Plants of scarlet gilia, Ipomopsis aggregata, are exposed to high levels of mammalian herbivory (by mule deer, Odocoileus hemionus, and elk, Cervus elaphus) early in the season, before flowering. During the period of this study, up to 56% of all individuals experienced a 95% reduction in aboveground biomass. Browsed plants rapidly responded by producing new inflorescences and flowering within 3 weeks. Unbrowsed plants produced only single inflorescences, whereas browsed plants produced multiple inflorescences. Field observations and experimental manipulations showed that plants with multiple inflorescences produced significantly greater numbers of flowers and fruits than unbrowsed individuals. There was no difference in between browsed and unbrowsed individuals in the number of seeds produced per fruit, seed weight, subsequent germination success, and survival. Relative fitness, in terms of seed production and subsequent seeding survival, averages 2.4 times that of the uneaten controls. The authors conclude that under natural field conditions plants can benefit from the effects of herbivory.
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