Molecular characterization of a hybrid zone between Orchis mascula and O-pauciflora in Southern Italy

A small population (16 individuals) of Orchis x colemanii Cortesi, a natura l hybrid between O. mascula (L.) L, and O. pauciflora Ten. was sampled from a locality near Sassano (National Park of Cilento, province of Salerno, So uthern Italy) in order to assess its genetic structure. Filter hybridizatio ns of O. x colemanii, O. mascula and O. pauciflora DNAs against a PCR-ampli fied ribosomal fragment indicated that all the hybrid individuals in study have the ribosomal repeats of both parents, even if not always combined in equal proportions, and that no specimen morphologically identified as O. ma scula or O. pauciflora possessed detectable rDNA of the other species. The majority of the hybrid specimens (12 individuals) showed a preponderance of O. mascula rDNA, three had approximately equal proportions of parental rep eats and one had a preponderance of O. pauciflora rDNA. As the parental spe cies have different amounts of rDNA, as inferred from dot blot hybridizatio n, it has been deduced that the 12 specimens may represent F-1 or successiv e, presumably non-recombinant progenies, while the last four specimens may represent either F-2 genotypes or backcrosses with O. pauciflora.