The origin of invasion of an alien frog species in Tibet, China

Identifying the origins of alien species has important implications for effectively controlling the spread of alien species. The black-spotted frog Pelophylax nigromaculatus, originally from East Asia, has become an alien species on the Tibetan Plateau (TP). In this study, we collected 300 individuals of P. nigromaculatus from 13 native regions and 2 invasive regions (including Nyingchi and Lhasa) on the TP. To identify the source region of the TP introductions, we sequenced portions of the mitochondrial cyt b gene. We sequenced a similar to 600-bp portion of the mitochondrial cyt b gene to identify 69 haplotypes (124 polymorphic sites) in all sampled populations. According to the network results, we suggest that the P. nigromaculatus found on the TP was most likely originated from Chongqing by human introduction. Furthermore, we found that the genetic diversity was significantly lower for invasive than for native sites due to founder effects. Our study provides genetic evidence that this alien species invaded the cold environment of high elevations and expanded the distribution of P. nigromaculatus in China.