A tale of two seas: contrasting patterns of population structure in the small-spotted catshark across Europe

Chrysoula Gubili,Martin J Genner,Andrew M Griffiths,Ana Veríssimo,Giuseppe Scarcella,Andrew F Johnson,Alen Soldo,David W Sims,Panagiotis Grigoriou,Francis Neat,Matthew Mchugh,Jim Ellis,Bárbara Serra-Pereira,Paolo Domenici,Andrea Satta

doi:10.1098/rsos.140175

Abstract

Elasmobranchs represent important components of marine ecosystems, but they can be vulnerable to overexploitation. This has driven investigations into the population genetic structure of large-bodied pelagic sharks, but relatively little is known of population structure in smaller demersal taxa, which are perhaps more representative of the biodiversity of the group. This study explores spatial population genetic structure of the small-spotted catshark (Scyliorhinus canicula), across European seas. The results show significant genetic differences among most of the Mediterranean sample collections, but no significant structure among Atlantic shelf areas. The data suggest the Mediterranean populations are likely to have persisted in a stable and structured environment during Pleistocene sea-level changes. Conversely, the Northeast Atlantic populations would have experienced major changes in habitat availability during glacial cycles, driving patterns of population reduction and expansion. The data also provide evidence of male-biased dispersal and female philopatry over large spatial scales, implying complex sex-determined differences in the behaviour of elasmobranchs. On the basis of this evidence, we suggest that patterns of connectivity are determined by trends of past habitat stability that provides opportunity for local adaptation in species exhibiting philopatric behaviour, implying that resilience of populations to fisheries and other stressors may differ across the range of species.

Highlights

Molecular genetic markers have had a profound impact in conservation and management [1,2,3]
No significant differences were detected between temporal samples from the Western Channel and all individuals were grouped together into a single sample collection
Pairwise FST values ranged from −0.005 to 0.070 and were significant for all combinations that included the Mediterranean sampling sites, while genetic differentiation was absent among all Northeast Atlantic populations, after Bonferroni correction

Summary

Introduction

Molecular genetic markers have had a profound impact in conservation and management [1,2,3]. Much of the work investigating genetic diversity and population structure of elasmobranchs has been focused on the large pelagic sharks that are considered vulnerable to exploitation in high seas fisheries [16,17]. These species represent a small fraction of the biodiversity of the group. In the Adriatic Sea it has been estimated that the species has declined in abundance by up to 90% since the 1940s [26]

Methods

Results

Discussion

Conclusion