XU, Jiawu; CHAN, Tin-Yam; CHU, Ka Hou; The Chinese University of Hong Kong; National Taiwan Ocean University; The Chinese University of Hong Kong: Population aggregation analysis of mitten crabs in Eriocheir, sensu stricto, based on mitochondrial DNA

The taxonomy of mitten crabs (Eriocheir) native to East Asia has been problematic and controversial. In the most recent taxonomic revision of the mitten crabs, Eriocheir, sensu stricto, is regarded to comprise the species E. japonica, E. sinensis, and E. hepuensis, but this classification scheme has not been widely accepted by other taxonomists. The present study analysed the genetic differences among populations of Eriocheir s.s. throughout most of its geographical range using mitochondrial cytochrome b and cytochrome c oxidase I gene sequences. The results show that E. hepuensis is not genetically distinct from E. japonica in mainland China and Taiwan and thus should not be considered a separate species. Phylogenetic analysis indicates that E. japonica (including E. hepuensis) in the above region is more closely related to E. japonica in Okinawa than to E. japonica in Japan, or E. sinensis. The genetic divergences among geographical populations of E. japonica are high (3-5%), while those among E. sinensis populations are much lower (<0.5%). In almost all analyses, E. japonica populations constitute a paraphyletic assemblage so that its species status as currently defined to include crabs from outside Japan is debatable. To conclude, this study provides new data on Eriocheir taxonomy and demonstrates that further investigations preferably using nuclear DNA markers are needed to resolve this controversy.