Historical Biogeography and the Evolution of Migration in Widely Distributed Avian Genera

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9903544 VoelkerThis study addresses the historical biogeography and evolution of migration in four avian songbird genera, each of which is distributed on more than one continent. Relationships among the species in each genus will be determined using mitochondrial DNA sequences, and the results will be used in two ways. First, divergence dates will be applied to the ancestral nodes, when sister-species are determined to have evolved from a common ancestor in a clock-like manner. Using these dates, the biogeographic history of each group will be analyzed to determine the relative roles of dispersal and vicariance in the development of inter-and intracontinental avifaunas. By recognizing that both vicariance and dispersal are well established natural processes, and by attempting to correlate species divergence times with vicariant and dispersal events, more rigorous biogeographic hypotheses will result. This will in turn increase the likelihood that specific isolating mechanisms can be identified within each group, thus increasing our ability to determine whether shared distribution patterns between groups are indeed the result of shared histories. Second, species-specific migratory behaviors will be mapped onto the phylogeny of each group; this mapping method will provide interesting insights into the development of migration within each genus. In addition, this mapping method will generate insights into whether some, all or none of three explicit hypotheses concerning the evolution of avian migration are consistent with the evolution of migration in each of several intercontinentally distributed groups.