Term of Award

Fall 2017

Degree Name

Master of Science in Biology (M.S.)

Document Type and Release Option

Thesis (open access)

Copyright Statement / License for Reuse

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.


Department of Biology

Committee Chair

Christian Cox

Committee Member 1

Lance McBrayer

Committee Member 2

John Schenk


Color polymorphism in aposematic mimicry systems is a perplexing phenomenon for evolutionary biologists, as theoretically the benefits of converging on a model phenotype should constrain the evolution of phenotypic diversity in these systems (i.e., color polymorphism should not occur). Nevertheless, color polymorphism in mimicry systems is prevalent throughout many taxa. In some of these systems, the evolution of color polymorphism results in the existence of non-mimetic morphs, such as those that are cryptic. The case of ground snakes (Sonora semiannulata) is unique in that color polymorphism encompasses both mimetic and cryptic morphs, as well as individual mimetic and non-mimetic traits. In this study, I used ground snakes to investigate the evolutionary drivers of polymorphic non-mimetic traits within a mimicry system. With a robust dataset of 1240 individuals from 49 populations, I assessed spatial patterns of color traits and associations among them. In addition, I utilized high-throughput DNA sequencing to generate 2,125 neutral single-nucleotide polymorphisms (SNPs) shared among 109 individuals, which allowed me to conduct population genetic analyses that, in turn, shed light on selective processes. I demonstrated that mimetic and non-mimetic polymorphic traits are spatially linked with one another, but that they appear to be influenced by different patterns of selection. These results, when taken together, offer support for genetic linkage between these different types of color polymorphism. Such findings present a novel mechanism by which phenotypic diversity can be maintained, which has major implications for color pattern diversity across the tree of life.

Research Data and Supplementary Material