Population Structure and Genetic Differentiation in Extant Alligator Snapping Turtles (genus Macrochelys) with Implications for Taxonomy and Conservation

J.J. Apodaca^1,2,*, Alexander R. Krohn¹, Louisa Collins¹, James C. Godwin³, Luke Pearson⁴, and Andrew D. Walde⁵

¹Tangled Bank Conservation, 192 East Chestnut Street, Asheville NC 28801. ²Amphibian and Reptile Conservation, 6844 Bardstown Road, Suite 677, Louisville KY 40291. ³Alabama Natural Heritage Program, Museum of Natural History, Department of Biological Sciences, Auburn University, Auburn AL 36849. ⁴University of Southern Mississippi, 118 College Drive, Hattiesburg MS 39406. ⁵Turtle Survival Alliance 1030 Jenkins Road, Suite D, Charleston SC 29407. *Corresponding author.

Southeastern Naturalist,Volume 22, Special Issue 12 (2023): 1–24

Abstract
Historically believed to harbor unrecognized diversity, the taxonomy of the declining genus Macrochelys (alligator snapping turtles) is debated. The original species, M. temminckii, was recently split into M. temminckii, M. apalachicolae, and M. suwanniensis. However, the status of M. apalachicolae is contested. In this study, we generated thousands of genome-wide loci to quantify population structure and genetic differentiation across the range of Macrochelys spp. Our data indicate that M. apalachicolae is genetically distinct, with little gene flow between M. apalachicolae and other species, thus adding evidence that M. apalachicolae may be a distinct species. We also find genetic variation partitioned among river drainages, with very high intra- and interspecific genetic divergence among river drainages. We suggest that translocations and re-introductions only move turtles in this genus within their natal river drainages to preserve existing patterns of genetic diversity.

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