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Sex-differential resistance and tolerance to florivory in wild strawberry.
Cole, Denise*,1, Bradburn, Megan1, Ashman, Tia-Lynn*,1, 1 University of Pittsburgh, Pittsburgh, PA
ABSTRACT- Sexual dimorphism can modify plant-animal interactions and while there is ample evidence that the sexual morphs of dimorphic plants differ in their attractiveness to mutualists, far less is known about their susceptibility to antagonists (e.g., herbivores). Our understanding of either the traits that bring about herbivore preferences or the potential for sex-differential tolerance to herbivory is still in its infancy. Using gynodioecious wild strawberry (Fragaria virginiana) and one of its major herbivores-the strawberry clipper weevil (Anthonomus signatus), we examined sex-differential susceptibility and tolerance to herbivory. Field surveys of six populations of wild strawberry in Northwestern PA verified that hermaphrodites experience significantly more damage by weevils than females. Data collected from plants grown in a common garden revealed that the probability of attack was influenced by several plant traits, including pollen and flower production. Simulated weevil clipping was a good surrogate for natural weevil clipping and reduced total flower number in both sex morphs. Females were significantly less tolerant than hermaphrodites in terms of fruit and seed number. Hermaphrodites did not compensate fully in terms of flower number but did in terms of fruit and seed production. Clipped hermaphrodites produced significantly more pollen per flower than unclipped plants but this increase was not sufficient to offset flower losses due to herbivory. These results suggest that clipper weevil herbivory results in hermaphrodites whose allocation is shifted towards female function relative to their natural state. This type of herbivore-induced plasticity has consequences for sex ratio and gender evolution.
Key words: sex allocation, tolerance, herbivory, gynodioecy