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 among flowering ramets varied from 6% to 40% of females. Female ramets were slightly, although not significantly, taller than males. It appeared that population effects (including both genetic population and environmental site effects) on plant size and allocation patterns at flowering are considerably greater than sex effects. If both flowering and fruit production are considered, then female allocation to reproduction clearly exceeds male allocation. In females, no significant relationship was detected between the mass of reproductive and vegetative tissues, 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. chamaemorus is vegetative propagation, which is the best strategy for reproduction in the unpredictable climate of high latitudes but which leads to skewed sex ratios. As a consequence of vigorous vegetative reproduction, individual clones can grow to be large. The results of electrophoretic studies show that the numbers of clones per population are low.