Geographic distribution of chloroplast variation in Italian populations of beech (Fagus sylvatica L.).

The distribution of chloroplast DNA (cpDNA) variation in Italian beech (Fagus sylvatica L.) populations was studied using PCR-RFLP and microsatellite markers. In total, 67 populations were analysed, and 14 haplotypes were identified by combining the two marker types. A remarkable subdivision of cpDNA diversity in Italian beech was found, as indicated by a high level of genetic differentiation (Gst=0.855). The highest level of total haplotype diversity (ht=0.822) was estimated for southern Italian populations. The highest number of haplotypes was found in the central-southern region of the peninsula. The nested clade analysis provided evidence for past fragmentation events that may have been occurred during the Quaternary glaciations and had a major role in defining the genetic structure of the central-southern Italian beech populations. Only one haplotype apparently spread towards the north of Italy along the Apennine chain and reached the Italian slope of the western part of the Alps (Maritime Alps, Liguria). All haplotypes found along the Apennines remained trapped in the Italian peninsula. Southern and central Italy represent hotspots of haplotype diversity for Italian beech.