Cytochrome oxidase subunit I (COI) DNA sequence divergence between two cryptic species of Oryzias in South Korea

Abstract

Oryzias latipes and Oryzias sinensis are indigenous species found in Japan, China, and other East Asian countries, includingKorea. Based on morphological differences, the species have been classified distinctly. However, the range ofmorphological characters such as the number of gill rakers, vertebrae, and spots on the lateral body overlaps and is toovague for clear identification, so their classification based on their morphological characteristics remains uncertain. Inthis study, the mitochondrial cytochrome oxidase subunit I (COI) gene, which is used for DNA barcoding, was appliedto clarify interspecific variation of O. latipes and O. sinensis. Intraspecific genetic diversity was calculated to identify correlationswith geographic distributions. We studied two species collected from 55 locations in Korea. All individuals carrieda 679-base pair gene without deletion or insertion. Between species, 525 base pairs of the gene were shared. TheKimura two parameter (K2P) distance of O. latipes and O. sinensis was 0.41% and 1.39%, respectively. Mean divergencewithin genera was 23.5%. Therefore, the species were clearly different. The distance between O. latipes and O. sinensiswas 14.0%, which is the closest within genera. Interestingly O. latipes from the Japanese and Korean group represented16.5% distant. These results were derived from geohistorical and anthropogenic environmental factors. The O. latipeshaplotypes were joined in only one group, but O. sinensis was divided into two groups, one is found in the Han River andupper Geum River watershed; the other is found in the remaining South Korean watersheds. Further studies will addressthe causes for geographic speciation of O. sinensis haplotypes.

Keywords

• cytochrome oxidase subunit I
• geographic distribution
• K2P distance
• Oryzias latipes
• Oryzias sinensis