Molecular diversity patterns and introgression in alpine and Northern European populations of Arctic charr (Salvelinus alpinus)

The origin of Arctic charr populations in the lakes of the Italian Alps is not well understood. While some studies have suggested that they are postglacial relics, others have proposed that these populations are the result of intentional stocking efforts dating back to the sixteenth century. Subsequent introductions of Arctic charr to these lakes have made it difficult to untangle the evolutionary history of these Alpine populations. In this study, we examined the distribution of genetic variation among Arctic charr collected throughout their Northern and Southern European ranges at the beginning of the twenty-first century, using nuclear (amplified fragment length polymorphisms) and mitochondrial (control region and cytochrome oxidase I) loci. These analyses revealed the impact of restocking activities, which have resulted in admixture and hybridisation with Brook charr (Salvelinus fontinalis) in Italian alpine lakes and provides clues on the native or pseudo-native origin of Trentino-Alto Adige populations. The lack of detailed historical information, however, makes it difficult to disentangle the postglacial history of the species and to determine how much of the current diversity pattern can be ascribed to the consequences of Pleistocene events or anthropogenic activities.