Data from: 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 of Gibraltar acts as a barrier to dispersal and that isolation and genetic drift may have had an important role shaping the Mediterranean shark population over time. Analyses of life-history traits allowed the direct comparison among regions providing a complete characterization of this shark population. Sharks from the Mediterranean had markedly smaller adult body size and size at maturity compared to Atlantic and Pacific individuals. Together these results suggest the existence of an isolated and unique population of C. coelolepis inhabiting the Mediterranean that most likely became separated from the Atlantic in the late Pleistocene.

目前学界对限制深海生态系统连通性与基因流（gene flow）的机制认知仍较为匮乏，针对深海鲨鱼的相关研究尤为不足。葡萄牙角鲨（Centroscymnus coelolepis）是一种全球分布、被列为近危（Near Threatened）的深海鲨鱼。本研究采用11个核微卫星标记（nuclear microsatellite markers）与一段长497 bp的线粒体DNA控制区（mtDNA Control Region）片段，对该物种的种群结构进行解析。研究发现大西洋海域内的种群遗传同质化程度极高（ΦST=-0.0091，FST=0.0024，P>0.05），表明该海域仅存在一个大型种群单元。大西洋海域与澳大利亚海域的种群间遗传分化程度较低（ΦST=0.0744，P<0.01；FST=0.0015，P>0.05），进一步表明该物种即便跨越大洋盆地，仍可维持一定程度的遗传连通性。与之形成鲜明对比的是，地中海海域的葡萄牙角鲨种群与所有其他研究区域的种群均呈现出显著的遗传分化（ΦST=0.3808，FST=0.1149，P<0.001）。该结果显示，直布罗陀海峡的较浅水深构成了种群扩散的屏障，且长期的地理隔离与遗传漂变（genetic drift）可能在塑造地中海种群的遗传特征过程中发挥了关键作用。通过对生活史特征的分析，可实现不同区域种群的直接比较，从而完整阐明该鲨鱼种群的生物学特征。相较于大西洋与太平洋的个体，地中海海域的葡萄牙角鲨成体体型及性成熟体型均显著更小。综合上述研究结果，可推断地中海海域存在一个独立且独特的葡萄牙角鲨种群，该种群极有可能在更新世晚期与大西洋种群发生分化隔离。