Genetic differentiation and phylogeography of Mediterranean-North Eastern Atlantic blue shark (Prionace glauca, L. 1758) using mitochondrial DNA: panmixia or complex stock structure?

• DOI: 10.7717/peerj.4112
• Publication Date: 2017-12-06T09:11:25Z
• Authors: Agostino Leone; Ilenia Urso; Dimitrios Damalas; Jann Martinsohn; Antonella Zanzi; Stefano Mariani; Emilio Sperone; Primo Micarelli; Fulvio Garibaldi; Persefoni Megalof...; Luca Bargelloni; Rafaella Franch; David Macias; Paulo Prodöhl; Séan Fitzpatrick; Marco Stagioni; Fausto Tinti; Alessia Cariani
• Keywords: 0301 basic medicine; QH301-705.5; Neuroscience(all); Mediterranean stocks; 590; Sede Central IEO; 551; Biochemistry; /dk/atira/pure/subjectarea/asjc/1300; 03 medical and health sciences; Geographical breaks; /dk/atira/pure/subjectarea/asjc/1300/1300; name=General Biochemistry,Genetics and Molecular Biology; /dk/atira/pure/subjectarea/asjc/1100; Pesquerías; 14. Life underwater; Biology (General); QH426; Blue shark; QL; Agricultural and Biological Sciences(all); mtDNA; /dk/atira/pure/subjectarea/asjc/1100/1100; name=General Agricultural and Biological Sciences; R; Population expansion; Blue shark; Geographical breaks; Mediterranean stocks; mtDNA; Phylogeography; Population expansion; Sharks; Neuroscience (all); Biochemistry, Genetics and Molecular Biology (all); Agricultural and Biological Sciences (all); Geographical break; /dk/atira/pure/subjectarea/asjc/2800/2800; name=General Neuroscience; Phylogeography; mtDNA; Population expansion; Blue shark; Phylogeography; Geographical breaks; Mediterranean stocks; Sharks; Sharks; Aquaculture, Fisheries and Fish Science; Medicine; /dk/atira/pure/subjectarea/asjc/2800; Mediterranean stock; mtDNA, Population expansion, Blue shark, Phylogeography, Geographical breaks, Mediterranean stocks, Sharks; Genetics and Molecular Biology(all)

BackgroundThe blue shark (Prionace glauca, Linnaeus 1758) is one of the most abundant epipelagic shark inhabiting all the oceans except the poles, including the Mediterranean Sea, but its genetic structure has not been confirmed at basin and interoceanic distances. Past tagging programs in the Atlantic Ocean failed to find evidence of migration of blue sharks between the Mediterranean and the adjacent Atlantic, despite the extreme vagility of the species. Although the high rate of by-catch in the Mediterranean basin, to date no genetic study on Mediterranean blue shark was carried out, which constitutes a significant knowledge gap, considering that this population is classified as “Critically Endangered”, unlike its open-ocean counterpart.MethodsBlue shark phylogeography and demography in the Mediterranean Sea and North-Eastern Atlantic Ocean were inferred using two mitochondrial genes (Cytb and control region) amplified from 207 and 170 individuals respectively, collected from six localities across the Mediterranean and two from the North-Eastern Atlantic.ResultsAlthough no obvious pattern of geographical differentiation was apparent from the haplotype network, Φst analyses indicated significant genetic structure among four geographical groups. Demographic analyses suggest that these populations have experienced a constant population expansion in the last 0.4–0.1 million of years.DiscussionThe weak, but significant, differences in Mediterranean and adjacent North-eastern Atlantic blue sharks revealed a complex phylogeographic structure, which appears to reject the assumption of panmixia across the study area, but also supports a certain degree of population connectivity across the Strait of Gibraltar, despite the lack of evidence of migratory movements observed by tagging data. Analyses of spatial genetic structure in relation to sex-ratio and size could indicate some level of sex/stage biased migratory behaviour.