Mitochondrial DNA Variation in the Ouachita Map Turtle
We examined mitochondrial DNA sequence variation among populations of the Ouachita Map turtle (Graptemys ouachitensis ouachitensis), an aquatic species distributed throughout the Mississippi River drainage. We sequenced a 620 base-pair segment of the mitochondrial control region for 65 individuals collected throughout this turtle's range, identifying 18 haplotypes that form two minimally divergent groups. These haplotype groups exhibit substantial range overlap. A presumably disjunct population from the Scioto River in Ohio is represented by both haplotypes groups. The limited genetic differentiation observed suggests that the broad geographic range of haplotypes of G. o. ouachitensis reflects considerable dispersal from two Pleistocene glacial refugia, possibly Mississippi River and Teays River.
Map of the collection localities for Graptemys ouachitensis and G. pseudogeographica. Numbers correspond to those in Table 1. Black circles indicate localities where ouachitensis haplotype group A was observed. White circles indicate localities where only ouachitensis haplotype group B was observed. Gray circles indicate localities where both ouachitensis haplotype groups were observed. Black squares indicate localities where only sabinensis or pseudogeographica haplotypes were observed. The insert map is the approximate species distribution.
Maximum-likelihood tree of haplotypes observed in Graptemys ouachitensis ouachitensis (A1–A11, B1–B7), G. o. sabinensis, and G. pseudogeographica (Gp1–Gp8). Only bootstrap values >50 are reported.
Contributor Notes
Associate Editor: D. Kizirian.