Beam Brook revisited: a molecular study of a historically introduced non-native amphibian (Triturus carnifex) and its limited introgression into native UK Triturus cristatus populations

Human mediated introductions of non-native species can pose a major threat to global biodiversity on several accounts i.e. through competition, the introduction of novel pathogens, and genetic pollution. Where hybridization occurs between two closely related species the F1 offspring are usually phenotypically discernible whereas F2 hybrid, backcrossed or admixed individuals become more difficult to separate. At this point the utilization of molecular methods is required in conservation efforts to differentiate and manage populations. This study demonstrated how a possible threat of hybridization from an introduced non-native (T. carnifex) with a protected native newt species (T. cristatus) could be investigated with molecular tools, and examined the current extent of its genetic introgression over an 80 years period. The results confirmed that hybridization had taken place at the site of introduction (and continues to do so), and that historically limited local dispersal of both non-natives and/or hybrids had occurred sometime in the past. However, the data suggests that although dispersal of hybrids into a local satellite site may still be occuring, hybridization with native species appears limited.