The role of male flowers in andromonoecious species: energetic costs and siring success in Solanum carolinense L.

Two non-mutually exclusive hypotheses regarding the benefits of andromonoecy (producing perfect and female-sterile flowers on the same plant) are tested using Solanum carolinense. Results indicate that (1) staminate flowers are cheaper to produce than perfect flowers, even after correcting for their relative position in the inflorescence; (2) the resources saved by producing staminate flowers are not re-allocated to other fitness enhancing functions; and (3) the main morphological characteristic of staminate flowers, pistil reduction, does not increase either pollinator visitation or siring success of open-pollinated plants. These results indicate that neither the resource savings hypothesis nor the increased pollen donation hypothesis explains the evolution and maintenance of andromonoecy in S. carolinense.