The Pillars of Hercules as a bathymetric barrier to gene-flow promoting isolation in a global deep-sea shark (Centroscymnus coelolepis)

Knowledge of the mechanisms limiting connectivity and gene-flow in deep-sea ecosystems is limited, especially for deep-sea sharks. The Portuguese dogfish (Centroscymnus coelolepis) is a globally distributed and Near Threatened deep-sea shark. C. coelolepis population structure was studied using 11 nuclear microsatellite markers and a 497 bp fragment from the mtDNA Control Region. High levels of genetic homogeneity across the Atlantic (ΦST=-0.0091, FST= 0.0024, P > 0.05) were found suggesting one large population unit at this basin. The low levels of genetic divergence between Atlantic and Australia (ΦST= 0.0744, P<0.01; FST=0.0015, P > 0.05) further suggested that this species may be able to maintain some degree of genetic connectivity even across ocean basins. In contrast, sharks from the Mediterranean Sea exhibited marked genetic differentiation from all other localities studied (ΦST=0.3808, FST=0.1149, P < 0.001). This finding suggests that the shallow depth of the Strait...