Genetic evidence supporting the existence of two distinct species in the genusGasterosteus around Japan

• DOI: 10.1007/bf00002375
• Publication Date: 2004-12-17T05:58:19Z
• Authors: Masahito Higuchi; Akira Goto
• Keywords: Reproductive isolation

The genetic and morphological features ofGasterosteus aculeatus were investigated for 29 populations around Japan. Allozyme analyses recognized two groups (Pacific Ocean group and Japan Sea group) that had distinct characteristic features, and showed high genetic differentiation between them (D = 0.482). The Pacific Ocean group had a wide range, from North America to Japan, along the Pacific coast. The distribution of the Japan Sea group was limited around the Sea of Japan and the Sea of Okhotsk. The distribution of these groups were found to be sympatric on the Pacific coast of Hokkaido Island, Japan. From this area, genetic analyses demonstrated that the sympatric populations of the two groups formed independent breeding stocks, and it is considered that the two groups were reproductively isolated from each other. Additionally, each group had distinctive morphological features of lateral plates and caudal keels in the sympatric area. These results suggested that these two groups of the threespine stickleback comprise different species and that the Japan Sea group is taxonomically distinguishable fromG. aculeatus.