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, due to their limited dispersal ability. To test this hypothesis, we used a fragment of the mitochondrial COI 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, while the Levantine Basin shared haplotypes with both areas. The geograp hic 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.

底栖近海软骨鱼类（如小斑猫鲨（small-spotted catshark））因扩散能力有限，预期在地貌复杂的区域（如地中海盆地）会出现遗传分化。为验证上述假说，本研究采用线粒体COI基因（mitochondrial COI 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，并鉴定潜在的基因流障碍。样本采集自巴利阿里群岛、阿尔及尔盆地、爱奥尼亚海、科林斯湾及爱琴海多处采样点位。此外，从基因银行（GenBank）获取的大西洋与黎凡特盆地序列被纳入线粒体DNA分析。线粒体与核微卫星DNA数据均显示出显著的遗传分化格局，主要分化发生于地中海西部与东部之间，而黎凡特盆地的单倍型（haplotypes）与两个区域均存在共享。地中海盆地的地理隔离似乎强化了该物种的种群遗传分化，深海则构成其扩散的强障碍。研究同时观察到，该物种分布区不同区域的历史种群动态存在显著差异：西地中海/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下降趋势。更新世冰期（Pleistocene glacial periods）对栖息地可获得性的不同影响，或可解释上述相悖的种群动态模式。本研究结果表明，小斑猫鲨在地中海范围内存在多个遗传种群，不过仍需开展进一步研究加以验证。