Molecular Species Delimitation of the Genus Reishia (Mollusca: Gastropoda) Along the Coasts of China and Korea

Species of the predatory gastropod genus Reishia Kuroda and Habe, 1971 (Muricidae) inhabit intertidal rocky shores in East Asia. Due to their highly variable external shell morphology, the taxonomy of this genus at species-level is still in need of re-evaluation. Using DNA-based delimitation methods, we aimed to ascertain the number of species of Reishia along the coasts of China and adjacent Asian areas. Also, we looked for diagnostic traits using morphology-based statistical approaches. Our genetic data suggest that the studied individuals comprised two separate species of a Reishia complex in this region, in contrast to the previously proposed four or more taxa. This conclusion is further supported by statistical analyses of shell morphological characteristics. The morphospecies R. bronni (Dunker, 1860), R. jubilaea (Tan and Sigurdsson, 1990), and R. luteostoma (Holten, 1803) were assigned to a single taxon, indicating that they might be synonyms of the same species. The morphospecies R. clavigera (Kuster, 1860) singly formed one group, suggesting that it is likely a valid name. The estimated divergence time of the two identified taxa indicates that speciation might have been associated with the sea level and temperature fluctuations during the Plio-Pleistocene period. Our study on Reishia species provides crucial information for further research on the ecology, evolutionary biology, and conservation of this genus.