The genetic diversity of seven taxa endemic to Sicily, C. cineraria, C. busambarensis, C. ucriae subsp. ucriae, C. ucriae subsp. umbrosa, C. todari, C. erycina and C. saccensis, from 11 localities was investigated using isozymes. Eight loci from five enzyme systems (IDH, MDH, PGD, PGM and PGI) were examined. A total of 19 alleles were identified, some rare and two of them exclusive to different populations. The allelic frequencies and the genetic variability values for each population were calculated. On the whole, the genetic diversity, i.e., average polymorphism (P) = 0.41, average number of alleles per locus (A) = 1.75, Nei's gene diversity (H) = 0.18, is moderate, with the highest genetic variability found in the populations of C. todari. The dendrogram shows two major groups: the first consists of all Sicilian populations except those of C. todari; the second of C. cineraria from the region of Campania and C. todari.

13 p.[EN] Section Cyanus of Centaurea is a group that is very well defined morphologically and, thus, is a good\ud representative of many radiations of eastern groups of the genus in the Mediterranean region. To confirm the\ud existence of the two natural groups, subsect. Cyanus (annual species) and subsect. Perennes (perennial taxa),\ud typically defined within this section, and to confirm their radiation patterns, a molecular phylogenetic analysis\ud was carried out using the highly variable nuclear-ribosomal spacers ITS (internal transcribed spacer) and 39ETS\ud (external transcribed spacer). Our results confirm the eastern origin of the group, which probably arose from\ud a Caucasian and North Iranian stock. Both subsections are monophyletic, and annuals (subsect. Cyanus) arose\ud from perennials in Anatolia. The radiations of the two subsections follow very different patterns. Inconsistencies\ud between present classifications and molecular results strongly suggest that the present delineation of some species\ud (Centaurea triumfetti being the best example) is incorrect, and a deep taxonomic revision is necessary.Peer reviewe