Amount and structure of intra- and interspecific genetic variation in the moss genus Polytrichum

Allozyme electrophoresis was used to determine amount and structure of gene tic variation within and between five congeneric haploid moss species: Poly trichum formosum, P. commune, P. uliginosum, P. piliferum and P. juniperinu m. For the different species, gene diversity within populations (H-S) range d from very low (0.025) to moderate values (0.127), being, on average, lowe r than those observed for vascular plants and many other moss species. Poly trichum piliferum and P. juniperinum showed significantly higher levels of H-S than the other species examined, which possibly might be explained by s exual reproduction being more prevalent in these two species, that often li ve in more dynamic habitats, where turnover of individuals is more frequent . Genetic variability was observed to be structured in contrasting ways at different levels. At the intraspecific level genetic differentiation among populations of most Polytrichum species was low, F-ST less than or equal to 0.1, indicating a considerable degree of gene flow by wind-dispersed spore s over substantial distances. At the interspecific level strong divergence, genetic identities being on average I=0.222, was observed between most spe cies studied, despite low levels of divergence at the morphological level. These I-values are significantly lower than observed for congeneric vascula r plant species and most congeneric bryophyte species. This suggests that t he morphological conservatism is not due to lack of genetic variability and evolutionary potential.