Doctor of Philosophy (PhD)


Biological Sciences

Document Type



Modern phylogenetic methods and molecular data can be powerful tools for examining the evolution of organisms. Of particular interest are historical processes that influenced the diversity and distribution of modern taxa. I examined the evolutionary history of two families of birds, the barbets and toucans (Ramphastidae) and the trogons (Trogonidae). Both groups occur in three disjunct tropical regions, a pattern that offers no simple historical explanation. In addition to their distributions, these two families are also similar in that they are relatively ancient groups but have highly conserved and distinctive morphologies. DNA sequence data do not produce concordant phylogenies for the two families. However, data incongruence and model misspecification in the trogon data set limited phylogenetic resolution and precluded inferences about trogon historical biogeography. In contrast, the molecular data from the barbets yielded a highly resolved phylogeny supporting monophyly of barbets from each tropical region. Pairwise divergence estimates and fossil evidence support an Old World origin for the family. Two genera (Trachyphonus and Calorhamphus) diverged from other barbets relatively early and have no close living relatives, but most lineages arose more recently. I studied one of those lineages, the African tinkerbirds (Pogoniulus), in more detail to examine speciation patterns and geographic differentiation in Africa. The tinkerbirds exhibit a pattern of early differentiation between habitat types and subsequent differentiation within those habitats. This pattern of differentiation does not conform to any single speciation model for African birds. In addition, all species with geographic representation show evidence of substantial genetic differentiation between populations.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Frederick H. Sheldon