1999 Volume 86 Pages 121-135
We used starch-gel electrophoresis to examine levels of genetic diversity at 12 enzyme loci in 21 populations of P. piliferum from five geographical regions in North America and Europe. Mean levels of genetic diversity were very low (Hs = 0.037) compared to most other mosses, averaging about half the levels we observed in other species of Polytrichum. Low genetic diversity and high genetic identity between populations made it difficult to identify any genetic structure on a large geographical scale. The only genetically distinct subgroup was a cluster comprised of four populations from the Pacific Northwest with the one population from Europe. Of the total genetic diversity, 72% was expressed as differences among populations, suggesting that gene flow via spores or asexual propagules is limited. Genetic diversity within the single population of a related taxon, P. hyperboreum, was very high (Hs = 0.203). The low genetic identity (I= 0.707) between P. piliferum and P. hyperboreum supports their recognition as distinct species.