Untangling the influence of ecological and evolutionary factors on trait variation across hummingbird assemblages

Phylogenetic community ecology combines phylogenetic hypotheses with local species composition and functional-trait information to evaluate historical and contemporary mechanisms influencing local assemblage structure. Most studies assume that, if functional traits are conserved, then patterns of trait variation should match patterns of phylogenetic structure within local assemblages. Here we evaluated if we could predict trait structure by assuming that environmental filtering or biotic interactions work primarily on phylogenetically conserved functional traits. We investigated patterns of phylogenetic assemblage structure and functional-trait variation in bill length, wing length, and body mass in 236 hummingbird assemblages (126 species) across two major gradients in northern South America: elevation and precipitation. While mean trait values for assemblages vary predictably based on empirical knowledge of hummingbird biology, the distribution of trait values within assemblages do not correspond to those predicted based on phylogenetic signal and phylogenetic structure. Instead, we were able to identify instances where assemblages have high levels of morphological variation despite their close evolutionary relatedness and vice versa. Our results provide support for both filtering and biotic interactions across gradients, as has been documented in other studies.