Lyrholm T, Leimar O, Johanneson B, Gyllensten U
Department of Zoology, Stockholm University, Sweden.
Proc Biol Sci. 1999 Feb 22;266(1417):347-54. doi: 10.1098/rspb.1999.0644.
The social organization of most mammals is characterized by female philopatry and male dispersal. Such sex-biased dispersal can cause the genetic structure of populations to differ between the maternally inherited mitochondrial DNA (mtDNA) and the bi-parental nuclear genome. Here we report on the global genetic structure of oceanic populations of the sperm whale, one of the most widely distributed mammalian species. Groups of females and juveniles are mainly found at low latitudes, while males reach polar waters, returning to tropical and subtropical waters to breed. In comparisons between oceans, we did not find significant heterogeneity in allele frequencies of microsatellite loci (exact test; p = 0.23). Estimates of GST = 0.001 and RST = 0.005 also indicated negligible if any nuclear DNA differentiation. We have previously reported significant differentiation between oceans in mtDNA sequences. These contrasting patterns suggest that interoceanic movements have been more prevalent among males than among females, consistent with observations of females being the philopatric sex and having a more limited latitudinal distribution than males. Consequently, the typical mammalian dispersal pattern may have operated on a global scale in sperm whales.
大多数哺乳动物的社会组织特征为雌性留居和雄性扩散。这种性别偏向性扩散会导致种群的遗传结构在母系遗传的线粒体DNA（mtDNA）和双亲遗传的核基因组之间存在差异。在此，我们报告抹香鲸海洋种群的全球遗传结构，抹香鲸是分布最广泛的哺乳动物物种之一。雌性和幼年抹香鲸群体主要分布在低纬度地区，而雄性则会到达极地水域，之后返回热带和亚热带水域进行繁殖。在不同大洋之间的比较中，我们未发现微卫星位点等位基因频率存在显著异质性（确切检验；p = 0.23）。GST = 0.001和RST = 0.005的估计值也表明，即使存在核DNA分化，其程度也可忽略不计。我们之前曾报道不同大洋之间mtDNA序列存在显著分化。这些截然不同的模式表明，雄性的跨洋移动比雌性更为普遍，这与雌性为留居性别且纬度分布范围比雄性更有限的观察结果一致。因此，典型的哺乳动物扩散模式可能在全球范围内适用于抹香鲸。
