Population genetic structure of a disjunct population of Blanding’s turtle ( Emydoidea blandingii) in Nova Scotia, Canada

Abstract

The Nova Scotia population of Blanding’s turtle ( Emydoidea blandingii) is small and disjunct but surprisingly contains spatial structure. In this paper we explore the nature of that structure and attempt to identify the processes underlying it. Recent studies of the species in Nova Scotia have identified three discrete groups in what was previously thought to be a single panmictic population. There is no evidence of current movement between these groups. One group, at Kejimkujik National Park and National Historic Site, is restricted to the Mersey watershed; the other two groups are on the adjacent Medway watershed. The lack of current movement led to the prediction that there might be measurable genetic structure among these groups. Microsatellite analysis of five loci revealed significant genetic structure ( F ST = 0.042–0.124; p < 0.05) in pairwise comparisons between groups. Distance rather than watershed appears to be the principal determinant of spatial structure. Two separate analyses reveal no evidence of recent population bottlenecks. Population simulations suggest that this differentiation likely pre-dated human influence on the local landscape. In the face of rapid environmental change, understanding spatial structure in this population complex is essential so that we can match management scale to ecological scale in this long-lived, late maturing species.