Flower morphology and pollinator dynamics in Solanum carolinense (Solanaceae): implications for the evolution of...

Flower morphology and pollinator dynamics play an important role in the evolution and maintenance of many breeding systems, including andromonoecy. We used a series of field experiments to test the functional relationship between flower morphology and pollination dynamics (e.g., pollen receipt and export) in Solanum carolinense. We find that long-styled flowers serve primarily as pollen recipients and short-styled flowers as pollen donors, making this the first study to support the male-female interference hypothesis for the evolution of andromonoecy. However, this difference in the primary male or female function of the flowers depends on the pollinator identity. In flowers visited by Bombus impatiens, style length has a positive relationship with pollen deposition and a negative relationship with pollen removal. In contrast, neither morphological nor behavioral traits determine pollen deposition or removal by small halictid bees. We demonstrate that different pollinators could select for different floral morphologies, and thus, our research suggests that pollinator-specific interactions with flower morphology play an important role in the evolution and maintenance of anrdromonoecy.