Honors College Theses

Publication Date

2025

Major

Biology (B.S.B.)

Release Option

Restricted to Georgia Southern

Faculty Mentor

J. Scott Harrison

Abstract

The Amphiuma means (two-toed amphiuma), a large aquatic salamander native to the southeastern United States, may exhibit genetic divergence between mainland and coastal barrier island populations due to restricted gene flow. Gene flow is the transfer of genetic material from one population to another. This study builds on Theisen’s (2023) work by analyzing mitochondrial (cytb) and nuclear (Rag1) DNA from three Georgia locations: Sapelo Island (coastal), Fort Stewart (mainland), and a newly sampled location, Statesboro (mainland). Mitochondrial DNA revealed four haplotypes, with Sapelo Island fixed for a single haplotype (100%), while Fort Stewart and Statesboro showed greater diversity. The significant divergence between Sapelo and Fort Stewart was supported by pairwise PhiPT of mitochondrial cytb data (PhiPT= 0.505, p = 0.001) and AMOVA (40% among-population variation, p = 0.001), suggesting isolation. In contrast, nuclear Rag1 showed lower levels of differentiation (Fst = 0.023, p = 0.082; AMOVA = 1% among-population variation, p = 0.323). These results suggest early divergence between Sapelo Island and Fort Stewart, likely due to barrier island geography. The difference in results between nuclear and mitochondrial loci may be driven by the smaller effective population size and rapid evolutionary rate of mtDNA and/or male-biased migration between populations. The lower genetic diversity on Sapelo Island raises conservation concerns, as small, isolated populations are vulnerable to environmental stochasticity (e.g., hurricanes) and inbreeding depression. This study demonstrates how spatial isolation shapes the genetic structure and highlights the need to monitor isolated amphibian populations facing climate-driven threats.

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