北海道から九州に至る43水系で採集された54個体のウグイについて，ミトコンドリア・チトクロムb領域の一部（709bp）の塩基配列を調べた結果，計35のハプロタイプがみられた。平均遺伝子距離は東海－北陸－近幾地方で最も高く，中国および九州地方で最も低く，ハプロタイプ多様度は北海道で最も高く，中国地方で最も低かった。四国地方ではすべてのハプロタイプが本地方のみで見られたものであった。ネットワーク解析では，北海道－東北－関東甲信越－東海北陸近幾・東北－関東甲信越・東海北陸近幾－中国－四国－九州の3群に分かれた。ハプロタイプ系統樹では若狭湾－伊勢湾を結ぶ線を境に大きく東西のグループに分かれたが，糸魚川－静岡構造線を跨ぐハプロタイプが見られた。さらに北上川・熊野川・仁淀川水系などの大河川の上流域に深く分岐した系統が見られることが明らかになった。

This study examined fifty-four samples of Tribolodon hakonensis, collected from 43 river basins in Japan, for genetic relationships based on DNA sequences of a part (709bp) in the mitochondrial cytochrome b region. A total of 35 haplotypes were identified. The average genetic distance was found to be highest in the Tokai-Hokuriku-Kinki region and lowest in the Chugoku and Kyushu regions. Haplotype diversity was highest in the Hokkaido region and lowest in the Chugoku region. In the Shikoku region, all haplotypes were recorded only in this region. Three groups were recognized in the network: Hokkaido, Tohoku, Kanto-Koshinetsu, and Tokai-Hokuriku-Kinki; Tohoku and Kanto-Koshinetsu; and Tokai-Hokuriku-Kinki, Chugoku, Shikoku, and Kyushu. In addition, two large clades were revealed in the genetic tree with a border line connecting the Wakasa Bay in the Sea of Japan side and the Ise Bay on the Pacific Ocean side, although some haplotypes were distributed across the Itoigawa-Shizuoka tectonic line. Furthermore, deeply differentiated lineages were observed in the upper reaches of large river basins, such as the Kitakami, Kumano, and Niyodo River basins.