RAPD markers for genetic differentiation of species within Polytrichum (Polytrichaceae, Musci): a preliminary survey

A combination of morphological data and RAPD markers were analysed using th irty colonies from Brittany (France) in six taxa of Polytrichum: P. commune , P. c. var. perigoniale, P. formosum, P. juniperinum, P. piliferum, and P. strictum. Ten primers selected for the RAPD study produced 166 polymorphic markers useful for cluster analysis. The Jaccard index of similarity was h igh within and among taxa and varied from 0.56 between P. commune and P. fo rmosum to 0.89 between P. formosum and P. juniperinum. For the morphologica l study, shape of terminal cells of the green lamellae covering the upper s urface of leaves allowed differentiation of taxa. In P. commune var, perigo niale these cells were narrower and less deeply notched than in P. commune. The diameter of leaves was scored for many individuals of the six taxa and revealed a sexual dimorphism for size. Female plants have a significantly larger leaf rosette diameter than male plants. Morphological results are la rgely consistent with RAPD data. However, the high level of genetic differe nces of P. c. var, perigoniale and P. strictum with other taxa demonstrates the potential of molecular and genetic data in phylogenetic analysis among closely related taxa. The cluster analysis divides the taxa into two group s: (I) P. commune, P. formosum and P. c. var. perigoniale; and (2) P. junip erinum, P. piliferum, and P. strictum. The results do not support splitting the genus into Polytrichum and Polytrichastrum nor the possibility of hybr id origin of P. c. var, perigoniale between P. commune and P. formosum.