PhD, University of Cincinnati, 2015, Arts and Sciences: Biological Sciences

The natural world reflects profound biodiversity in every corner of the globe. These phenotypes range from wing spot variation for camouflage in butterflies, to protective armored plates in marine stickleback fish, to extravagant mating displays in peacocks. For many phenotypes, the “selective”?benefit is self-evident. However, some forms of phenotypic evolution?are less obvious, such as regressed or “lost” characters, since it can be difficult to determine the association between a? discarded trait and a selective advantage. Cave-dwelling animals such as the blind Mexican cavefish, Astyanax mexicanus, serve as excellent models to investigate regressive evolution. The surface form is extant, allowing for direct comparisons between river- and cave-dwelling conspecifics. Cavefish likely evolved from an “ancestral” surface-dwelling form, which invaded the caves of Northeastern Mexico. As a consequence of roughly 3 million years in darkness, these remarkable cavefish lost their coloration. Moreover, the recurrent loss of pigmentation in geographically isolated populations renders this system ideal for investigating the broader changes mediating regressive evolution in nature. To investigate these fundamental questions, we utilize an integrative approach to characterize genetic mechanisms contributing to coloration loss in nature. For this, we aimed to describe multiple genetic components – simple traits, complex characters and global changes in gene expression – that may contribute to regressive pigmentation. Although some simple traits (albinism and brown) have been characterized, the roles of cis-regulatory mutations affecting these single locus traits have not been described. We investigated populations of cavefish that harbor “brown” yet depict an intact coding sequence. We discovered many sequence alterations present in the 5' putative promoter region of the causative locus Mc1r, some of which co-localized to highly conserved non-coding elements that may play a c (open full item for complete abstract)

Committee: Joshua Gross Ph.D. (Committee Chair); John Layne Ph.D. (Committee Member); Heather Norton Ph.D. (Committee Member); Kenneth Petren Ph.D. (Committee Member); Stephanie Rollmann Ph.D. (Committee Member) Subjects: Biology