美国研究人员日前在《基因组研究》（Genome Research）杂志上报告说，他们对虎鲸线粒体脱氧核糖核酸测序后发现了至少3个新的虎鲸物种，这也表明全球海洋中存在不止一种虎鲸。
由于行为、捕食以及身体特征方面有所不同，研究人员一直怀疑虎鲸并非只有一种。但由于未能对虎鲸进行全基因组测序，他们的怀疑此前未能得到证实。
在新研究中，研究人员通过“高度平行测序技术”对139只虎鲸线粒体的脱氧核糖核酸进行了测序。这批虎鲸来自北大西洋、北太平洋以及南极大陆附近海域。研究人员最终发现，在南极海域生活的两种分别主要以鱼和海豹为食的虎鲸可能属于新物种，此外，北太平洋地区也存在新的虎鲸种群。
领导这项研究的美国国家海洋和大气管理局遗传学家菲利普莫林表示，与其他鲸类一样，虎鲸体内的线粒体也很少随着时间的推移发生变化，因此不查看整个基因组很难发现新进化的虎鲸物种，但利用“高度平行测序技术”可以通过测量来自世界各地的虎鲸组织样本完成对虎鲸线粒体的基因组测序，从而分辨出新物种。
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《基因组研究》发表论文摘要（英文）
Published in Advance April 22, 2010, doi:10.1101/gr.102954.109
Complete mitochondrial genome phylogeographic analysis of killer whales (Orcinus orca) indicates multiple species
Phillip A. Morin1,2,8, Frederick I. Archer1, Andrew D. Foote3,4, Julia Vilstrup3, Eric E. Allen2, Paul Wade5, John Durban5, Kim Parsons5, Robert Pitman1, Lewyn Li6, Pascal Bouffard6, Sandra C. Abel Nielsen3, Morten Rasmussen3, Eske Willerslev3, M. Thomas P. Gilbert3 and Timothy Harkins7
Killer whales (Orcinus orca) currently comprise a single, cosmopolitan species with a diverse diet. However, studies over the last 30 yr have revealed populations of sympatric “ecotypes” with discrete prey preferences, morphology, and behaviors. Although these ecotypes avoid social interactions and are not known to interbreed, genetic studies to date have found extremely low levels of diversity in the mitochondrial control region, and few clear phylogeographic patterns worldwide. This low level of diversity is likely due to low mitochondrial mutation rates that are common to cetaceans. Using killer whales as a case study, we have developed a method to readily sequence, assemble, and analyze complete mitochondrial genomes from large numbers of samples to more accurately assess phylogeography and estimate divergence times. This represents an important tool for wildlife management, not only for killer whales but for many marine taxa. We used high-throughput sequencing to survey whole mitochondrial genome variation of 139 samples from the North Pacific, North Atlantic, and southern oceans. Phylogenetic analysis indicated that each of the known ecotypes represents a strongly supported clade with divergence times ranging from &150,000 to 700,000 yr ago. We recommend that three named ecotypes be elevated to full species, and that the remaining types be recognized as subspecies pending additional data. Establishing appropriate taxonomic designations will greatly aid in understanding the ecological impacts and conservation needs of these important marine predators. We predict that phylogeographic mitogenomics will become an important tool for improved statistical phylogeography and more precise estimates of divergence times.
