XVI International Botanical Congess

One hypothesis for the wide diversity of breeding systems in angiosperms is offered by sex allocation theory. This theory assumes that a shift in allocation of resources to stamens increases male fitness and decreases female fitness. The shapes of such fitness gain functions then determine whether hermaphroditism is evolutionarily stable. This study used paternity analysis to estimate the fitness gain functions and test the ability of the model to explain the level of biomass allocation to stamens in a hermaphroditic herb. As predicted, the male gain curve showed diminishing returns. However, observed allocation to stamens was higher than expected from the fitness gains. One explanation for this discrepancy is the lack of negative genetic correlations between biomass of stamens, pistil, and seeds. In concluding the talk I will offer ideas for more powerful tests of sex allocation theory.