| Summary: | Understanding mechanisms underlying distribution of biodiversity remains a central issue in ecology. I integrate ecological and phylogenetic information at multiple spatial scales to better understand neotropical primate distribution and community structure. I investigate the variation within species ranges in relation to species richness and patterns of species relatedness. Results suggest positive associations among species throughout their distributions, whereby species tend to present higher richness within their ranges than average richness for the entire taxon. However, comparing empirical distributions to a null model of range cohesion suggests mechanisms other than dispersal are setting a limit to the number of species capable of co-occurring throughout a species range. These differences in species associations across geographic ranges generate variation in local community composition. I analyzed the relative contribution of ecological, historical and spatial processes in determining taxonomic and phylogenetic community structure across 74 sites throughout the Neotropics. Spatial predictors explained most of the independent variation for taxonomic and phylogenetic metrics, suggesting spatial processes, such as dispersal limitation, are important determinants of community structure. Most of the contribution of environmental predictors was associated with spatial processes, evincing importance of environmental and spatial gradients in determining change in community structure. While the overall contributions of predictors were similar for taxonomic and phylogenetic metrics, analyses of phylogenetic metrics independently presented complex relationships. At local communities, niche differentiation is expected to allow species coexistence. However, these differences may reflect evolutionary constraints of species, rather than active selection. I investigated niche overlap and presence of niche conservatism for primate species at three communities. For the niche characteristics measured by my study, I found no significant differences in niches of closely related species within sites. However, when comparing niches across sites, significant differences were registered between populations of the same species or closely related species. These findings suggest ecological differentiation may be acting at large spatial scales promoting niche differentiation, while at local scales phylogenetic constraints may be a stronger driver of community structure. Overall, these results represent valuable insights regarding our understanding of mechanisms responsible for generating and maintaining community structure for a highly diverse tropical mammal radiation.
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