Fine-scale genetic structure of bottlenose dolphins, Tursiops truncatus, in Atlantic coastal waters of the Iberian Peninsula

In the NE Atlantic, evidence has been found of genetic discontinuities between Iberian bottlenose dolphins and those of Scotland and the Mediterranean. Here, we explored the genetic relationships between resident populations of dolphins from southern Galicia (NW Spain) and the Sado estuary (S Portugal), and their relationship with dolphins inhabiting neighbouring areas. A total of 91 skin and muscle samples were taken from stranded and biopsied animals between 1994 and 2008 in southern Galicia (N = 29), the Sado estuary (N = 5) and five other geographical locations (N = 57) including sites around the Iberian Peninsula, the Canary Islands and the Azores. Individuals were genotyped at 10 microsatellite loci and sequenced at the highly variable mitochondrial control region. From individual-based analyses of microsatellite data, dolphins from southern Galicia and the Sado estuary were assigned to an individual genetic population, though nine dolphins were identified as possible migrants between putative populations as their genetic makeup did not correspond with their geographical stranding location. Pairwise estimates of genetic differentiation (F ST) based on mitochondrial and nuclear DNA also revealed genetic differences between populations. The existence of fine-scale population substructure should be considered in the future designation of Special Areas of Conservation (SACs) for the species, as required by the European Habitats Directive.