Reproductive allometry describes the extent to which individuals of different sizes translate vegetative biomass into reproductive biomass. Life history theory predicts that sexually dimorphic species, such as dioecious, trioecious, gynodioecious or androdioecious plants, should show different reproductive allocation. However, studies of reproductive allometry in sexually dimorphic species are scarce, despite that different genders often differ in size and thus direct comparisons of reproductive allocation can be misleading. Sexual differences have been found for traits related to resource acquisition and allocation, as well as in flower size, flower number per inflorescence, total floral display, and inflorescence architecture. These differences could potentially lead to sexual dimorphism in reproductive allometry. Following predictions of life history theory, one would expect male plants to show higher slopes or intercepts of the allometric relationship at flowering than female plants. The opposite should be true at fruiting.
Results/Conclusions
I reviewed the literature on reproductive allometry and found 13 studies dealing with sexually dimorphic (dioecious, subdioecious, and gynodioecious) species. I added information for five species. In some dioecious species, higher slopes or intercepts of the male reproductive allometry were found, compared to the female one. In one gynodioecious species, higher slopes were found for the hermaphroditic reproductive allometry, compared to the female one. In a substantial percentage of cases, though, no differences in reproductive allometry were found among genders. Current evidence is consistent with predictions of life history theory but a broader data set needs to be gathered in order to allow tests of differences between different breeding systems, and between woody and herbaceous plants.
