Sarah Kingston

Graduate Student (Ph. D. Candidate)

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Research

My research focuses on hybrid zones between two towhee species, Pipilo maculatus (spotted towhee) and Pipilo ocai (collared towhee), in montane habitat in Mexico. I am interested in the evolutionary importance of introgression of genes across species boundaries and the interaction of hybridization with available habitat. The towhee system is a unique and interesting one to study. Much of the morphological variation and hybridization has been quantified, but very few molecular loci have been investigated. I am interested in applying a genomic approach to assessing the prevalence of introgression in these towhee hybrid zones. Gene or allele frequencies often have a characteristic spatial clinal pattern across a hybrid transect. My goal is to characterize a genomic distribution of cline parameters (e.g. width, center) to characterize the natural variation of these parameters and the implications associated with gene exchange: a steep, narrow cline may suggest a selected locus; a broad, shifted cline may indicate introgression of an allele across species boundaries. In addition, fine-scale DNA sequence-based coalescent analyses can offer estimates of gene exchange between the two species.

A unique characteristic of the towhees in Mexico is an intersection of two different hybrid areas, and an area just south of the peak hybrization where each parental species exists in sympatry, but shows little evidence of hybridization. This special area of sympatry with little to no evidence of hybridization offers an opportunity to contrast the habitats associated with hybridization and lack of hybridization.