Genetic Investigations on the Sicilian Populations of Prunus mahaleb L. and Prunus cupaniana Guss ex E. Huet & A. Huet (Rosaceae): Implications for Conservation

Assessing genetic diversity of species and populations can help reduce the risk of biodiversity loss by identifying areas deserving the greatest attention in terms of conservation priority. Our study was focused on evaluating the genetic variability of Prunus mahaleb L. and Prunus cupaniana Guss. ex E. Huet & A. Huet (Rosaceae), both of which are quite rare and unevenly distributed in Sicily (Italy). In this region, P. mahaleb occurs in scattered populations, mostly concentrated on the mountain ranges close to the northern Tyrrhenian coast, while P. cupaniana, which is endemic in Sicily, is known to occur only on Sicani Mountains and on the Madonie Massif. A total of 118 georeferenced individuals of P. mahaleb and P. cupaniana were sampled across eight different sites. The samples were genotyped using nine unlinked nSSr loci. A high percentage of clonal individuals was observed especially in P. cupaniana. Low intrapopulation diversity, as well as high divergence among populations were recorded. The analysis performed using STRUCTURE separated P. mahaleb and P. cupaniana into two different gene pools (K = 2) and revealed the complete absence of introgression between them. These results, if confirmed through further molecular analysis, indicate that these taxa should be considered as two distinct species. Moreover, more detailed analyses allowed us to distinguish four gene pools for P. mahaleb, while the extant populations of P. cupaniana could be grouped into two clusters suggesting their strong isolation and a very low, if any, absent gene flow between them. Our results underline the urgent need for interventions aimed at conserving and managing the genetic heritage of the Sicilian populations of both species.