The evolution of hermaphroditism : An experimental test of the resource model.

Most plants are hermaphrodite (cosexual). Charnov et al. (1976) advanced the hypothesis that cosexuality is favoured in plants because a convex fitness set is generated by a non-additive relationship between male and female resource costs. In the first experimental test of this hypothesis, reproductive costs were measured in a male x female factorial design using male, female, cosexual, and neuter cucumber plants. Costs were measured by plant's vegetative growth response to treatments. The results show that male costs in the system used have negligible effect upon plant growth and female function, and imply a convex fitness set, in accordance with Charnov et al.'s model. Female function (fruit set) has an inhibitory effect upon vegetative growth and male flower production, favouring protandry.