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Vegetative herbivory affects the mating system of Impatiens capensis.
Steets, Janette*,1, Ashman, Tia-Lynn1, 1 Department of Biological Sciences, Pittsburgh, PA
ABSTRACT- Vegetative herbivory can affect plant mating system directly, by lowering plant resources, or indirectly, by influencing pollinator visitation to damaged plants. Using multiple experimental approaches, we analyzed the mechanisms by which vegetative herbivory affects the mating system of Impatiens capensis, a species with an environmentally-determined mixed-mating system (producing both cleistogamous, obligately selfing flowers, and chasmogamous, facultatively outcrossing flowers). We found that herbivory affected the expression of mating system directly by increasing the proportion of flowers and seeds that were cleistogamous and by altering the relative quality of cleistogamous and chasmogamous progeny. The overall direct effect of herbivory on mating system was to increase the proportion of fitness achieved through cleistogamous progeny. In addition, vegetative herbivory affected characteristics associated with the mating system including chasmogamous floral display size and floral attraction traits, resulting in a decrease in pollinator visitation to damaged plants. The significant decreases in flower number, flower shape, and pollinator visitation, may lead to changes in the outcrossing rate of chasmogamous flowers. Our findings are among the first to demonstrate that vegetative herbivory has direct consequences on plant mating system and should be considered a factor shaping mating system evolution.
Key words: herbivory, Impatiens capensis, plant-pollinator interactions, outcrossing