Data from: Global population genetic dynamics of a highly migratory, apex predator shark

Knowledge of genetic connectivity dynamics in the world's large-bodied, highly migratory, apex predator sharks across their global ranges is limited. One such species, the tiger shark (Galeocerdo cuvier), occurs worldwide in warm temperate and tropical waters, uses remarkably diverse habitats (nearshore to pelagic) and possesses a generalist diet that can structure marine ecosystems through top-down processes. We investigated the phylogeography and the global population structure of this exploited, phylogenetically enigmatic shark by using 10 nuclear microsatellites (n = 380) and sequences from the mitochondrial control region (CR, n = 340) and cytochrome oxidase I gene (n = 100). All three marker classes showed the genetic differentiation between tiger sharks from the western Atlantic and Indo-Pacific ocean basins (microsatellite FST > 0.129; CR ΦST > 0.497), the presence of North vs. southwestern Atlantic differentiation and the isolation of tiger sharks sampled from Hawaii from other surveyed locations. Furthermore, mitochondrial DNA revealed high levels of intraocean basin matrilineal population structure, suggesting female philopatry and sex-biased gene flow. Coalescent- and genetic distance-based estimates of divergence from CR sequences were largely congruent (dcorr = 0.0015–0.0050), indicating a separation of Indo-Pacific and western Atlantic tiger sharks <1 million years ago. Mitochondrial haplotype relationships suggested that the western South Atlantic Ocean was likely a historical connection for interocean basin linkages via the dispersal around South Africa. Together, the results reveal unexpectedly high levels of population structure in a highly migratory, behaviourally generalist, cosmopolitan ocean predator, calling for management and conservation on smaller-than-anticipated spatial scales.

当前学界对全球分布的大型、高度洄游的顶级捕食性鲨鱼的遗传连通动力学特征的认知仍存在局限。其中虎鲨（Galeocerdo cuvier）便是这类物种：它们广泛分布于全球暖温带与热带海域，栖息环境跨度极大（从近岸至远洋），且食性泛化，可通过下行调控过程塑造海洋生态系统结构。本研究针对这一遭受过度捕捞、系统发育地位存疑的虎鲨，利用10个核微卫星标记（样本量n=380）、线粒体控制区（CR，n=340）及细胞色素氧化酶I基因（n=100）的序列数据，解析其系统地理学特征与全球种群结构。三类分子标记均显示：西大西洋与印度-太平洋海域的虎鲨种群间存在显著遗传分化（微卫星FST>0.129；线粒体控制区ΦST>0.497）；北大西洋与西南大西洋种群间亦存在分化；且夏威夷海域采集的虎鲨样本与其他调查区域的种群呈现遗传隔离。此外，线粒体DNA分析揭示了大洋内部显著的母系遗传种群结构，暗示雌性存在归巢行为且基因流存在性别偏倚。基于线粒体控制区序列的溯祖分析与遗传距离法得到的分化时间估算结果高度一致（dcorr=0.0015~0.0050），表明印度-太平洋与西大西洋虎鲨种群的分化发生在不足100万年前。线粒体单倍型的系统发育关系显示，西南大西洋可能是跨洋盆种群联系的历史通道——即通过南非周边海域的扩散实现跨洋交流。综合来看，本研究结果表明：这种高度洄游、食性泛化的全球性海洋捕食者，其种群遗传结构的复杂程度远超预期，这要求我们在比此前预想更小的空间尺度上开展虎鲨的管理与保护工作。