Phylogenetic evidence for multiple and secondary introductions of invasive snails: Pomacea species in the People's Republic of China.
Aim: To determine the genetic diversity of invasive snails (Pomacea spp.) that are implicated in crop damage, environmental degradation and human disease, and to determine their distribution pattern in a large part of eastern Asia. Location: People's Republic of China (P.R. China). Methods: We collected Pomacea snails in a national survey using a grid sampling approach. Overall, 544 snails from 54 sites were used for the present investigation. The mitochondrial cox1 gene was amplified and sequenced from all the snails. We determined and classified the haplotypes using network analyses and mapped them within P.R. China. Haplotypes from this study, together with sequences available from GenBank, were used to reveal the global distribution of Pomacea canaliculata and P. insularum. Results: We obtained 521 cox1 sequences and identified 24 unique haplotypes. Six haplotypes were commonly found in P.R. China. Two species, P. canaliculata and P. insularum, and one cryptic group were observed. The distribution of the 24 haplotypes across P.R. China shows a mosaic pattern. Globally, only six of 112 haplotypes of P. canaliculata, P. insularum, P. dolioides, P. lineata and P. paludosa are shared between introduced and native snail populations. We found 16 haplotype clusters, five of which occur in mainland P.R. China. Three of the five clusters could be traced back to South America. The remaining two clusters were unique to P.R. China. Main conclusions: Phylogenetic analyses indicate that P. canaliculata, P. insularum and two cryptic groups, discovered by the present and previous studies, coexist in the mainland of P.R. China. The mosaic distribution and the high diversity found in the collection sites suggests multiple and secondary introductions. The findings indicate the importance of preventing further intentional introductions and call for appraisal of the risk posed by these snails in vulnerable areas. Discrimination of the ecological impacts of the different species or genotypes will help to develop setting-specific management strategies.