Drivers of Population Structure of the Bottlenose Dolphin (Tursiops truncatus) in the Eastern Mediterranean Sea
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The drivers of population differentiation in oceanic high dispersal organisms, have been crucial for research in evolutionary biology. Adaptation to different environments is commonly invoked as a driver of differentiation in the oceans, in alternative to geographic isolation. In this study, we investigate the population structure and phylogeography of the bottlenose dolphin (Tursiops truncatus) in the Mediterranean Sea, using microsatellite loci and the entire mtDNA control region. By further comparing the Mediterranean populations with the well described Atlantic populations, we addressed the following hypotheses: (1) bottlenose dolphins show population structure within the environmentally complex Eastern Mediterranean Sea; (2) population structure was gained locally or otherwise results from chance distribution of pre-existing genetic structure; (3) strong demographic variations within the Mediterranean basin have affected genetic variation sufficiently to bias detected patterns of population structure. Our results suggest that bottlenose dolphin exhibits population structures that correspond well to the main Mediterranean oceanographic basins. Furthermore, we found evidence for fine scale population division within the Adriatic and the Levantine seas. We further describe for the first time, a distinction between populations inhabiting pelagic and coastal regions within the Mediterranean. Phylogeographic analysis suggests that current genetic structure, results mostly from stochastic distribution of Atlantic genetic variation, during a recent post-glacial expansion. Comparison with Atlantic mtDNA haplotypes, further suggest the existence of a metapopulation across North Atlantic/Mediterranean, with pelagic regions acting as source for coastal environments.
KeywordsPopulation structure Phylogeography Tursiops truncatus Mediterranean Sea Gene flow
This research was funded by the Italian DG Fishery within the research framework of the Italian obligations to the Council Regulation (EC) n. 812/2004 (BYCATCH programme). The authors acknowledge the people that have provided samples: Israeli Marine Mammal Research and Assistance Center (IMMRAC, Dan Karem); Blue World Institute, Croatia, Marine Mammals Tissue Bank, University of Padoa, Italy (Bruno Cozzi, Maristella Giurisato); Università degli Studi di Siena, Italy (Letizia Marsili); Morigenos, Slovenia A.R.C.H.E. Porto Garibaldi, Italy (Carola Vallini); Fondazione Cetacea, Italy (Marco Affronte); Tethys Research Institute, Italy (Ada Natoli); Capitaneria di Porto di Brindisi, Italy (Paola Pino d’Astore). We would also like to thank the researchers and volunteers of IMMRAC, Israel.
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