Estimation of geographical distribution limits between two subspecies of white-spotted charr, Salvelinus leucomaenis imbrius and S. l. pluvius, on the basis of RAPD analysis

RAPD分析に基づき，日本海流入河川のイワナ2亜種，ゴギとニッコウイワナに特異的な遺伝子型の分布を調べることにより，両者の分布境界を推定した。計16断片が増幅され，1個体から7-14バンドが検出されたが，ゴギあるいはニッコウイワナにのみ特異的なバンドは見られなかった。ゴギ，ニッコウイワナ各々9，15のハプロタイプが見られ，これらのうち，2タイプのみが両亜種共通であった。両者が混棲する可能性がある中間域では24ハプロタイプが見られ，これらのうち，5，9タイプがそれぞれゴギ，ニッコウイワナ特異的であった。ゴギ特異的タイプは鳥取県勝田川が東限，ニッコウイワナ特異的タイプは鳥取県日野川が西限であった。日野川水系では17ハプロタイプが見られ，それらのうち，3，7タイプがそれぞれゴギ，ニッコウイワナ特異的であった。クラドグラムではゴギあるいはニッコウイワナ特異的タイプのみからなる大きなクレードは形成されなかった。これらは，ゴギは東方へ，ニッコウイワナは西方へ分布を広げ，その際に大山山塊が両者にとって分布拡大の障壁となったことを示唆する。

We estimated the distribution limits of the 2 subspecies of the white-spotted charr, Salvelinus leucomaenis (‘Iwana’), S. l. pluvius (‘Nikkoiwana’) and S. l. imbrius (‘Gogi’) by examining the distribution of specific genetic types to Nikkoiwana or Gogi in the rivers flowing into the Sea of Japan on the basis of Random Amplified Polymorphic DNA (RAPD). A total of 16 DNA fragments was amplified. Seven to 14 bands were detected from an individual. There were no common bands only to the Nikkoiwana or Gogi. Fifteen and 9 haplotypes were recorded for the Nikkoiwana and Gogi, respectively. Among these, only 2 haplotypes were common to both subspecies. In the intermediate region where both the species were possible to be distributed, 24 haplotypes were detected, among which 9 and 5 types were Nikkoiwana- and Gogi-specific, respectively. Nikkoiwana-specific types were distributed in westernmost to the Hino River, Tottori Prefecture, whereas Gogi-specific types were distributed in easternmost to the Katsuta River, Tottori Prefecture. For the Hino River Basin, 17 haplotypes were detected, among which 7 and 3 types were Nikkoiwana- and Gogi-specific, respectively. In a cladogram, there were no large clades comprising only Nikkoiwana- or Gogi-specific haplotypes. These results suggest westward and eastward range expansions for the Nikkoiwana and Gogi, respectively, and the existence of Mt. Daisen Mountain Mass as a barrier to expansion of both subspecies.