Allozymic variability in Centaurea tenorei Guss. ex Lacaita and in other species of C. parlatoris Heldr. group (Asteraceae)

ABSTRACT

The genetic diversity in Centaurea tenorei Guss. ex Lacaita, an endemic species of the “Penisola Sorrentina” (Campania region, Italy), was assessed by comparing the allozymic polymorphisms of its populations, hitherto considered as different formae of this taxon. These forms are discontinuously distributed along the coasts (C. tenorei fo. maritima) and on the internal reliefs (fo. tenorei and fo. montaltensis). Based on unpublished data, C. tenorei fo. tenorei is diploid while the others are tetraploid. In order to compare C. tenorei with the Italian congeneric, strictly related species, this analysis was extended to at least one population of all the other species enclosed in the C. parlatoris Heldr. group, in particular C. parlatoris, C. scannensis and C. ambigua, all known to be diploid. Our results point to a very low genetic diversity (He=0.08; 0.14) in fo. tenorei and fo. montaltensis, while fo. maritima (He=0.26) exhibits levels of allozymic variability similar to those observed in the other populations examined. Moreover, Wright's F statistics suggest a high inbreeding level (F_is=0.42) and a low genetic flow (F_st=0.34) among C. tenorei populations. We propose that the differences among the three forms of C. tenorei may depend upon their population size, mating system and different ploidy level. However, since they fail to form a unique group in the cluster analysis, it is suggested that a probable reticulate evolution obscures the relationships among the examined taxa, which, in any case, started to diverge only in recent times.