Komaki Shohei, Kurabayashi Atsushi, Islam Mohammed Mafizul, Tojo Koji, Sumida Masayuki
Institute for Amphibian Biology, Graduate School of Science, Hiroshima University, Higashihiroshima 739-8526, Japan.
Zoolog Sci. 2012 Jun;29(6):351-8. doi: 10.2108/zsj.29.351.
Pelophylax nigromaculatus, P. porosus porosus, and P. p. brevipoda are three pond frog species distributed in Japan. Their distributions overlap at two basins in central Japan (P. nigromaculatus and P. p. porosus in the Matsumoto basin, and P. nigromaculatus and P. p. brevipoda in the Ina basin), and hybrid descendants have been found in these areas. To clarify the distribution areas and hybrid zones of the frogs, and to understand the mode of introgressive hybridization and its impact on the frog populations, we conducted exhaustive sampling at each basin and performed allozyme and mtDNA analyses of 233 individuals. Analysis using genetic markers clearly detected nine F1 hybrids and 94 hybrid descendants of P. nigromaculatus and P. porosus from the overlapping areas of both basins. Allozyme and mtDNA data suggest directional hybridization between female P. p. porosus and male P. nigromaculatus in the Matsumoto basin. Over the past 30 years, the distribution of P. p. porosus has been narrowed and fragmented by the invasion of P. nigromaculatus, seemingly because of directional hybridization in the Matsumoto basin. In the Ina basin, the "pure" P. p. brevipoda (n = 8) population was extremely reduced by gene introgression from P. nigromaculatus, yet its distribution was barely changed compared to the Matsumoto basin. Consequently, this study shows that P. porosus populations are threatened by interspecific hybridization with P. nigromaculatus, and that introgressive hybridization damaged P. porosus populations by different means in each basin.
黑斑侧褶蛙、日本林蛙指名亚种和日本林蛙短足亚种是分布于日本的三种泽蛙。它们的分布在日本中部的两个流域重叠（松本流域有黑斑侧褶蛙和日本林蛙指名亚种，伊那流域有黑斑侧褶蛙和日本林蛙短足亚种），并且在这些区域发现了杂交后代。为了阐明这些蛙的分布区域和杂交带，以及了解渐渗杂交的模式及其对蛙种群的影响，我们在每个流域进行了详尽的采样，并对233个个体进行了等位酶和线粒体DNA分析。利用遗传标记进行的分析清楚地检测到来自两个流域重叠区域的9只黑斑侧褶蛙和日本林蛙指名亚种的F1杂交个体以及94只杂交后代。等位酶和线粒体DNA数据表明，在松本流域存在日本林蛙指名亚种雌蛙与黑斑侧褶蛙雄蛙之间的定向杂交。在过去30年里，日本林蛙指名亚种的分布因黑斑侧褶蛙的入侵而变窄并碎片化，这似乎是由于松本流域的定向杂交所致。在伊那流域，“纯种”日本林蛙短足亚种（n = 8）的种群因黑斑侧褶蛙的基因渗入而极度减少，但其分布与松本流域相比几乎没有变化。因此，本研究表明，日本林蛙种群受到与黑斑侧褶蛙种间杂交的威胁，并且渐渗杂交在每个流域以不同方式损害了日本林蛙种群。
