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 3 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 condit...在北太平洋海域，以鱼类为食的R型“居留型（resident）”虎鲸与以哺乳动物为食的T型“过客型（transient）”虎鲸不存在生殖杂交行为，二者在生态学特征与行为模式上均存在显著差异。本研究对采自北太平洋西部不同区域的12个R型虎鲸样本与14个T型虎鲸样本的全长线粒体基因组（约16.4千碱基对，kbp）进行了测序与组装。所有R型虎鲸个体均携带同一种单倍型（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3种不同的单倍型，其中1种为此前未被记录的新单倍型。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区域。我们将探讨环境条件如何……