SEX-RATIOS AND RESOURCE-ALLOCATION AMONG SEXUALLY REPRODUCING PLANTS OF RUBUS-CHAMAEMORUS

Sex ratios and patterns of size variation and resource allocation were investigated in the dioecious species Rubus chamaemorus. Sex ratios a mong flowering ramets varied from 6% to 40% of females. Female ramets were slightly, although not significantly, taller than males. It appea red that population effects (including both genetic population and env ironmental site effects) on plant size and allocation patterns at flow ering are considerably greater than sex effects. If both flowering and fruit production are considered, then female allocation to reproducti on clearly exceeds male allocation. In females, no significant relatio nship was detected between the mass of reproductive and vegetative tis sues, while males did exhibit such a relationship. Reproductive effort was less for tall males than for small males. Despite the occurrence of sexual reproduction, the main mode of reproduction in R. chamaemoru s is vegetative propagation, which is the best strategy for reproducti on in the unpredictable climate of high latitudes but which leads to s kewed sex ratios. As a consequence of vigorous vegetative reproduction , individual clones can grow to be large. The results of electrophoret ic studies show that the numbers of clones per population are low.