Abstract
The green mitten crab, Eriocheir formosa, is endemic to Taiwan. Its sea-ward reproductive migration period occurs between spring and summer unlike that for other species of Eriocheir which migrate during autumn-winter . Therefore, it has high commercial value and is also an important subject for academic studies. The aim of this study was to obtain the molecular marker (mitochondrial cytochrome oxidase I, COI) from E. formosa and to analyse the genetic diversity and population genetic structure for different groups in Taiwan. In the present study, we analysed 602 base-pair fragment of the mitochondrial COI gene from 88 specimens collected from the Northeast to the Southwest of Taiwan. The studied segment of COI sequence is A-T rich (A: 25.9%, T: 35.38%, C: 20.4%, and G: 18.27%)。 The haplotype diversity (h) was found to be 0.73093 with a nucleotide diversity (π) of 0.00185, indicating the population of E. formosa had met a population bottleneck effect and population expansion event. The negative values of Tajima’s D test support the population expansion event. Pairwise Fst values and high gene flow revealed a low level of isolation between populations and molecular dating implied E. formosa first appeared in Taiwan around 7.51~ 2.92 million years ago.