Role of environmental, historical and spatial processes in the structure of Neotropical primate communities: Contrasting taxonomic and phylogenetic perspectives

Background/Question/Methods

A central goal in ecology is to understand observed patterns of biodiversity. Ecological (environmental filtering), historical (biogeographical filtering) and stochastic (dispersal limitation) processes have been proposed as key mechanisms structuring communities. However, these are not mutually exclusive, and local community composition may often reflect the interaction of these processes during the course of assembly. Recently, inclusion of phylogenetic information into studies of community structure has provided valuable insights into potential underlying mechanisms that have shaped composition and phylogenetic structure of communities. The present study simultaneously evaluates relative importance of ecological, historical and stochastic processes on taxonomic and phylogenetic structure of Neotropical primate communities.  Data on community composition for 74 sites was gathered from literature. Communities were characterized based on taxonomic and phylogenetic composition. Three predictive matrices were used as explanatory variables representing ecological (environmental), historical (riverine barriers and Pleistocene refugia) and dispersal-based spatial hypotheses (spatial PCNM vectors based on geographic coordinates). Variation partitioning analyses were used to decouple independent and shared effects. Permutation procedures based on redundancy analysis (RDA) were used to determine if explained variation was statistically significant.

Results/Conclusions

Forty-nine percent of variation in taxonomic structure and 66% of variation in phylogenetic structure was explained by selected predictor variables. Independent effects of spatial variables explained the largest portion of variation in both diversity metrics. Fractions representing shared effects of historical and spatial variables, and of all variables combined were also large and significant.  Independent effects of environmental and historical variables were small to non-existent  (< 4%). When analyzing each phylogenetic metric independently the relative contributions of shared fractions changed, although the independent spatial fraction remained the most important predictor. These results evidence that purely spatial processes, such as dispersal limitation, may play a stronger role in structuring primate communities than niche mechanisms and historical events. Furthermore, we find that influence of ecological and evolutionary mechanisms is conflated with spatial processes, suggesting community structure is determined jointly by spatial processes structuring environmental gradients and biogeographical processes. Although the relative contributions of each predictor variable was similar between taxonomic and phylogenetic metrics, a deeper examination of phylogenetic metrics suggests that ecological, historical and spatial mechanisms interact in complex ways to determine current patterns of phylogenetic community structure.