Resource availability and predator cues shape within- and transgenerational reaction norms

Abstract

The main dilemma facing prey is how to reduce predation risk while acquiring resources. Phenotypic plasticity, by modulating traits for acquiring resources and for defences, is a key process driving this trade-off. While there is ample evidence that predator-induced within-generational plasticity depends on resources, the relationship between resources and predator-induced transgenerational plasticity (TGP) remains understudied. This study investigated how predator exposure and resource availability influence within-generational plasticity and TGP. We based our predictions on theories related to information- and state-based plasticity, two kinds of plasticity occurring in response to environmental information or alteration affecting somatic state, respectively. We conducted a two-generation laboratory experiment in the freshwater snail Physa acuta, manipulating predator cues and resource availability. Our results revealed that both types of plasticity participate in shaping the within- and transgenerational responses. Within a generation, the limited resource decreased the somatic state but did not constrain the defences. Across generations, the poor parental state decreased the offspring state even in high-resource conditions, which in turn decreased the absolute levels of their defences but increased their investment in reproduction. These results highlight the importance of integrating informational and state-based effects across generations to provide a more complete understanding of prey responses to predators.