Contributo alla revisione dei caratteri diagnostici nel gruppo Viola alba W. Besser: analisi morfologica e cariologica delle popolazioni dei Monti della Tolfa

Revision of diagnostic characters in Viola alba complex: morphological and kariological analysis in Tolfa Mts. population.- The species of the Viola alba Besser complex exhibit a high variability at regional, local and individual scale, that, alongside with the frequent hybridization with taxon outside the complex, has led to the description of a lot of new species and subspecies and their relative distribution areas. At present, many authors prefer to consider V. alba a single species with an elevated morphological variability. In this study, the exact distribution of the V. alba populations has been accomplished in the territories of the “Monti della Tolfa” and “Lazio” region (central Italy). By means of biosystematic analysis (histological, morphometric and karyological) we have evaluated the phenotypic plasticity, the reliability of diagnostic traits and have defined the subspecific taxa really occurring in the investigated area. Voucher samples were prepared and compared with Herbarium specimens of RO, NAP, FI to evaluate intra and inter- populations variability. Cultivated samples have showed that diagnostic characters may be variable at different phenological phases and at different developmental steps, suggesting a their revaluation. Karyological analysis have suggested that populations of Tolfa mountains are resembling more to subsp. dehnhardtii on the basis of Levan formula, but are intermediate between the typus alba and dehnhardtii according to the cromosomal sizes and shapes. Therefore, it appear to be correct to partition V. alba Bess. in three subspecies: alba, dehnhardtii and cretica, each of them deriving from 3 different glacial refugial areas.