Phylogeography of the north pacific lightfish maurolicus japonicus

A total of 113 and 73 individuals of the North Pacific lightfish Maurolicus japonicus were collected from the Japan Sea and the Pacific Ocean off the Japanese Islands, respectively. Based on nucleotide sequences of mitochondrial genes for cytochrome oxidase c subunit I (COI) and 16S ribosomal RNA, they were classified into the ‘Southern’ clade by Rees et al. (2017). Taken together, the previous results and our present findings suggest that the individuals examined should be treated as a single species, Maurolicus australis, and that this species exhibits the highest genetic diversity in the North Western Pacific Ocean. The Japanese population consisted of three genetically distinct groups. Individuals of one group are also distributed in the South Eastern Atlantic and the Southern Pacific Oceans, and individuals of another group are also distributed in the North Eastern Pacific Ocean. The remaining group has not yet been reported from other sea areas and might be endemic to the North Western Pacific. Although no significant genetic structure was detected around the Japanese Islands, the frequencies of these three groups seemed to show a latitudinal trend.