Blogging ESA: Species Traits and Community Assembly

By Jacquelyn Gill on August 8, 2012 • ( 5 Comments )

I’ve been mostly attending talks on community assembly and trait-based ecology so far, as both are subjects I don’t know much about but am interested in. I think there are some really neat opportunities to apply a paleo-perspective to both fields, and I’ve been kicking around potential project ideas for my postdoc and beyond.

I started the Tuesday off with a talk by Jeanine Cavender-Bares, on the evolution of traits that drive community assembly. Not all combinations of traits are possible; in the extreme regions of the niche axis, you run up against constraints by either physiology (i.e., there’s a physiological limit to how quickly a plant can produce leaves) or natural selection. Cavender-Bares showed several examples indicating that functional traits and niche axes are rarely more conserved than expected, indicating a weak signature of phyologeny in predicting ecological divergence of taxa, but that there is an evolutionary footprint of shared ancestry nonetheless. One example was the evolution of response in plant traits to fire regimes. A modern experiment at Cedar Creek indicated that the traits that drove community assembly in savannas under changing fire regimes arose from 140-80 million years ago, during the Cretaceous (though I wondered a bit about how this jives with the much later timing of the evolution of grasslands during the Miocene).

Justin Wright‘s talk on introspective trait variability was quite interesting but very sobering. Disturbance, position along an environmental gradient, or species turnover can all result in a range of intraspecific variability in measured trait values. Traits vary so much with (some) species under different conditions conditions that I wonder whether it’s possible to measure the relative abundance of traits in the paleorecord, when environmentally conditions were highly variable through time. One idea: it would be really cool to try growing plants under the environmental conditions of the last glacial maximum, measure a set of traits, and compare those values with plants grown under modern conditions to get a sense of the range of variability during the Quaternary. One big take-home message of the meeting (for me) is that we should really be thinking about trait distributions, as opposed to trait means. Also, organism plasticity in traits not only introduces noise, which needs to be taken into account, but is in itself a trait that needs to be studied further. It is possible to partition how trait variance is structured, to get a sense of what’s contributing to the noise, which I’d like learn more about.

As a closing thought: Is it really useful to think of a species as a “bundle of traits,” or will we find that species are more than the sum of their parts?

There’s a nice little post on traits over at the Oikos blog by Jeremy Fox.