ИСТИНА

Killer whales have been shown to have low diversity of mitochondrial DNA. In the North Pacific, all resident killer whales from Northwest U.S. to Kamchatka have only two haplotypes of the mitochondrial control region. However, sequencing of the complete mitochondrial genomes revealed at least 12 haplotypes in the eastern North Pacific from the Northwest U.S. to the Aleutian Islands. To compare the variation in mitochondrial haplotypes of resident killer whales from Russian waters with those from eastern North Pacific, we sequenced the complete mitochondrial genomes of 12 resident killer whales from the Commander Islands, Kuril Islands and eastern Kamchatka, Russia. We used the long PCR-based approach described in Morin et al. 2010 but on another sequencing platform – Illumina Miseq. For the detection of sequence variation we mapped the reads on the mitochondrial genome of a Commander Islands resident killer whale, Russia (isolate WNPNRRU, NCBI accession number GU187196). We found all individuals had the same complete mitochondrial genome sequence; moreover, it was almost identical to the reference sequence, differing by a 1-bp insertion in the trnN-trnC spacer. Given that this insertion lies in the homopolymer region, it is most likely a sequencing inaccuracy and there is no true difference between our specimens and the reference. The lack of variation in mitochondrial genome sequences of Russian resident killer whales is unusual, because our samples come from different geographical regions, some situated more than 1100 km apart, and population size is relatively large (>700 for Kamchatka, >1000 for Commander Islands). In the eastern North Pacific, different haplotypes were found even in small isolated populations, namely the southern resident population with 80 individuals. The most plausible explanation is the founder effect: we suggest that a small number of resident killer whales have relatively recently colonized the western North Pacific.