Molecular markers reveal cryptic species within Polytrichum commune (common hair-cap moss)

Based on morphological characters only, the taxonomy of the moss genus Poly trichum has still not been fully resolved. Application of molecular techniq ues might clarify some of these problems. Within P. commune s.l., the taxon omic status of several varieties, e.g., P. commune var. commune and P. comm une var. uliginosum, is still debated. This study uses allozyme electrophor esis to show that there are two distinct allozyme multi-locus genotypes wit hin our P. commune samples. These two multi-locus genotypes coincide with b oth differences in morphology and differences in habitat association. This division is corroborated by observations from different Danish and Dutch po pulations. Based on these results, in connection with a genetic comparison of the two infraspecific taxa of P. commune s.l. with a related species P. formosum, we argue that P. commune var. commune and P. commune var. uligino sum are two genetically distinct entities with fixed morphological differen ces and a considerable niche differentiation. They should, therefore, be re garded as two distinct species: P. commune and P. uliginosum.