While environmental characteristics can determine niche availability, historical events influence the set of species that can potentially fill these niches. Given this possible interaction, jointly examining effects of ecological, historical and neutral processes of community assembly is a sensible step towards understanding patterns of biodiversity. Furthermore, incorporating aspects of diversity that account for species evolutionary histories may provide new dimensions to interpret mechanisms of community assembly. We simultaneously evaluated the relative importance of niche and historical processes structuring taxonomic and phylogenetic composition of Neotropical primate communities. Data on community composition for 74 sites was gathered from published literature. Each community was characterized in terms of species composition and phylogenetic structure. A presence-absence matrix was used to represent taxonomic structure. Five different metrics characterized phylogenetic diversity and structure. Three predictive matrices were used to explain variation in taxonomic and phylogenetic structure. Each of these matrices represents a different ecological or historical process: 1) environmental variables (temperature, precipitation, seasonality and productivity), 2) riverine barriers and 3) Pleistocene forest refugia. We used variation partitioning analyses to decouple independent and shared effects of these three hypotheses. Permutation procedures were used to determine whether variation explained by each hypothesis was greater than expected by chance.
Nearly 40% of variation in taxonomic and phylogenetic structure was explained by a combination of all predictor variables. Environmental variables by themselves accounted for the most variation in phylogenetic structure (10%). The shared component of environment and Pleistocene refugia accounted for an additional 5% of variation. In contrast, Pleistocene forest refugia independently explained the most variation in taxonomic structure (10%). Shared effects of riverine barriers and forest refugia explained an additional 10% of variation in taxonomic structure. The fraction representing shared effects of all predictors explained an additional 5% of variation for both diversity metrics. Contrary to initial expectations, environmental factors were more important predictors of phylogenetic structure, while historical factors were more important predictors of current community composition. Environmental effects on phylogenetic results may be related to previously reported potential for energy and productivity to enhance speciation rates, particularly in the Neotropics. Effects of historical variables on community composition might be the result of interspecific variation in species dispersal abilities during vicariant events taking place at times when different lineages diversified. These results demonstrate that analyzing different aspects of diversity gives us a better understanding of how multiple mechanisms of assembly interact to structure highly diverse communities.