Genetic structure in relation to reproductive biology of 11 species of Pohlia Hedw. (Bryaceae)
The moss genus Pohlia includes species with bisexual gametophytes, unisexual gametophytes and no specialized asexual propagules, and unisexual with specialized asexual 'gemmae.' A group of Northern Hemisphere species characterized by having axillary gemmae are very similar in other gametophytic characters, and virtually identical in sporophyte morphology, in contrast to most other species of Pohlia that differ in both gametophytic and sporophytic features. This study tested the hypothesis that gemmiferous taxa form a complex of 'microspecies' that are less distinct genetically than are comparable sexual species. Fourteen putative isozyme loci were screened in 50 populations representing 11 species (7 gemmiferous and 4 nongemmiferous). The seven gemmiferous species are less distinct from one another (mean I = 0.8999) than are the four species that do not form gemmae (mean I = 0.7530). Species lacking gemmae have higher total infraspecific gene diversity (mean H(T) = 0.254) than gemmiferous species (mean H(T) = 0.138).