PREMISE OF THE STUDY: Bet-hedging strategies maximize long-term geometric fitness at the cost of reduced arithmetic fitness by offsetting different mortality risks. Heterocarpic systems accomplish bet-hedging through the production of two or more fruit types that vary in dormancy and dispersal ability. It is unknown whether heterocarpy also offsets predispersal mortality risks. To address this question, we investigated whether heterocarpy in Grindelia ciliata (Asteraceae) also offsets mortality risks posed by a seed predator Schinia mortua (Noctuidae) to increase plant fitness. METHODS: We conducted two manipulative experiments to quantify critical life history components of this plant–insect interaction. We measured predispersal achene mortality from herbivory, postdispersal achene mortality in the seed bank, and seedling emergence. These measurements were then used in deterministic models to evaluate evolutionary consequences of predispersal seed mortality in G. ciliata. KEY RESULTS: Dormant achene types were less vulnerable to herbivory but more susceptible to mortality in the seed bank due to delayed seed emergence. Nondormant achene types experienced high predispersal mortality but low seed bank mortality due to rapid germination. Our herbivore-dependent model improved fit between observed and expected proportions of dormant and nondormant G. ciliata achenes and showed that heterocarpy could evolve in the absence of postgermination mortality. CONCLUSIONS: Our study provides empirical support of how predispersal herbivory can be equally important to postdispersal seed mortality risks in the evolution and maintenance of a heterocarpic reproductive system and expands understanding of how bet-hedging theory can be used to understand this unique reproductive strategy.

Herbivory Dependent Bet-Hedging ModelHerbivory Dependent Bet-Hedging ModelHerbTwoYear.BetHedgingModelHerbivory Independent Bet-Hedging ModelHerbivory Independent Bet-Hedging ModelNoHerb.two yearAchene PredictorThis file contains data for a sub-model that is used in Density independent and dependent bet-hedging model. These data must be read in (loaded) prior to running bet hedging models.Achene.cor.predictExtreme Herbivory FrequencyThis file holds code that determines extreme herbivory frequency. This file must be loaded prior to running Herbivory dependent modelBG[]Schinia mortua survivalThis file holds survival data of Schinia mortua larvae placed in Grindelia ciliata capitula.Larval survivalGrindelia ciliata Field EmergenceThis file contains all G. ciliata seedling emergence events.ALL.time.depAchene Consumption by S. mortuaThis file contains the number and proportion of consumed and non-consumed G. ciliata achenes for each of the oviposition treatments.Achene.1Achene Consumption with Capitulum Opening and Inoculation DatesAchene Consumption with Capitulum Opening and Inoculation DatesAchene.11