COS 257-1 - Community structure along environmental gradients

Abstract: Theories of community assembly often assume that community structure is static and independent of environmental variables. Moreover, the role of traits has played an under-appreciated role for explaining the relative abundance of species. Here, we develop a trait-based model for species subject to resource competition and predation, and derive an explicit expression for the trait-abundance distribution under certain assumptions. We also make theoretical predictions about macroecological patterns (evenness, mean biomass, etc.) in species and trait abundances as they relate to the joint effect of resource availability and predation. To test our predictions, we use phytoplankton community data from 14 alpine lakes in western Europe to demonstrate that communities are mainly structured by resource allocation towards the most abundant species. In accordance with our predictions, we also find that increased temperatures shift species abundance distributions towards higher mean and total biomass. Our mechanistic framework for modeling species abundance patterns using traits offers a powerful new way to explain community structure.