Date of Award

Summer 2015

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Biology

First Advisor

Dr. Carl Anthony

Abstract

Islands have long fascinated ecologists and evolutionary biologists because they provide replicated systems with which to test hypotheses regarding evolutionary and ecological theory. Because islands are relatively simple systems, they enable researchers to isolate specific factors responsible for observed phenomena. Many current questions in ecology and evolutionary biology have been addressed in island systems. For example, factors involved in the genetic divergence of populations are easier to discern in island populations because confounding effects of gene flow from adjacent populations are limited. This study focuses on isolated island populations of the color polymorphic Eastern Red-backed Salamander (Plethodon cinereus) in the Great Lakes. Morph frequencies of P. cinereus populations on these islands are largely unknown. In addition, it is unknown whether selection or drift may be acting on these populations to drive them toward fixation of one morph or the other. Reports of monomorphic unstriped populations on islands and peninsulas suggest that unstriped individuals may be selected for on islands or in isolated populations. The goal of this project was first to census island populations throughout the Great Lakes to determine morph frequencies on the islands, and second to explore whether island attributes are related to phenotypic differences among island and mainland populations. I compiled morph frequency records from 30 islands and 14 paired mainland sites occurring in each of the five Great Lakes via literature records, museum specimens, and field surveys. In the census, I found that nine islands are polymorphic, two are monomorphic unstriped, and 15 are monomorphic striped. Island elevation above lake level was correlated with morph frequencies. Morph frequencies on taller islands tended to differ more from their mainland source population than on shorter islands. This may be because shorter islands have been more susceptible to flooding post-glaciation and have likely been re-colonized more recently than taller islands. Although it is unclear whether drift or selection are acting on island populations, I detected no evidence that selection is favoring the unstriped morph across all islands.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.

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