While a plant's capacity to tolerate damage by herbivores can be studied as a single trait, it is important to recognize that tolerance is generally a result of the combined action of several different traits. Here, we report on a pair of experiments to identify mechanisms for tolerating floral herbivory in Solanum carolinense, an andromonoecious perennial herb that regularly suffers from high levels of florivory. We measured the effect of actual and simulated florivory on host-plant fitness and assessed which plant traits exhibited plasticity in response to florivory. In addition, for each of nine plant genets, we calculated tolerance indices and determined which traits were genetically correlated with tolerance. Traits that served to help S. carolinense tolerate florivory in terms of sexual reproduction included initiating more inflorescences, aborting fewer buds prior to anthesis and fewer ovaries after

Summary 1The series of steps used to regulate a plant's investment in reproduction in response to environmental stresses is a life-history strategy critical to maximizing fitness. We investigated how the andromonoecious herb Solanum carolinense regulates its maternal investment in response to stress from foliar and floral herbivory. 2 Most of the variation among S. carolinense individuals (ramets) in maternal investment occurred during the initiation of flower-bud primordia, with ramets initiating between 9 and 167 flower buds. 3 In response to simulated floral herbivory, S. carolinense regulated maternal investment by decreasing the abortion rate of flower buds, increasing the ratio of perfect to male flowers and decreasing the rate of fruit abortion. 4 In response to foliar herbivory, the plants increased the rate of fruit abortion and decreased allocation to perennial root growth. 5 Some individuals specialized at regulating during early phenological stages, others specialized at later regulation, and there appeared to be trade-offs between these strategies. 6 Because most plants must cope with multiple stresses that occur at different times in their phenology, such trade-offs suggest the presence of adaptive constraints. In particular, a plant's ability to tolerate damage by one species of herbivore may be constrained by the cost of lower tolerance of the damage caused by the other herbivores that feed on the plant.

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