Data from: Genetic diversity of white sharks, Carcharodon carcharias in the Northwest Atlantic and southern Africa.

The white shark, Carcharodon carcharias, is both one of the largest apex predators in the world and among the most heavily protected marine fish. Population genetic diversity is in part shaped by recent demographic history and can thus provide information complementary to more traditional population assessments, which are difficult to obtain for white sharks and have at times been controversial. Here, we use the mitochondrial control region and 14 nuclear encoded microsatellite loci to assess white shark genetic diversity in two regions: the Northwest Atlantic (NWA, N=35) and southern Africa (SA, N=131). We find that these two region harbor genetically-distinct white shark populations (ΦST=0.10, p<0.00001; microsatellite FST=0.1057, p<0.021). M-ratios were low and indicative of a genetic bottleneck in the NWA (M-ratio=0.71, p<0.004) but not SA (M-ratio= 0.85, p=0.39). This is consistent with other evidence showing a steep population decline occurring in the mid to late 20th century in the NWA, while the SA population appears to have been relatively stable. Estimates of effective population size ranged from 22.6-66.3 (NWA) and 188-1998.3 (SA) and evidence of inbreeding was found (primarily in NWA). Overall, our findings indicate that white population dynamics within NWA and SA are determined more by intrinsic reproduction than immigration and there is genetic evidence of a population decline in the NWA, further justifying the strong domestic protective measures that have been taken for this species in this region. Our study also highlights how assessment of genetic diversity can complement other sources of information to better understand the status of threatened marine fish populations.

噬人鲨（Carcharodon carcharias，俗称大白鲨）既是全球体型最大的顶级捕食者之一，也是受保护程度最高的海洋鱼类类群之一。种群遗传多样性在一定程度上受近期种群历史动态塑造，因此可提供与传统种群评估互为补充的信息；而针对大白鲨的传统种群评估不仅难以开展，有时还颇具争议。
本研究依托线粒体控制区序列与14个核编码微卫星位点，对两个区域的大白鲨遗传多样性展开评估：西北大西洋（NWA，样本量N=35）与南非海域（SA，样本量N=131）。
研究发现，这两个区域的大白鲨种群存在显著遗传分化（ΦST=0.10，p<0.00001；微卫星FST=0.1057，p<0.021）。
西北大西洋种群的M指数偏低，提示其曾经历遗传瓶颈（M-ratio=0.71，p<0.004），而南非种群则无此特征（M-ratio=0.85，p=0.39）。
这一结果与其他证据相吻合：20世纪中后期西北大西洋大白鲨种群曾出现急剧下降，而南非种群则相对稳定。有效种群大小估算值范围为：西北大西洋22.6~66.3，南非188~1998.3；同时研究发现了近交现象，且主要集中于西北大西洋种群。
综上，本研究结果表明，西北大西洋与南非海域的大白鲨种群动态更多由内在繁殖过程而非种群迁入所决定；同时遗传学证据证实西北大西洋种群曾出现衰退，这进一步为该区域针对该物种实施的严格本土保护措施提供了科学依据。
本研究同时凸显了遗传多样性评估可如何补充其他信息来源，以更好地了解受威胁海洋鱼类种群的生存现状。