Contrasting evolutionary patterns in populations of demersal sharks throughout the western Mediterranean
The spotted catshark (Scyliorhinus canicula) and the blackmouth catshark (Galeus melastomus) are demersal sharks showing a distinct bathymetric distribution in the western Mediterranean. Together, both species represent more than 85% of the total abundance of demersal chondrichthyans in this Mediterranean basin. Our study provides a complete analysis of the genetic population structure, connectivity and demographic history of both species. Sampling was performed across four geographical subareas (GSAs) established by the General Fisheries Commission for the Mediterranean in the western Mediterranean: the northern Alboran Sea (GSA01), Alboran Island (GSA02), Balearic Islands (GSA05) and northern Spain (GSA06). Three mitochondrial fragments were analyzed for both species, and 12 microsatellite loci for S. canicula. We found contrasting patterns of population structure and connectivity in both species. Scyliorhinus canicula displayed significant genetic differences and low connectivity between some GSAs corresponding to different sub-basins (Alboran vs. Balearic). In contrast, G. melastomus showed absence of a population structure and high connectivity between GSAs. These findings are in accordance with the fact that both species exhibit different dispersal behaviors, which leads to distinct bathymetric distributions. Contrasting demographic histories were also identified: Scyliorhinus canicula revealed a recent stable population, with evidence of bottlenecks in the past, which may be related to Pleistocene glacial periods; whereas G. melastomus showed a recent population expansion. Altogether, our findings indicate a mismatch between fishery subareas and population structure for both sharks, which must be considered for fisheries management purposes.
The authors wish to thank all participants in the MEDITS surveys, as well as the crew of R/V Cornide de Saavedra and the Genetics Laboratory team of the Universitat de les Illes Balears. We also thank Dr. Ioanna Manolopoulou for extensive help with the BPEC analyses and Prof. Antonio Amorim for helpful comments. Three anonymous reviewers and the Editor are also greatly acknowledged for their constructive comments in improving the quality of the manuscript.
Compliance with ethical standards
This research was supported in part by the Consejo Nacional de Ciencia y Tecnología (CONACyT) of Mexico, through the FPI Fellowship of SRA, the Direcció General de Innovació i Recerca del Govern de les Illes Balears and the European Regional Development Fund (FEDER), through the Special Actions “Introducción de las técnicas moleculares en la identificación de stocks y conectividad de poblaciones marinas” (AAEE030/2012) and “Mejora de los estudios de diversidad íctica en las Islas Baleares mediante técnicas morfológicas y moleculares” (AAEE7/2015), the project DEMBAGOL funded by the European Commission and the Instituto Español de Oceanografía through the Data Collection Framework and the projects ECLIPSAME and CLIFISH funded by the Spanish Ministry of Economy and Competitiveness (Plan Estatal I + D + I; CTM2012-37701 and CTM2015-66400-C3-1R, respectively). MA was supported by the Fundação para a Ciência e a Tecnologia (FCT) of the Portuguese Government through the FCT Starting Grant IF/00955/2014 and by the Spanish Government through the fellowship “Ramón y Cajal” RYC-2015-18241.
Conflict of interest
All authors declare they have no conflict of interest.
All applicable international, national, and/or institutional guidelines for the care and use of animals were followed.
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