Plastic bet-hedging in an amphicarpic annual as an integrated strategy under variable conditions

Amphicarpy is a form of diversified bet-hedging, producing two types of offspring with two distinct ecological roles. We empirically tested a recent theory predicting the integration of plasticity and bet-hedging by studying the response of the offspring ratio of an amphicarpic annual to different environmental conditions. We conducted a greenhouse experiment, manipulating nutrient availability and intraspecific density, to detect such integration. In order to determine whether the integrated strategy is an adaptation to variable habitats, a similar common garden experiment was conducted comparing two natural populations differing in environmental variability. We detected increasing plasticity in the offspring ratio with increased heterogeneity of the habitat of origin. Plasticity was asymmetric, but evident in both offspring types. We found evidence for an adaptive integrated strategy. This study brings rare evidence for the recent Theory of Multimoment Reaction Norms, within the context of classical bet-hedging theory. We suggest relationships between colonization opportunities, dispersal risks, mother-site control and sib-sib competition as more proximate ecological mechanisms that may give rise to this integrated strategy in our model species.