Predispersal seed predation determines the opportunity for selection and female fitness gain curves in an andromonoecious herb
ID: 613 / 288
Proposed Symposium Title: Predispersal seed predation determines the opportunity for selection and female fitness gain curves in an andromonoecious herb
Kai-Hsiu Chen and John R. Pannell
Affiliations: University of Lausanne, Department of Ecology and Evolution, Lausanne, Switzerland
Backgrounds: Predispersal seed predation is an antagonistic plant-animal interaction with potentially major implications for plant fitness and selection on flowers, but it is much less well studied and understood than mutualistic interactions such as those involving animal pollinators.
Methods: In this talk, I will report on the selective effects of seed predation by a specialist fly, Phytomyza sp. on pistil number within flowers of the andromonoecious alpine herb, Pulsatilla alpina, drawing on trait and fitness measures taken across multiple populations and years in the Swiss Alps.
Results: Seed predation decreased the mean and increased the variance in female reproductive success, quantified as the mature seed number. In all populations studied, seed predation rate depended positively on within-flower pistil number, causing saturation of the fitness return on resource allocation to female function, with the degree of saturation increasing steeply with the intensity of seed predation. Antagonistic interactions thus contribute towards stabilizing the hermaphroditic sex-allocation strategy of P. alpina.
Conclusion: Our study demonstrates the potential importance of antagonistic interactions between flowers and animals in molding selection on floral traits and plant sexual systems. It also exposes a novel mechanism for the saturation of sex-allocation fitness-gain curves at the flower level, something that may be common in other species influenced by antagonistic interactions. I will discuss how our findings help to explain the evolution and maintenance of andromonoecy.