Clonal structure and genet-level sex ratios suggest different roles of vegetative and sexual reproduction in the clonal moss Hylocomium splendens

The allozyme haplotype was determined for 157 ramets of the unisexual, perennial, clonal moss Hylocomium splendens within five 10×10 cm plots, which had been the subject of demographic studies over a 5-yr period. In addition, 25 shoots were analyzed from outside the plots and from four neighbouring patches. Only four haplotypes were encountered within the plots; one female type occurred in all plots and one male type in four plots, whereas two male haplotypes occurred in only one plot. Genets grew intermingled in all but one plot. The sex ratio within the five plots was female-biased at the ramet level (male:female=1:2.6), but male-biased at the genet level (3:1). Sporophytes were produced abundantly during the study period, but no signs of recruitment from spores were observed in the plots. Nine additional genets were encountered in neighbouring patches but from only one patch each. Four (44%) of these could potentially have been derived from spores generated within the plots. Our results suggest that each patch of H. splendens is colonized by a small number of genets, whereas different patches have different sets of genets, i.e. clonal diversity is determined by vegetative reproduction at within-patch scales and structured by sexual processes at among-patch scales.