Genetic variation in Orchis papilionacea (Orchidaceae) from the Central Mediterranean region: taxonomic inferences at the intraspecific level

The genetic differentiation of Orchis papilionacea from Italy, Corsica, Sardinia, Sicily, and Greece was analyzed by isozyme studies. No significant differences at any of the 28 loci tested were observed between samples of the putative subspecies papilionacea from Italy, grandiflora from Sicily and heroica from Greece, or by comparing sympatric papilionacea-like and grandiflora-like subsamples from Sardinia and Corsica. The genetic relationships found among the populations studied reflect more their geographic origin than their taxonomic assignment; papilionacea, grandiflora, and heroica are, therefore, at least in the study area, not to be considered as subspecies, but as simple morphs, controlled by few genes (possibly two) with Mendelian inheritance. The genetic divergence observed among the samples studied is very low and consistent with that of geographic populations of a single cohesive gene pool, linked by a high gene flow (Nm = 5.9).