Genetics and stable isotopes reveal non-obvious population structure of bottlenose dolphins (Tursiops truncatus) around the Balearic Islands

The effective management of wildlife requires that populations are defined in a biological sensible manner. We investigated the population structure of bottlenose dolphins (Tursiops truncatus) in waters around the Balearic archipelago using two complementary techniques; DNA markers (i.e. microsatellites and a portion of the mitochondrial control region) and stable isotopes (δ13C, δ15N). We used tissue samples from biopsies (n = 50) and fresh carcasses (n = 7) obtained around the islands of Gimnèsies and Pitiüses, and Comunitat Valenciana (Western Mediterranean Sea). Genetic differentiation between individuals from Gimnésies and Pitiüses and between individuals from across these two areas and individuals from Comunitat Valenciana was significant when assessing FST, but no substructure was found using clustering methods (i.e. DAPC and Bayesian clustering). δ13C and δ15N profiles were not significantly different between dolphins from Gimnésies and Pitiüses. Dolphins from both areas showed coastal carbon isotopic values and similar trophic niche levels. However, the trophic niche of dolphins from Gimnésies was broader than the trophic niche of Pitiüses’ dolphins. These results indicate non-obvious population structure between the mainland and the archipelago, or between islands within the archipelago. The use of combined techniques, which integrate information over different time scales, is applicable to other species and areas.