Microgeographic genetic variation in the haploid and diploid stages of the moss polytrichum juniperinum hedw

Abstract

Electrophoretic variability at six enzyme loci was used to examine genotypic variation in the haploid (gametophyte) and diploid (sporophyte) stages of the moss Polytrichum juniperinum Hedw. from a population in eastern Newfoundland. Samples from 16 sites revealed 13 six-locus haploid genotypes and a total of 18 gametophyte genotypes (ten male and eight female) when the genotypic data were combined with sex. Gametophyte genotypic diversity was low within each site and there was marked microgeographic differentiation between sites within the population. There was, however, no relationship between genetic and microgeographic distances among the sites. The observed number of six-locus genotypes and their relative frequency within the population did not differ significantly from the values expected for a sexually reproducing population. This genotypic structure is consistent with sexual reproduction generating the observed variation but vegatative reproduction and limited dispersal maintaining microgeographic genetic heterogeneity within the population. Diploid, six-locus genotypes were determined for 137 sporophytes. The sporophyte genotypic variation suggested that mating was occurring predominantly between female and male gametophytes within the same site. Fewer gametophyte genotypes were observed than were expected to be produced by sporophyte genotypes observed at each site, suggesting that genetical and/or ecological factors may be limiting the recruitment of new haploid gametophyte genotypes into the population. © 1990 The Genetical Society of Great Britain.