Keith Barker, PhD, University of Minnesota
BEES Ornithology Interview Research Seminar: "Top-Down and Bottom-up Approaches to Understanding Avian Diversification: Lessons From Passerine Birds"
Abstract: Diversification of lineages is often analyzed at a global scale, which may prevent identification of locally successful lineages that have not diversified impressively from a global perspective. On the other hand, analyzing among-lineage patterns of diversification on geographically relevant scales is complicated by dispersal, especially in a group with high dispersal potential such as birds. I take a regional perspective on global diversification dynamics of oscine passerines, by inferring interhemispheric (Old World-New World) interchanges, estimating the timing of these dispersal events, and comparing post-dispersal net diversification of dispersing lineages. Most lineages arriving in the New World have diversified on a trajectory consistent with a constant-rates birth-death process with a relatively high extinction fraction. By contrast, several relatively old North American lineages have not diversified at all, and one widely-distributed lineage--the Emberizoidea--has diversified at a rate far exceeding comparably-aged New World lineages. I further analyze emberizoid diversification and show that, while this lineage has experienced extraordinary success overall, this masks complex variation among specific lineages. These analyses are crude steps toward placing avian diversity into a more realistic geographic context. However, these improvements offer significant insights into the evolution of avian diversity. Future, more fine-grained analyses enabled by more complete and robust phylogenies will offer even better.