Data from: Strong population genetic structure and contrasting demographic histories for the small-spotted catshark (Scyliorhinus canicula) in the Mediterranean Sea

Coastal and demersal chondrichthyans, such as the small-spotted catshark, are expected to exhibit genetic differentiation in areas of complex geomorphology like the Mediterranean Basin because of their limited dispersal ability. To test this hypothesis, we used a fragment of the mitochondrial cytochrome c oxidase subunit I gene and 12 nuclear microsatellite loci in order to investigate the genetic structure and historical demography of this species, and to identify potential barriers to gene flow. Samples were collected from the Balearic Islands, the Algerian Basin, the Ionian Sea, the Corinthian Gulf and various locations across the Aegean Sea. Additional sequences from the Atlantic and the Levantine Basin retrieved from GenBank were included in the mitochondrial DNA analysis. Both mitochondrial and nuclear microsatellite DNA data revealed a strong genetic subdivision, mainly between the western and eastern Mediterranean, whereas the Levantine Basin shared haplotypes with both areas. The geographic isolation of the Mediterranean basins seems to enforce the population genetic differentiation of the species, with the deep sea acting as a strong barrier to its dispersal. Contrasting historical demographic patterns were also observed in different parts of the species' distribution, most notably a population growth trend in the western Mediterranean/Atlantic area and a slight decreasing one in the Aegean Sea. The different effects of the Pleistocene glacial periods on the habitat availability may explain the contrasting demographic patterns observed. The current findings suggest that the small-spotted catshark exhibits several genetic stocks in the Mediterranean, although further study is needed.

以小斑猫鲨（small-spotted catshark）为代表的近岸底栖软骨鱼类（chondrichthyans），因其扩散能力有限，预计在地中海盆地这类复杂地貌区域会出现遗传分化。为验证这一假说，本研究选取线粒体细胞色素c氧化酶亚基I基因（mitochondrial cytochrome c oxidase subunit I gene）片段与12个核微卫星位点（nuclear microsatellite loci），对该物种的遗传结构与历史种群动态展开探究，并识别潜在的基因流（gene flow）阻隔因子。研究样本采集自巴利阿里群岛（Balearic Islands）、阿尔及利亚海盆（Algerian Basin）、爱奥尼亚海（Ionian Sea）、科林斯湾（Corinthian Gulf）以及爱琴海（Aegean Sea）的多个采样点。此外，从基因银行（GenBank）获取的大西洋与黎凡特海盆（Levantine Basin）的序列也被纳入线粒体DNA（mitochondrial DNA）分析。线粒体DNA与核微卫星DNA数据均显示出显著的遗传分化，主要体现在地中海西部与东部海域之间；而黎凡特海盆与这两个区域均共享单倍型（haplotypes）。地中海各海盆的地理隔离似乎强化了该物种的种群遗传分化，其中深海区域构成了其扩散的强力阻隔。在该物种分布的不同区域，还观察到了截然不同的历史种群动态模式：最显著的是地中海西部/大西洋区域呈现种群增长趋势，而爱琴海区域则表现出轻微的种群衰退。更新世冰期（Pleistocene glacial periods）对栖息地适宜性的差异化影响，或可解释上述相悖的种群动态模式。本研究结果表明，小斑猫鲨在地中海海域存在多个遗传种群（genetic stocks），不过仍需开展进一步的研究予以验证。