Phylogenetic conservatism in the traits that drive community assembly

Background/Question/Methods

In the face of rapid changes in the Earth’s biota, understanding the evolutionary forces and ecological processes that shape the ecosystems upon which life depends has never been more pressing.  The conservatism of organismal structure and function over evolutionary time has long been recognized. Phylogenetic information is increasingly used as a proxy for functional trait information, with the assumption that the phylogenetic distance separating taxa is strong predictor of their ecological divergence. Yet we still have much to learn about the context and scale dependence of phylogenetic signals and constraints in traits. In this talk we critically examine different approaches for evaluating the evolutionary conservation of traits and show trends from a review of the literature of Blomberg's K for functional traits in relation to contrasting null models. We then examine, both in the literature and in a series of forest and vascular plant communities, the extent to which traits that are critical for driving community assembly across environmental gradient and spatial scales are phylogenetically “conserved”.

Results/Conclusions

We find across many studies and systems that functional traits and niche axes are rarely more conserved than expected under a model of Brownian motion.  Despite this apparently weak signature of phylogeny in predicting the ecological divergence of taxa, shared ancestry plays an important role in driving the structure of communities.  Our results highlight the possible shortcomings of studying (and defining) phylogenetic niche conservatism based on single, whole-tree metrics. At the same time, we provide compelling evidence for the ancient footprint of history on the ecological assembly and turnover of species.