Journal Article
Whole Mitochondrial Genome Analysis of Killer Whales Reveals the Presence of Resident and Transient Ecotypes Around Hokkaido
Momoka Suzuki; Mami Kawai; Takashi Hayakawa; Yuki F. Kita; Yu Sato; Miho Inoue‐Murayama; Akira Shiozaki; Shin Nishida; Shimpei F. Hiruta; Hiroshi Ohizumi; Fumio Nakahara; Shigeo Saino; Yoshikazu Uni; Ayaka T. Matsuda; Takashi F. Matsuishi; Yuko Tajima; Masao Amano; Tadasu K. Yamada; Motoi Yoshioka; Yoko Mitani
Marine Mammal Science · Vol. 42, Issue 1 · 2026
Abstract
In the North Pacific, there are at least three genetically different ecotypes of killer whales ( Orcinus orca ), referred to as resident, offshore, and transient. A previous study suggested that killer whales around Hokkaido belong to fish‐eating (resident and/or offshore ecotypes) and mammal‐eating (transient ecotype) groups. These results were supported by haplotypes based on the combination of 1193 bp of cytochrome b and 420 bp of the control region in mitochondrial genomes. However, this analysis was not sufficient to discriminate between resident and offshore ecotypes because of the short sequence lengths. In this study, we analyzed whole mitochondrial genomes of 25 killer whales sampled around Hokkaido to clarify the ecotypes and mitochondrial genome haplotypes. Phylogenetic analysis revealed the presence of resident and transient ecotypes around Hokkaido. The whales identified as residents shared an identical haplotype, which is the most common haplotype in the western North Pacific. In contrast, the transients around Hokkaido exhibited eight haplotypes, including seven novel ones among the 19 individuals, and their haplotype richness was the highest among the North Pacific populations. This result suggests that the Hokkaido coast served as a refugium for transient killer whales during the Last Glacial Maximum.