Population genetics of pike, genus Esox (Actinopterygii, Esocidae), in Northern Italy: evidence for mosaic distribution of native, exotic and introgressed populations

Esox flaviae represents the native esocid species of the Italian peninsula at present potentially highly threatened by the diffusion of exotic E. lucius. Here, we present a novel mtDNA (N = 272) and microsatellite (N = 275) dataset including 13 test and 3 reference samples, aimed to delineate the distribution of the native as well as the exotic species and to unravel potential introgressive hybridisation between the two species in Northern Italy. We highlight a complex mosaic distribution of both species, with contrasting occurrence even between neighbouring sites. Significant genetic substructure is still observed within E. flaviae, while the dispersal of the invader seems to be promoted by restocking actions. In addition, we prove the existence of introgressive hybridisation between native and exotic pikes. Here, gender-biased hybridisation is suggested, with native E. flaviae constituting the predominant ‘mother species’ in the hybridisation process. Finally, we underline the need for a revision of fisheries management regulations, for which a nation-wide and exhaustive genetic screening in the near future should build the scientific basis.