Snake Venom Composition, Adaptation, and Evolution: Comparative Transcriptomic and Proteomic Analyses of Venoms from the Cottonmouth (Agkistrodon Piscivorus) and the Copperhead (Agkistrodon Contortrix)

• Other Authors: Aronow, Karalyn (authoraut)
• Format: Others
• Language: English; English
• Published: Florida State University
• Subjects: Biology; Life sciences
• Online Access: http://purl.flvc.org/fsu/fd/FSU_migr_etd-8935

Understanding how organisms adapt to their environments is one of the fundamental goals of biology. However, delineating the exact relationships between genotypes, phenotypes, and fitness can be difficult in natural systems. Studying phenotypes that have both simple underlying genetics and direct effects on the survival of an organism can make the connections more clear. The evolutionary patterns of snake venoms and the complete lack of alternative mechanisms of feeding and defense in venomous species makes them an ideal system for studying molecular adaptation and predator-prey coevolution. In chapter one, I investigate the venom-gland transcriptomes of Agkistrodon piscivorus and Agkistrodon contortrix, congeners that have different ecological niches from each other and previously characterized species. Using these congeners as a model system, I will explore the roles of mutational process and selection in venom evolution. I test the hypothesis that A. piscivorus will show higher divergence and strength of selection in toxin gene expression patterns and more gene-family expansion than A. contortrix, due the acquisition of an entirely novel dietary item (fish). Given current knowledge of the evolutionary arms race between venom composition and prey's resistance (Gibbs et al. 2013), A. piscivorus is likely to have toxin gene paralogs that are under strong selection to adapt to a new diet. The test of this hypothesis will provide a direct view of molecular evolution and selection due to novel adaptation in an ecologically critically phenotype. The extraordinarily broad diet of A. piscivorus lends itself to the study of local adaptation, as the most common prey items are unlikely to be found across the entire range of the species. I will investigate the role of expression variation by conducting a detailed analysis of population-level adaptation across the range of a dietary generalist, A. piscivorus. I will test for both ontogenetic and geographic differences in A. piscivorus, focusing on the role of toxin expression variation between life stages and populations. Specifically, I test the hypothesis that A. piscivorus' has population variation in venom composition tied to geographically-based prey availability, given the breath of diet in this species and the strength of selection on venom. === A Thesis submitted to the Department of Biological Science in partial fulfillment of the requirements for the degree of Master of Science. === Summer Semester, 2014. === July 1, 2014. === Adaptation, Agkistrodon contortrix, Agkistrodon piscivorus, Proteomics, Transcriptomes, Venom === Includes bibliographical references. === Darin R. Rokyta, Professor Co-Directing Thesis; Don Levitan, Professor Co-Directing Thesis; Scott Steppan, Committee Member.