Non-native and hybrid in a changing environment: conservation perspectives for the last Italian red-legged partridge (Alectoris rufa) population with long natural history

The ever-increasing biotic homogenization - especially when associated with introgressive hybridization - raises concern for the reduction of the spatial component of diversity in wildlife worldwide. Nonetheless, there is a growing attention to the potential conservation value of hybridization in fastening the adaptive evolutionary responses to rapidly changing selective pressures. Under these premises, we investigated the genetic affinity of the red-legged partridge (Alectoris rufa) population inhabiting Elba Island (Italy) in the context of the overall species phylogeography and particularly of the nominate subspecies it is traditionally ascribed to. Although notoriously hybrid with the congeneric A. chukar, this island population is of undisputedly value because of its long natural history and self-sustainability. As such, its adaptive conservation management calls for a comprehensive knowledge including the assessment of its geographic origin. For this purpose, 110 fecal samples were collected across Elba, genotyped at their joint Cytochrome-b and Control Region genes (2,249 characters), and compared with 149 conspecifics from all over the species distribution range. We confirmed a widespread A. chukar mitochondrial DNA introgression in Elba partridges, whereas their expected formal assignment to the nominate subspecies from Italy and France was rejected, since these turned out to be closely related to conspecifics from the Iberian Peninsula. This counterintuitive result found support in a large variety of literary sources and compelling evidences from personal testimonies revealing recent intense management with farm-reared birds of Spanish origin. Although the nativeness of Elba partridges was disproved, we advise local authorities to keep warranting the ongoing conservation efforts - and especially restore the connectivity between the western and eastern island sub-populations - as this resource may still be conceived as the ultimate repository for part of the otherwise extinct Italian A. r. rufa genome. Indeed, the admixture with conspecifics from the Iberian Peninsula does not necessarily mean that the entirety of the native nuclear genome of Elba partridges has been wiped out. Furthermore, these latter represent an interesting case study in conservation biology to investigate the possible role played by introgressive hybridization in the adaptation to recent land use and vegetation cover changes associated with rural abandonment in an insular yet heavily anthropized context.