Sexually dimorphic growth in the dioecious tropical shrub, Siparuna grandiflora

1. To demonstrate evolved sex-based differences in vegetative traits of dio ecious plant species, one must consider both pre-reproductive and reproduct ive individuals, as dimorphic patterns commonly arise secondarily from diff erent effects of reproduction on resource balance. 2. Siparuna grandiflora, a neotropical dioecious shrub in which females all ocate significantly more biomass to reproduction than males, was studied fo r 2 years (three reproductive events) to determine whether sex-based differ ences in stem growth, leaf production and allocation pattern could be detec ted in pre-reproductive individuals grown from cuttings in field plots or i n mature naturally occurring individuals. 3. Among pre-reproductive individuals, females accumulated more stem and le aves than males, but among mature individuals, no sex-based growth differen ces were apparent. In mature individuals, both growth and leaf longevity we re positively correlated with reproductive frequency. With regards allocati on, pre-reproductive males had larger leaves than females, and mature femal es allocated less biomass per unit stem length than males. 4. The capacity of pre-reproductive females to grow faster than males demon strates innate differences between the sexes. That mature females achieved equivalent growth to males, despite higher reproductive allocation, indicat es that the greater growth capacity of young females is sustained in older females and enables them to compensate for greater reproductive allocation.