Biogeographic and Ecologic Drivers of Avian Diversity

Evolution and diversification are inextricable intertwined with geography and ecology. The geographic landscape in which a taxon evolves can limit the environments in which it is found or provide opportunities for repeated range contraction and expansion through climate fluctuations. The presence (or absence) of regions with varying levels of climatic stability and the presence (or absence) of major biogeographic boundaries can shape the way in which species diversify or locally go extinct. In tandem with these geographic processes are ecological processes: taxa may interact with co-occurring taxa in the community, and can be limited by biotic barriers (such as disease) or develop specific biotic niches (such as commensalism). In this dissertation, I analyze biogeographic and ecologic drivers of avian evolution from the continental level to individual species interactions. I frame these issues hierarchically, starting with two chapters on large, broad scale patterns that affect not only birds but also mammals, and gradually focusing more and more finely on factors affecting avian systems. The latter part of the dissertation includes three 'case studies' of biogeographic dynamics, with one chapter on community-level dynamics, one on single-lineage diversification dynamics, and one on biogeographic dynamics within lineages that are 'locked' into a mimicry dynamic. Through this research, I demonstrate the ways in with biogeography, ecology, and the overlap between these aspects can drive diversification within avian systems.