Zouhair, R., Corradini, P., Defontaine A. & Hallet, J. N.: RAPD markers for genetic differentiation of species within Polytrichum(Polytrichaceae, Musci): a preliminary survey – Taxon 49: 217–229. 2000. – ISSN 0040‐0262. A combination of morphological data and RAPD markers were analysed using thirty 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 high within and among taxa and varied from 0.56 between P. communeand P. formosumto 0.89 between P. formosumand P. juniperinum.For the morphological study, shape of terminal cells of the green lamellae covering the upper surface of leaves allowed differentiation of taxa. In P. communevar. perigonialethese 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 largely consistent with RAPD data. However, the high level of genetic differences of P. c.var. perigonialeand P. strictumwith 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 groups: (1) P. commune, P. formosumand P. c.var. perigoniale;and (2) P. juniperinum, P. piliferum,and P. strictum.The results do not support splitting the genus into Polytrichumand Polytrichastrumnor the possibility of hybrid origin of P. c. var. perigonialebetween P. communeand P. formosum.