Molecular Population Genomics:
My laboratory is interested in the genomic processes that alter gene and chromosomal frequencies in natural populations of plants and animals.

Specifically, we use genetic markers distributed across chromosomes to determine how evolutionary forces alter the frequencies of chromosomes in natural populations. Our current research is examining markers on the X and 3rd chromosome of Drosophila pseudoobscura, two chromosomes that have inversion polymorphisms segregating in natural populations, to determine how selection alters inversion frequencies in populations.

We have recently published a study of five X-linked genes in 40 strains of Drosophila pseudoobscura. The X chromosome has a rather simple inversion system with only two inversion types, Standard and Sex Ratio. The X chromosome is tranmitted predominantly in males that carry the Sex Ratio inversion leading to 95-100 % female offspring. This study used X-link markers to determine if selection operates on any on the genes, how much gene flow occurs in this species, and how much genetic exchange occurs among loci.

One of the interesting findings from this work was that the Est-5 gene had significantly less diversity in Sex Ratio chromosomes compared to the four other genes examined in this study. In addition, the majority of polymorphic nucleotide sites within Est-5 were in linkage disequilibrium with the Sex Ratio phenotype. These data suggest that the Est-5 gene is quite close to the gene or genes that are responsible for the Sex Ratio phenotype.

The laboratory has sequenced eight genes from 80 to 100 D. pseudoobscura strains that differ in the paracentric inversions that they carry. This experiment is designed to be a natural quantitative trait locus (QTL) experiment to map the genes that have been targets of natural selection.

Ecological Genetics:
My laboratory is also involved with collaborative projects with Dr. Charles R. Fisher to understand the ecological and genetic factors that shape the communities at cold seeps and hydrothermal vents. Experimental and theoretical approaches in population genetics are being used to determine how much gene flow occurs among cold seep habitats in the Gulf of Mexico. We have examined the ecological forces that shape communities of tubeworms at the East Pacific Rise (EPR). Three species of tubeworms are found along the EPR that colonize the vents in a successional pattern. The laboratory developed an RFLP assay that can distinguish among the three tubeworm species, which cannot be identified to species with morphological examination. This study found that colonization of vents by Tevnia jerichonana facilitates the colonization of Riftia pachyptila and Oasisia alvinae. Future directions will include a study of the genetics of the morphology of hydrothermal vent tubeworms.