日本の野生メダ力における遺伝的撹乱の現状

摘要

We revealed the range and current status of genetic disturbance in Japanese wild medaka populations Oryzias latipes species complex using two DNA markers (b-marker and cytb gene). Genetic disturbances were detected in many wild populations throughout Japan and primarily caused by artificial introgression of the commercial variety called "himedaka". Himedaka genotypes were found frequently around urban areas (Tokyo and Osaka prefecture) and fish farming areas (Nara and Aichi prefecture). The number of himedaka genotypes found from wild population may have been increased according to the high opportunites that himedaka individuals were released into the wild after uses as aquarium fish, teaching materials and conservation activity. In addition, wild populations in some southern islands and Hokkaido prefecture, himedaka genotypes were found with genotypes derived from wild population of Kanto district. This result indicates wild individuals that have himedaka genotypes were transferred from Kanto district. From the result of mitochondrial DNA ND2 analysis, the mitochondrial genotype Bla in Kanto district was different from Bla in other areas, and mey be native genotype in Kanto district. In this study, we identified native populations which may be significant conservation target. To conserve native genetic diversity of medaka, further introduction of himedaka should be prevented by educating the public and users of himedaka about the current status and risks of genetic disturbance.