Phylogenetic and phenotypic filtering in hummingbirds from urban environments in Central Mexico

Abstract

Cities act as biological filters on native biodiversity, selecting for traits allowing species to use urban resources, which may modify the phylogenetic structure and composition of biotic assemblages. Although many studies about urban filtering have included bird communities, few have focused on diverse and specialized groups, such as hummingbirds. Here, we investigate if: (1) the urbanization process may have modified the phylogenetic and phenotypic structure of regional hummingbird assemblages in five cities along the Trans-Mexican Volcanic Belt in central Mexico, and (2) hummingbird species in urban environments have been filtered through the selection of particular morphological traits. We measured eight morphological traits related to the ability of hummingbird species to use resources, three of which (wing chord, culmen and bill curvature) were retained for phenotypic analyses. We estimated phylogenetic (MPD, mean pairwise distance, and MNTD, mean nearest taxon distance) and phenotypic structure values (pMPD and pMNTD) in regional and urban hummingbird assemblages, which allowed us to assess significant phylogenetic structure and phenotypic similarity among coexisting species, respectively. We also calculated phylogenetic signal to determine if traits are labile or conserved. We performed generalized linear mixed-effect models and a classification and regression tree analysis to determine which traits explained species’ presence in urban environments. Our results showed that urbanization modified the phylogenetic structure from a random pattern in regional assemblages towards more overdispersed values in urban assemblages, while phenotypic structure values changed either towards clustering or overdispersion in the different cities. Regression tree analyses showed that traits related to body-size and bill culmen may influence the presence of different hummingbird species in cities. Our results show that the urbanization process may change the phylogenetic and phenotypic structure of hummingbird assemblages, favoring species with generalist morphologies (intermediate body-sizes and relatively longer bills).