Genetic and phenotypic displacement of an endemicBarbuscomplex by invasive European barbelBarbus barbusin central Italy

Invasions of alien fishes can result in considerable consequences for native biodiversity, including local extinctions of native species through genetic introgression. In Italy, the alien European barbelBarbus barbuswas first detected in 1994. It has since undergone range expansion, raising conservation concerns on their impacts on endemicBarbusspecies, includingBarbus plebejusandBarbus tyberinus. Here, the genetic and phenotypic consequences ofB. barbusinvasion in the Tyrrhenian and Adriatic basins of central Italy were assessed by comparing 'invaded' with 'uninvaded' river sections that remain free ofB. barbusdue to barriers preventing their upstream dispersal. In both basins, uninvaded sites were confirmed asB. barbusfree, but the endemic populations had low genetic variability. In the invaded sections, haplotype and nucleotide diversity was relatively high, with introgression skewed towardsB. barbusgenes, with the barbel populations comprising of only 4% and 23% of pureB. tyberinusandB. plebejusrespectively. Relatively high morphological differentiation was apparent between pureB. tyberinusand hybrid forms, whilst differences were less apparent between pureB. plebejusand their hybrid forms. Thus, the endemicBarbusspecies only persist in areas that remain free of invasiveB. barbus, with this only due to river structures that impede their upstream movements. As these structures also limit the effective population size of the endemic species, conservation plans must reconcileB. barbusdispersal prevention with the need to increase the population connectivity of the endemics.

Automated summary

The genetic and phenotypic consequences of European barbel invasion in central Italy were assessed. Uninvaded sites were found to have low genetic variability, while invaded sections showed relatively high haplotype and nucleotide diversity, with introgression skewed towards European barbel genes.