Research

My research focuses on avian diversity and evolution, and my interests encompass studies of geographic population structure, gene flow, introgression, hybridization, phylogeography, speciation, biogeography, systematics, and phylogenetics. Specifically I am interested in how geographic differentiation, both in genes and morphology, develops, is maintained, and ultimately works to produce new species. For many questions, I get to combine field, museum and molecular approaches.

Current research projects:

Phylogeography of the Yellow-throated Warbler
Molecular Ecology of House Finches
Manakin (Pipridae) Phylogenetics

Phylogeography of the Yellow-throated Warbler

For my thesis, I am studying the population genetic structure of a widespread southern wood-warbler, the Yellow-throated Warbler. Yellow-throated Warblers show an interesting pattern of subtle morphological differentiation mostly involving bill lengths. In western portions of their range bills are short, whereas in the east they are medium. Two additional disjunct long-billed forms occupy similar habitats on opposite sides of the Yellow-throated Warbler range: one on the Delmarva Peninsula and one along the Gulf Coast. I am using molecular tools to infer the evolutionary histories of these distinct populations in order to determine 1) whether the disjunct long-billed forms are related or are the product of parallel evolution (perhaps an adaptive response to a similar habitat), 2) the position of the Yellow-throated Warbler in a larger comparative phylogeographic framework especially concerning a mysterious vicariant event that has affected this species, Carolina Chickadees, and Northern Parulas as well as some fish and herps, and 3) the level of genetic distinctiveness of these populations and thus their value as units of conservation.

In addition to my thesis work with Yellow-throated Warblers, I am involved in several side projects.

Molecular Ecology of House Finches

The House Finch (Carpodacus mexicanus) is native to the western United States and Mexico. Upon the arrival of Europeans to North America, introduced populations of House Finches appeared in New York City and Hawaii. The small founding population of New York City has subsequently spread and now occupies much of the eastern United States. A new House Finch disease, Mycoplasma gallicepticum, recently swept through the eastern House Finch population. It has been suggested that eastern populations were more susceptible to the epidemic due to decreased genetic diversity following a founding effect.

Empirical studies of this have produced mixed results, so I, in collaboration with Herman Mays, am using mtDNA to look at haplotype diversity in the eastern population. If the eastern population was, as is assumed, founded by few genetically uniform individuals, we expect very few haplotypes compared with western populations, which we are also sampling. For comparasion, we are also looking at haplotype diversity in the Hawaii population. The Hawaii population was also founded by few birds, and there is less chance that this population has had subsequent gene flow with the mainland.

In addition, we have obtained museum toe pad samples from every subspecies including the threatened and endangered ones, so we are also working on a phylogeographic study of the House Finch. We are using mtDNA to infer relationships and relative divergence times of subspecies. This is important not only to understand the recent evolutionary history of this species but also the conservation priory of the rare subspecies.

Manakin (Pipridae) Phylogenetics

In collaboration with Herman Mays and Stephanie Doucet, I have sequenced the cytochrome oxidase I (COI) mtDNA gene from manakin samples collected by Stephanie and supplemented by the LSU Museum of Natural Science to create a preliminary phylogenetic hypothesis for the Pipridae. This family shows remarkable diversity in mating systems and is the focus of much comparative work, so I was amazed to discover that no molecular phylogeny for this group had been published. Using the CO1 gene, we have put together a well-supported phylogenetic tree that includes 12 of the 15 manakin genera. We don’t mean for this project to be the final word on the evolutionary relationships of manakins, but we hope that it will serve as a temporary molecular phylogenetic hypothesis for this group and a starting point for future researchers to develop a more in-depth molecular phylogeny.