lab, especially the role of temporal and spatial variability in driving fluctuations in recruitment and ultimately coexistence, and in understanding how mechanisms will scale with space. His students were well informed on the intricacies of Chessonian theory and the talks certainly created lots to think about.

Finally, two talks discussed the growing problem of reconciling trait- and phylogenetic-based community ecology. Rebecca Best presented the results of a amphipod competition experiment, in which she examined whether feeding traits or phylogenetic distances were a better explanation for the resulting diversity and abundances. She found, as is not uncommon, that traits were by far more useful in understanding the amphipod community. She didn’t stop there, however, and tested further how the phylogeny and trait values actually related – it turned out that traits and phylogeny were not correlated, and represented different mechanisms at play in the species' ecologies. Though she found that phylogenies could not predict the outcome of her community experiment, she concluded that this didn’t mean that phylogenies were not important, only that they were important at different scales or in different mechanisms then she had been focusing on.

Finally, a talk directly relevant to Best’s work came from the EEB & Flow’s Marc Cadotte. Since it was a well-received and interesting talk, I feel like giving his talk a plug here isn’t too biased. Cadotte presented a metric meant to incorporate both trait and phylogenetic information, and further to incorporate them in a meaningful way. Name FPDist (for functional phylogenetic distance), this metric incorporates an additional axis (functional diversity): this can be represented with a phylogenetic tree in which the x-axis represents trait distance and the y-axis phylogenetic distance. This allows you to visualize trait divergence and convergence in a way that traditional trees cannot. Further, the metric he presented is a function of both traits and phylogeny, combined in such a way that the relative importance of each can be captured and recognized. This allows us to more fully investigate both traits and phylogeny contribute to community diversity. No doubt an interesting paper will follow soon.

Off to survive one more night and one more morning.


Brady Allred said...

I've been enjoying yours and others' reports of the meeting. Thank you.

I wasn't there, but the comment of Beschta convincing "without statistics or plots" has the connotation of little data, experimental work, or testing. To believe in something without data is what most of the world calls faith or dogma.

See Winnie (in press) ( for a different view of the proposed mechanism, with data.

Caroline Tucker said...

Hi Brady - thanks for your comment. You are right - good science doesn't rely on expert opinion alone, although the proposed mechanism (top-down control) seemed plausible enough that I might not go so far as to call it dogma :) I probably overestimate how well people with a lifetime of experience and ecological training understand the mechanisms in their system (I refer to this as 'field ecology envy'). And indeed I think there is lots that we can learn from these kind of people. But I probably overstated how 'convinced' I was (i.e. I wouldn't go releasing wolves in parks based on this talk alone). Thanks so much for the link, it looks quite informative and data-full :-)

Rebecca Best said...

Hi Caroline - I just saw this, but thanks very much for the summary! I wish I'd had the chance to meet you at the meeting - Marc was telling us about your work. Part of the stuff I talked about at ESA came out today if you're interested:

Thanks again!

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