| Mitten crabs of the genus Eriocheir are economically important species endemic to East Asia.; The present study examined the genetic differentiation and phylogenetic relationships among populations of Eriocheir s. s. throughout its geographical range, using partial sequences of mitochondrial cytochrome c oxidase I (COI) and cytochrome b (Cyt b) genes, restriction fragment length polymorphism (RFLP) of Cyt b fragment, and amplified fragment length polymorphism (AFLP), in order to clarify the evolutionary history and evaluate the taxonomy of these crabs. The genetic variability of the native and introduced populations of E. sinensis and the relationships between them were also investigated using sequences of mitochondrial DNA (mtDNA), microsatellites and AFLP. The possible history and pathways of introduction were reconstructed.; The results from mtDNA analyses show that Eriocheir s. s. consists of four distinct clades, with sequence divergence >2.6% between clades and <0.5% within clades. Most E. sinensis cluster into one clade, distributed in rivers along the Yellow Sea and East China Sea, and E. japonica is generally separated into three clades, namely Japan, Okinawa and China clades, inhabiting areas around the Sea of Japan, Okinawa islands, and rivers along the East China Sea and South China Sea, respectively.; AFLP analyses separate all the individuals into two clades, representing E. japonica and E. sinensis respectively. Similar to mtDNA analyses, most E. sinensis cluster into one clade, and E. hepuensis do not form a group itself but cluster with E. japonica, indicating that it should not be considered as a separate species or subspecies. The three mtDNA clades of E. japonica constitute a single clade in AFLP analyses, with the Okinawa and Japan clades being closely related and differentiated from the China clade. The sympatric zone in southeast China identified by mtDNA was demonstrated to be a hybrid zone of E. japonica and E. sinensis. Analysis of limited number of specimens from Vladivostok shows that this is also a hybrid zone of the two species, but hybridization in this region is likely to be a historical event, with the absence of E. sinensis at present. Considering the morphological and genetic distinctness of the two taxa, in extensive areas outside the hybrid zones, both E. japonica and E. sinensis are regarded as valid species. (Abstract shortened by UMI.)... |
