Data from: Colonizing the wild west: low diversity of complete mitochondrial genomes in western North Pacific killer whales suggests a founder effect

In the North Pacific, fish-eating R-type ‘resident’ and mammal-eating T-type ‘transient’ killer whales do not interbreed and differ in ecology and behavior. Full-length mitochondrial genomes (about 16.4 kbp) were sequenced and assembled for 12 R-type and 14 T-type killer whale samples from different areas of the western North Pacific. All R-type individuals had the same haplotype, previously described for R-type killer whales from both eastern and western North Pacific. However, haplotype diversity of R-type killer whales was much lower in the western North Pacific than in the Aleutian Islands and the eastern North Pacific. T-type whales had three different haplotypes, including one previously undescribed. Haplotype diversity of T-type killer whales in the Okhotsk Sea was also much lower than in the Aleutian Islands and the eastern North Pacific. The highest haplotype diversity for both R- and T-type killer whales was observed in the Aleutian Islands. We discuss how the environmental conditions during the last glacial period might have shaped the history of killer whale populations in the North Pacific. Our results suggest the recent colonization or re-colonization of the western North Pacific by small groups of killer whales originating from the central or eastern North Pacific, possibly due to favorable environmental changes after the Last Glacial Maximum.在北太平洋海域中，食鱼性R型“定居型”虎鲸与食哺乳类T型“过客型”虎鲸不存在杂交行为，且二者在生态与行为特征上存在显著差异。本研究对采集自北太平洋西部不同海域的12份R型虎鲸样本与14份T型虎鲸样本，完成了全长线粒体基因组（mitochondrial genome，约16.4 kbp）的测序与组装。所有R型虎鲸个体均携带完全一致的单倍型（haplotype），该单倍型此前已在北太平洋东西部的R型虎鲸种群中被报道。然而，北太平洋西部的R型虎鲸单倍型多样性远低于阿留申群岛（Aleutian Islands）及北太平洋东部种群。T型虎鲸则拥有三种不同的单倍型，其中一种为此前未被记录的全新单倍型。鄂霍次克海（Okhotsk Sea）的T型虎鲸单倍型多样性同样远低于阿留申群岛与北太平洋东部种群。两类虎鲸的最高单倍型多样性均观测于阿留申群岛海域。本研究探讨了末次冰期（Last Glacial Period）的环境条件如何塑造北太平洋虎鲸种群的演化历史。研究结果表明，受末次冰盛期（Last Glacial Maximum）后有利的环境变化影响，源自北太平洋中部或东部的小型虎鲸种群可能近期完成了对北太平洋西部的殖民或再次殖民。