Genetic variation patterns in some groups of Centaurea (Asteraceae) in Italy

In the current work the data of the isozyme analysis of all the twenty studied Italian Centaurea taxa were compared. They belong to Centaurea parlatoris, C. cineraria, C. tenorei and C. jacea groups. The following parameters of the genetic variability were considered: the total number of the alleles, the mean number of alleles per locus (A), the mean percentage of polymorphic loci (P95), the expected heterozygosity (He) that is a measure of the intra-population diversity, the Wright’s fixation index (F) and inbreeding coefficient (FIS) that are measures for the deviation from the Hardy-Weinberg equilibrium. The present study contributes to insight some aspects of the genetic diversity related to the distribution range (endemics or widespread taxa) of the studied Centaurea species. The mean proportion of polymorphic loci and the mean number of alleles per locus (A) in the endemic species are comparable with the widespread ones, while the intra-population diversity (He) results about 40% higher in the populations of the widespread taxa than the endemics. The loci with a major role for the processes of differentiation and evolution of the genus Centaurea in South Italy and Sicily are: Mdh-1, Pgi-2 and Idh-1. Italian Centaurea species with the highest genetic diversity usually inhabit extreme habitats (rocky, sandy places, etc.) and localities with significant human impact or the borderline of their area of distribution. Sicily could be considered a centre of differentiation of the endemic groups of C. cineraria and C. parlatoris which show relatively high intra-population variability.