Unexpectedly low genetic divergences among populations of the threatened bog turtle (Glyptemys muhlenbergii)

Abstract

We used mitochondrial DNA sequence comparisons to assess range-wide population structure and historical patterns of differentiation among populations of the bog turtle (Glyptemys muhlenbergii). This species is one of North America's smallest and most endangered pond turtles, and is currently found in three largely disjunct groups of populations: in the southern U.S., in the northeast, and in the Finger Lakes and Lake Ontario Plains region of western and central New York State. All the New York sites and most of the northeastern sites were glaciated during the Pleistocene. We surveyed 2793 bases pairs of mitochondrial DNA spanning three genes (cytb, nd4, and d-loop) in 41 individuals from 21 populations throughout most of the bog turtle's distribution. We found surprisingly low levels of divergence among populations, even in southern populations that have been hypothesized as refugia during times of climate change. Our data suggest populations of bog turtle's suffered a bottleneck, followed by a rapid post-Pleistocene expansion into northern segments of the species' range. We discuss historical changes in habitat availability and climate that may have influenced the historical deployment of lineages in this species, and possible life history traits and habitat dynamics that might also contribute to the overall low genetic diversity across its range. © 2007 Springer Science+Business Media B.V.