title: Phylogeography and population structure of the Dall's porpoise, Phocoenoides dalli, in Japanese waters revealed by mitochondrial DNA.
abstract: We investigated genetic diversity and phylogenetic relationships among three morphologically distinct populations of Dall's porpoise (Phocoenoides dalli) in Japanese waters by analyzing mitochondrial DNA variation. These populations, the Sea of Japan-Okhotsk dalli-type population, the truei-type population and the standard dalli-type population in the northwestern North Pacific, are clearly discriminated from each other by differences in the size of their white flank patch. A total of 479 bp of the mitochondrial control region and flanking tRNA genes was sequenced for 103 individuals. Haplotypic diversity was high (h = 0.968), but these haplotypes differed by only a few nucleotides (pi = 0.0106). Although many haplotypes were shared between populations, analysis of molecular variance (AMOVA) indicated genetic subdivision among the three populations (overall F (ST) = 0.023, P < 0.001; phi(ST) = 0.026, P = 0.029). Pairwise comparisons indicated a low but significant difference between the Sea of Japan-Okhotsk and the other two populations, whereas there was no significant difference between the latter. These results suggest that there is a close evolutionary relationship among these populations despite their consistent differences in coloration. This may reflect genetic polymorphism in the common ancestral population, which subsequently underwent a rapid divergence. The low genetic variability and haplotypic differentiation of the Sea of Japan-Okhotsk population suggest that it originated from a small population that colonized the Sea of Japan or that experienced population reduction when this Sea was isolated from the North Pacific in the last glacial period.
authors.affiliation: Department of Zoology, Graduate School of Science, Kyoto University, Sakyo, Japan. azusa@zoo.zool.kyoto-u.ac.jp
authors.forename: Azusa
authors.initials: A
authors.lastname: Hayano
authors.forename: Masao
authors.initials: M
authors.lastname: Amano
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Miyazaki
mesh_terms: D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D004272:DNA, Mitochondrial; D005260:Female; D014644:Genetic Variation; D005828:Genetics, Population; D005843:Geography; D006239:Haplotypes; D007564:Japan; D008297:Male; D008969:Molecular Sequence Data; D010802:Phylogeny; D010858:Pigmentation / Q000235:genetics; D019576:Porpoises / Q000235:genetics*
chemical_list: D004272:DNA, Mitochondrial