RESUMO
The role of variable pollination environments in maintaining mixed mating systems is an active area of research. Dimorphic cleistogamy, in which a plant reproduces by both open, facultative outcrossing chasmogamous (CH) flowers and closed, cleistogamous (CL) flowers presents an excellent opportunity to study mixed mating. For example, plastic responses in allocation to an optimal floral type could serve as an adaptive strategy that maintains mixed mating under variable pollination environments. We tested for pollen limitation and plastic responses in allocation to different floral types under manipulated pollination conditions in the dimorphic cleistogamous, mixed mating annual, Triodanis perfoliata. Using a field population, we quantified pollen limitation, auto-fertility and plastic responses in the breeding system by measuring allocation to flower number and seed set of floral types. We found no evidence for pollen limitation for CH flowers, and CH flowers had low efficacy of autonomous selfing. Importantly, we found that T. perfoliata alters floral number following changes in pollination conditions, with pollen-supplemented plants having lower relative CH flower number than non-supplemented plants. Breeding system plasticity may allow for benefits from outcrossing through CH flowers, but also increased overall fitness through relatively cheap CL reproduction. After CH flowers receive pollen, subsequent production of CH flowers was reduced, which may be due to resource limitation. Our findings did not support a theoretical model predicting increased CH flowers with high pollination levels. These results increase our understanding of the role of pollination services and resource allocation in the maintenance of mixed mating systems, which also warrants further investigation.
