Functional trait and phylogenetic-based tests of community assembly in a Neotropical forest

There is debate about the role of species-level differences in ecological strategy in promoting coexistence in diverse communities, particularly in tropical forests. One challenge in resolving this debate is that it is often difficult to perform manipulative experiments in tropical forests due to the large size and long lives of many tree species. Recently developed methods based on the functional similarity and the phylogenetic relatedness of co-occurring species offer an alternative approach.;I collected and complied functional trait and phylogenetic information on over 1,100 tree species found within the Yasuni forest dynamics plot, a 25 hectare plot of Amazonian forest in Ecuador where all trees are identified and mapped. Using a null model approach, I found that co-occurring trees at Yasuni tend to be more functionally distinct from each other than expected, in a manner consistent with a role of habitat associations and niche differentiation.;Phylogenetic tests of community structure offered similar conclusions to trait-based tests, though they did not present as complete of a picture. Simulation models of community assembly under distinct ecological processes were used to assess the statistical power of trait and phylogenetic methods under a variety of conditions. The size of the community, the phylogenetic scope of the analysis, and the type ecological process being tested for all influenced the statistical power of trait and phylogenetic methods to detect nonrandom patterns.;I explored the spatial scale at which different ecological processes were detectable at Yasuni. Habitat associations were detectable from small to intermediate spatial scales within the forest, while niche differentiation was only detected at smaller spatial scales, which may be due to a lack of statistical power at larger scales. Taken together, the results support a role for ecological strategy differentiation in promoting diversity in one of the most species-rich communities on the planet.