Data from: What influences the worldwide genetic structure of sperm whales (Physeter macrocephalus)?

The interplay of natural selection and genetic drift, influenced by geographic isolation, mating systems and population size, determines patterns of genetic diversity within species. The sperm whale provides an interesting example of a long-lived species with few geographic barriers to dispersal. Worldwide mtDNA diversity is relatively low, but highly structured among geographic regions and social groups, attributed to female philopatry. However, it is unclear whether this female philopatry is due to geographic regions or social groups, or how this might vary on a worldwide scale. To answer these questions, we combined mtDNA information for 1091 previously published samples with 542 newly obtained DNA profiles (394-bp mtDNA, sex, 13 microsatellites) including the previously unsampled Indian Ocean, and social group information for 541 individuals. We found low mtDNA diversity (π = 0.430%) reflecting an expansion event <80 000 years bp, but strong differentiation by ocean, among regions within some oceans, and among social groups. In comparison, microsatellite differentiation was low at all levels, presumably due to male-mediated gene flow. A hierarchical amova showed that regions were important for explaining mtDNA variance in the Indian Ocean, but not Pacific, with social group sampling in the Atlantic too limited to include in analyses. Social groups were important in partitioning mtDNA and microsatellite variance within both oceans. Therefore, both geographic philopatry and social philopatry influence genetic structure in the sperm whale, but their relative importance differs by sex and ocean, reflecting breeding behaviour, geographic features and perhaps a more recent origin of sperm whales in the Pacific. By investigating the interplay of evolutionary forces operating at different temporal and geographic scales, we show that sperm whales are perhaps a unique example of a worldwide population expansion followed by rapid assortment due to female social organization.自然选择与遗传漂变的相互作用，受地理隔离、交配体系及种群规模的调控，决定了物种内部的遗传多样性分布格局。抹香鲸便是一个极具研究价值的案例：作为长寿物种，其扩散过程几乎不存在地理屏障。全球范围内的线粒体DNA（mtDNA）多样性水平相对较低，但在地理区域与社会群体间呈现高度结构分化，这一现象被归因于雌性留居习性（female philopatry）。然而，目前仍不明确该雌性留居习性究竟是由地理区域差异还是社会群体结构所驱动，也不清楚其在全球尺度下的变异规律。为解答上述问题，本研究将1091份已发表样本的线粒体DNA数据，与542份新获得的DNA分型结果（涵盖394 bp的mtDNA序列、性别信息及13个微卫星位点）相结合，其中新增了此前未被采样的印度洋区域样本；同时整合了541个个体的社会群体信息。本研究发现，mtDNA多样性水平较低（核苷酸多样性π=0.430%），反映出距今不足8万年的种群扩张事件；同时，不同大洋间、部分大洋内的区域间以及社会群体间均存在显著分化。相比之下，各级水平的微卫星分化程度均较低，推测这是由雄性介导的基因流所致。层级式分子方差分析（Analysis of Molecular Variance, AMOVA）结果显示，在印度洋区域，地理区域是解释mtDNA变异的重要因素，但在太平洋区域并非如此；而大西洋的社会群体采样规模过小，无法纳入分析。在两大洋内部，社会群体均是划分mtDNA与微卫星变异的关键因素。因此，地理留居习性与社会性留居习性均会影响抹香鲸的遗传结构，但二者的相对重要性因性别与大洋而异，这反映了其繁殖行为、地理特征，或许还与太平洋抹香鲸较晚的起源有关。本研究通过探究不同时间与地理尺度下进化力量的相互作用，揭示出抹香鲸或许是一个独特的案例：全球范围内的种群扩张后，因雌性社会组织驱动而发生了快速的群体结构化分化。