Genetic and ecological diversity of a rare freshwater pearl mussel Margaritifera laevis with reference to its conservation plan

阐明濒危淡水贻贝的生物多样性并制定保护计划。本研究对花斑贻贝本地种群的遗传多样性、各种群的栖息地偏好以及该贻贝的钩体与鲑科鱼类的寄主-寄生关系进行了研究，获得了以下结果。等位酶和线粒体DNA分析表明，A、B两个群体间没有杂交证据，表明它们之间存在生殖隔离。在遗传多样性方面，A组在种群间表现出较大的遗传变异，而B组则没有表现出任何遗传变异。利用mtDNA特异标记对钩虫进行物种鉴定，结果表明A组的钩虫只寄生在文昌鱼的鳃上，而B组的钩虫只寄生在亮鳞鱼和马尔玛的鳃上。野外生态调查结果表明，水流和底质是制约两组黄姑鱼生存的重要环境因子。为了保护两个种群的当地种群，本研究提出了一项积极的保护计划，包括保持良好的寄主-寄生虫联合和恢复良好的溪底条件，使钩虫能够在其上定居。

To elucidate the biological diversity and make a conservation plan for an endangered freshwater mussel. Margaritifera laevis, the genetic diversity of the local populations, habitat preference of each local population and host-parasite relationships between the glochidia of this mussel and salmonid species were examined in this study and the following results were obtained.1. Allozyme and mtDNA analyses revealed two highly divergent groups (Group A and B) with on evidence of hybridization between the groups which were sympatrically distributed, suggesting the existence of reproductive isolation between them. As for genetic diversity, group A showed considerable genetic variations among populations, whereas group B showed no any genetic variation.2. Species identification of glochidia by using specific mtDNA markers indicated that the glochidia of group A parasitized only the gill of Oncorhynchus masou, whereas those of group B parasitized the gill of Salvelinus leucomaenis and S. malma.3. The field ecological survey revealed that water current and bottom substratum were important environmental factors limited to survival for the two groups of M laevis.4. To conserve the local populations of two groups of M. laevis, an active conservation plan including the maintenance of good host-parasite association and restoration of good stream bottom conditions on which the glochidia were possible to settle down was proposed in this study.