Extending the natural range of a declining species : Genetic evidence that great crested newt (Triturus cristatus) populations in the Scottish highlands are native

Determining whether isolated populations of a species are native or introduced is important for conservation, as non-native occurrences are likely to be of lower priority for conservation organisations with limited resources. The great crested newt Triturus cristatus is an important wetland flagship species in the UK, and recent evidence suggested that putatively introduced isolated occurrences around Inverness (Scottish Highlands) might be of native origin. Here, we use six microsatellite loci and mtDNA sequence information (ND4 region) to genetically characterise eight Highland populations, comparing them with two populations from central Scotland (the northern limit of the species’ continuous UK distribution) and central England (Leicestershire). Highland populations were characterised by low amounts of genetic variation at high degrees of differentiation, which can be best interpreted by demographic instability and isolation at the periphery of the species’ range. We found no evidence for population bottlenecks in the last decades. All studied individuals possessed a single mtDNA haplotype previously described for British T. cristatus. Taken together, these results suggest that T. cristatus is native to the Scottish Highlands, with important implications for its local conservation status