Conservation genetics of barbel species (Teleostei, Cyprinidae) facing hybridization and introgression along an elevational gradient in protected areas of northern Italy

The European endemic barbels represent important bioindicators of river quality and are nowadays threatened by changing environmental conditions and hybridization with the invasive alien Barbus barbus. It is therefore fundamental to investigate interactions among species and adaptability to climate changes in protected areas of Northern Apennines. An investigation was carried out considering 248 barbel samples that were analysed for Cytb mitochondrial DNA and 192 at 10 microsatellite loci, to delineate the distribution and population structure of the two native species as well as the impact of invasive B. barbus inside 15 sites of the Natura 2000 network. The complex distribution of the native barbel species was highlighted, together with a significant genetic structure emerging in different populations. Only one site revealed a "pure" population of B. caninus while the other ones showed a high level of hybridization between the different barbel species. For the B. plebejus two "genetically pure" populations were found in the hill-mountain sector, while the hybridization level resulted in increasing in the lowest altitudinal stretch of watercourses with a consistent contribution driven by B. barbus. We herein present the first evidence of B. barbus introgression along an altitudinal gradient, carried from the lowland water course to mountain stretches driven by B. plebejus migration. B. plebejus is the species that can act as vicariant organism able to transfer the B. barbus genome from the plain habitats into B. caninus genome of the higher altitude waterstreams, as a consequence of habitat shifts due to climate changes and anthropogenic acitivities.