Untangling the positive association of phylogenetic, functional, and taxonomic diversity with alien bird species richness

Abstract

Understanding the ecological mechanisms behind biological invasions remains a major focus of conservation biology and ecosystem management. Several hypotheses highlight that different facets of native biodiversity affect the establishment and spread of alien species. Here, we approach this question by examining the spatiotemporal relationship between alien bird species richness and different facets of biodiversity (taxonomic, functional, and phylogenetic) using breeding bird atlases for three U.S. states and for two time periods in each state. We associated native species richness, and functional and phylogenetic diversity with alien species richness, using generalized least squares models. Our results show that, consistently, across the three states and two time periods examined, alien species richness is positively associated with native diversity, and particularly with phylogenetic diversity. The relative importance of biodiversity metrics reflecting the functional or phylogenetic range occupied by the assemblage seems to advocate in favor of the importance of resource diversity as a main driver of both native and alien diversity. The secondary importance of biodiversity facets reflecting species functional or phylogenetic similarity, along with the lack of importance of functional or phylogenetic clustering or overdispersion, implies that if this relationship is shaped by biotic interactions, then biotic interactions facilitating coexistence (including even processes like predator-mediated coexistence) are far more important than adversarial interactions like competition, at least at the scale of our analysis. Finally, the dominance of phylogenetic metrics over functional ones highlights the adaptive potential of a community accumulated over long lineage history may play an additional role as a source of information on evolutionary processes driving diversity patterns.