Genetic Variability of Alnus cordata (Loisel.) Duby Populations and Introgressive Hybridization with A. glutinosa (L.) Gaertn. in Southern Italy: Implication for Conservation and Management of Genetic Resources

Alnus cordata (Loisel.) Duby (Neapolitan alder) is an endemic tree species with a restricted distribution range, limited to Corsica and southern Italy. The economic value of its wood, its rapid growth, the tolerance to drought stress and the nitrogen fixation capacity make A. cordata an excellent candidate for breeding, as well as for conservation and management of genetic resources. In this context, we evaluated the genetic variability of southern Italy populations and verified the hybridization capacity with the simpatric species A. glutinosa (L.) Gaertn. Eight pure A. cordata populations, two pure A. glutinosa populations and six mixed A. cordata/A. glutinosa populations located in southern Italy were analyzed using seven microsatellite markers. A low genetic diversity within and among populations was observed, but no inbreeding effects were evident. A variable frequency of F2 interspecific hybrids was observed in most of the mixed populations and few backcross individuals were scored. These results suggest a limited capacity of hybrid individuals to cross back with the parent species, reducing the risk of genetic pollution of A. cordata. This work provides meaningful knowledge for the conservation and management of the endemic species A. cordata, which represents a valuable source of biodiversity to be conserved.