GENETIC-VARIATION IN THE CLONAL BRYOPHYTE HYLOCOMIUM SPLENDENS AT HIERARCHICAL GEOGRAPHICAL SCALES IN SCANDINAVIA

The widespread bryophyte Hylocomium splendens was sampled in a hierarc hical fashion from populations representing four Scandinavian vegetati on zones. Allozyme electrophoresis revealed variation at 11 out of 13 screened loci, allowing accurate identification of genotypes. From a t otal sample of 298 shoots 79 genotypes could be detected, giving the p roportion of distinguishable genotypes (PD) of 0.265. The total alleli c diversity (H-T) based on polymorphic loci was 0.274. The relative di fferentiation among populations was low (G(ST) = 0.073), indicating a high level of gene flow. Differences in population structuring occurre d between a subarctic-alpine site vs. three lowland sites. The subarct ic-alpine population had one widespread clone, which appeared to be pr opagated by dispersal of vegetative fragments. That population also co mprised many rare genotypes, often occurring together within 10 x 10 c m patches. The lowland populations had genotypes that were locally com mon and often dominant within the patches. When identical genotypes we re observed in multiple patches within these populations, it was usual ly statistically highly probable that they had arisen by independent s exual recombinations.