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

目的：阐明一种濒危淡水贻贝的生物多样性并制定保护计划。本研究分析了玛格丽缇贝（Margaritifera laevis）、当地种群的遗传多样性、各地方种群的生境偏好以及该贻贝舌部与鲑科物种之间的宿主-寄生虫关系。等位酶和mtDNA分析显示A和B两个高度分化的类群，在对称分布的类群之间没有杂交的证据，表明它们之间存在生殖隔离。在遗传多样性方面，A组群体间存在较大的遗传变异，而B组群体间不存在遗传变异。利用特异性mtDNA标记对glochia的种类鉴定表明，A组glochia只寄生于masou Oncorhynchus的鳃，而B组glochia寄生于Salvelinus leucomaenis和S. malma的鳃。野外生态调查结果表明，水流和底质是限制两类小鲵生存的重要环境因子。为了保护这两个种群，本研究提出了一个积极的保护计划，包括维持良好的宿主-寄生虫结合和恢复良好的河底环境，使glochidia能够在此定居。

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.