Impacts of a highway on the population genetic structure of a threatened freshwater turtle (Glyptemys insculpta)

Genetic partitions for members of the family Emydidae often correspond with both natural and anthropogenic landforms. For semi-terrestrial turtles, clear negative impacts are associated with habitat fragmentation via roadways, such as loss of breeding individuals, increased inbreeding, and decreased migration. The Wood Turtle (Glyptemys insculpta) is a Species of Special Concern in New York and native to the central portion of the state, where Interstate Highway 88 was constructed in the 1970s. To examine possible impacts of the highway on local populations, a museum collection of Wood Turtles that predates road construction was used. Specifically, microsatellite markers were used to compare historic (n = 38) and contemporary (n = 26) Wood Turtle DNA from opposite sides of the highway. The measured parameters were inbreeding (F-is), differentiation (F-st), number of breeding individuals (N-e), migration (m), and overall population genetic structure. The populations on either side of the highway were predicted to have become more differentiated and inbred over time, and migration was predicted to decrease over time. Overall, populations on either side of the interstate were historically a single population, had a greater number of breeding individuals, and were less differentiated. No change in inbreeding was found across time. These findings suggest there is more migration, running north to south between the two populations, likely attributable to the directionality of the flow associated with local creeks. Further research examining these two separate populations within the context of the entire state is necessary to determine whether they should be treated as separate Conservation Units.