Date of Award

8-2024

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biological Sciences

Committee Chair/Advisor

Christopher L. Parkinson

Committee Member

Samantha Price

Committee Member

Matthew Koski

Abstract

Complex traits, such as body size and venom, are often under strong selection by

dietary ecology and can increase efficiency of prey capture and processing. To investigate relationships between ecology and trait evolution in Thamnophis, we amassed nearly 10,000 diet records for 32/35 Thamnophis species and classified each species’ dietary repertoire. We categorized 15/32 species as generalist predators and 17/32 species as specialist predators of varying prey groups and investigated the hypothesis that generalist predators have larger body size. However, we found no significant relationship between body size and dietary specialization. Venom has evolved over 100 times across the Tree of Life and is a key component of prey capture and predator defense. While many studies on snake venom have been conducted investigating the evolutionary relationship between venoms and diet, they have focused on medically-relevant front fanged snakes. Recently, venom characterization has spread to non-front fanged snakes; however, many are only descriptive. To uncover evolutionary pressures impacting venom characteristics in Thamnophis, we sequenced, annotated, and analyzed Duvernoy’s venom gland transcriptomes from 16 species. We generated measures of complexity of toxins and dietary records and found strong correlations between the complexity of toxin expression and phylogenetic diversity of diet. We suggest that, in non-front fanged snakes, the expression of toxins is under selection by dietary diversity rather than transcriptomic complexity, contradicting studies from front-fanged snakes. Additionally, our findings add to knowledge of natural history, ecology, and evolution of Thamnophis and assembled the largest dietary record repository for the genus to date.

Author ORCID Identifier

0009-0008-2480-7323

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