Morphological and molecular diversity among Italian populations of Quercus petraea (Fagaceae)

Quercus petraea is a highly scattered species in Southern and Central Italy. The objective of this work was to evaluate the level of diversity in five Italian populations of Q. petraea and its distribution, by using morphological markers and hypervariable molecular markers such as microsatellites. Forty-eight morphological traits, six nuclear and three plastid loci were scored for each population. Evidence for differentiation in both sets of traits was found, but patterns of differentiation of morphological traits did not coincide with microsatellite differentiation. Morphological variation was correlated with site ecological conditions. Analysis of molecular variance revealed significant genetic variation among populations (P < 0.001) both at the nuclear and plastid levels. Low but significant correlation existed between nuclear genetic distances and geographic distances. The relatively high genetic diversity found in the analysed populations indicates that the maintenance of their evolutionary potential is possible if population sizes are maintained or increased. Low levels of haplotype diversity found within the small southernmost population (Piano Costantino) indicates that genetic erosion may increase the extinction risk for this population.