Date of Award

Spring 2026

Document Type

Thesis

Degree Name

Master of Science (MS) in Biology

Department

Biology

Committee Chair

Grover Brown

Abstract

The Southeastern United States is a biodiversity hotspot, and turtles are no exception to the rule. This is particularly true for the genus Sternotherus. Alabama is the only state home to all six species of Sternotherus, including the recently described Intermediate Musk Turtle (Sternotherus intermedius). It was thought that the Perdido River was the western boundary of Sternotherus intermedius; however, surveys in recent years produced questionable individuals in several small watersheds feeding into the Mobile-Tensaw Delta, bringing the species true range into question, as well as the question of if this species has hybridized with its congener, the Stripe-Necked Musk Turtles (S. peltifer) in Mobile and Baldwin Counties, AL. In this study, our objectives were to survey drainages across these two coastal counties for lotic Sternotherus to analyze the populations genetically and morphologically to determine the true geographic distribution and interaction of these species in South Alabama. We were able to collect 71 specimens across 15 different sites. Despite a lack of significant morphological differences, genetic results indicate the presence of S. intermedius in many small Mobile Bay drainages in western Baldwin County (>90% ancestry), and the presence of admixed individuals in Mobile Bay drainages in Mobile County, an area previously believed to be occupied solely by S. peltifer. Further, the hybrid zone between these species extends farther into S. peltifer’s range northward into the Alabama River drainage. These results show that range peripheries can function as active zones of gene flow, refining our understanding of species limits and, more broadly, contemporary evolutionary interactions among closely related species.

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Available for download on Wednesday, October 07, 2026

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