Functional trait distributions, phylogenetic structure, and the assembly of a Neotropical tree community in Amazonian Ecuador

Recently developed functional trait- and phylogenetic-based analyses provide a powerful framework for inferring community assembly process, particularly in instances when manipulative ecological experimentation is impractical. We applied these methods to a highly diverse tropical tree community in 25 ha. of the Yasuni Forest Dynamics Plot (FDP) in Amazonian Ecuador in order to determine how the importance of key ecological assembly processes, including niche differentiation, habitat filtering, and neutral assembly, change in importance with spatial scale. We coupled null models and spatial distribution data with recently compiled or collected data on the seeds, wood and leaves of species present in the FDP. In particular, we have collected leaf functional trait data for over 550 of the 1000+ species present in Yasuni. While further trait collection is needed for a full analysis, preliminary analysis of 10 20x20m quadrats within the FDP reveal trait distribution patterns that suggest a role for niche differentiation (limiting similarity) and habitat filtering. Preliminary phylogenetic community analyses indicate that co-occurring species in 20x20m quadrats are more closely related than expected (phylogenetically clustered), a pattern consistent with habitat filtering. Phylogenetic analyses did not reveal patterns consistent with niche differentiation (limiting similarity), however this may be due to the low power of phylogenetic methods to detect patterns due limiting similarity in large communities, as demonstrated in recently published simulations (Kraft et al. in press). Our results indicate that despite relatively homogeneous appearances, lowland tropical tree communities may be structured by ecological processes that act on ecophysiological differences between co-occurring species.