Abstract
Three species of Tetraclita, T. squamosa, T. formosana and T. japonica, live in the intertidal zone in Japan. The phylogenetic relationships among them (formerly considered as different subspecies of T. squamosa) were examined in a previous study of Yamaguchi (1987) based not only on comparisons of morphology and geographic distribution, but also on isozyme electrophoresis. In the present study, their interrelationships are examined using parts of the nucleotide sequences of a mitochondrial gene for cytochome oxidase subunit I (COI). In concordance with the results by isozyme electrophoresis, T. formosana and T. japonica are shown to be the closest among the three species. The ancestor of T. formosana and T. japonica, themselves being derived recently, diverged earlier from the last common ancestor of the three species.
