Population differentiation of the endangered salt-marsh snail Ellobium chinense in Japan (Gastropoda: Ellobiidae)

Ellobium chinense is a red-listed snail species of the family Ellobiidae with a geographic distribution from Vietnam and south coast of China to South Korea and mainland Japan. This species is restricted to specialized habitats in a narrow upper-intertidal to lower-supratidal zone of salt marshes and thus particularly sensitive to environmental degradation through land reclamation and other human activities. Here, we first report the genetic diversity and population structure of E. chinense in Japan to evaluate the connectivity and conservation value of its local populations. Specimens were collected from seven localities (Tsu, Okayama, Yamaguchi, Usa, Imari, Saga and Izumi) that cover the species’ present distribution in the country. Analyses of 612-bp sequences of the mitochondrial cytochrome c oxidase subunit I gene showed high genetic diversity within populations and a reasonable level of connectivity among populations. However, significant genetic differentiation was detected among distant geographic regions in Japan and South Korea, due potentially to the disjunct distribution of habitable salt marshes and a short pelagic larval period of the species. The population of the Ise–Mikawa Bay area, representing the eastern limit of the current distribution range, showed the highest level of genetic differentiation and deserve particular conservation efforts to avoid local extinction, which occurred in Tokyo Bay area in the last century.