Phylogeography of Italian barbels (Cyprinidae, Barbus) inferred by mitochondrial and nuclear markers.

Species of the genus Barbus, being primary freshwater fishes intolerant of salt water, are of great value for biogeographic studies since their dispersal strictly depends on geological evolution of the landmasses (i.e. catchments watershed, mountain chains and fluctuations of sea level). In Italian peninsula four specie are formally recognized: B. caninus, B. balcanicus, B. plebejus and B. tyberinus. Their genetic relationships were assessed using both mitochondrial and nuclear markers. The study was carried out as first developing new nuclear primers for the S7 ribosomal protein and the Growth hormone genes (Gh); then performing a SNPs characterization of these loci on 18 populations (264 specimens in total). Results from nuclear sequences were then compared with those from partial sequences of the Cytochrome b mitochondrial gene (733 bp). Recovered phylogenies were congruent with the current morphology-based systematic and taxonomy. Results highlighted the close relationships between species belonging to the fluvio-lacustrine ecological group: B. plebejus and B. tyberinus and the high genetic distance between species belonging to the riverine group: B. caninus and B. balcanicus. Moreover findings were congruent with hypotheses of partial permeability of principal biogeographic barriers (Alpine and the Apennine chains) to freshwater fish fauna. Successively the influence of different ecological preferences on gene flow was tested for B. caninus and B. tyberinus on 6 and 7 populations respectively. Results pointed out that the riverine B. caninus has higher structured populations than B. tyberinus, probably due to the different dispersion ability and the different habitat colonized. Moreover, for the first time, molecular evidences were shown about hybridization events occurring between B. caninus and B. plebejus, B. tyberinus and B. barbus.