Endangered freshwater limpets in Japan are actually alien invasive species.
Currently, many species are facing the risk of extinction, as it one of the most serious conservation issues. Many conservation programs have evolved to prevent species extinction; however, developing these strategies may prove to be difficult for the species itself, which includes different cryptic species. In this paper, we document the invasion of non-native cryptic species of ancylin limpets, Ferrissia californica, with a molecular phylogenetic analysis. Three species (F. nipponica, F. japonica, Gundlachia japonica) have been described as native, whereas the present analysis shows that most of them are actually non-native F. californica, having been introduced from North America and spreading throughout Japan. In addition, we found a few subpopulations of the cryptic native species of the ancylin limpets, though the native limpet species is very rare, and has limited distribution. The conservation status assigned to ancylin limpets on the Japanese red list is problematic, because F. japonica is listed as an endangered species. All individuals identified as F. japonica are of F. californica, so the current red list treats invasive non-native species as endangered. Reassessment of the conservation status of native species and an estimation of the impact of non-native species is required to better delineate these limpet species by genetic markers.