The tideland snails Pirenella nipponica and Pirenella asiatica are distributed north of the central Ryukyu Islands and in South Ryukyu, respectively, in Japan. To reveal their distribution and genetic characteristics in Taiwan, we sampled Pirenella snails along the western coast of Taiwan Island and analyzed the nucleotide sequences of their mitochondrial DNAs. Pirenella nipponica and P. asiatica inhabit the northern and southern parts of the western coast of Taiwan, respectively, and coexist only in the central part. Taiwanese and Japanese populations of P. asiatica showed significant genetic differentiation. The former showed higher genetic diversity and a larger effective population size than the latter. However, the Taiwanese population of P. nipponica was not genetically deviated from the local Japanese population on Kyushu Island. Both the Taiwan and Kyushu populations of P. nipponica showed significant genetic differences from local populations in other regions of Japan, namely, Honshu Island (the Japanese mainland) and Central Ryukyu. They also showed higher genetic diversity and a larger effective population size than the others. The Taiwanese populations of both species might be part of a large panmictic
population with individuals from the Asian continent and Kyushu Island.
Tideland snail, Pirenella, Taiwan Island, Nansei Islands, Phylogeography.
