How does the somatic state influence plastic responses to predator cues within- and across generations?

The rapid environmental changes challenge organisms that must cope with multiple changing factors. In this ecological context, phenotypic plasticity allows organisms to rapidly react. It can occur, both within- and across generations, as a response to environmental information or to environmental quality affecting individual somatic state. Information- and state-based plasticity have largely been investigated independently, which limits theoretical developments and empirical result interpretation. In this study, we investigate the interaction between these two types of plasticity in the context of anti-predator defences, using a two-generation laboratory experiment in the snail Physa acuta. Our results revealed that both types of plasticity participate in shaping the within- and transgenerational responses. Within a generation, the limited resource decreases the individuals somatic state but did not constrain the costly expression of defences. Across generations, the poor state of parents decreased the offspring state, which in turn decreased the absolute levels of their defences. The lower defences of offspring from low-resource parents were, however, compensated by a higher reproductive success. By illustrating the intimately intertwining between information- and state-based plasticity, our study calls for increased study integrating their complex interactions to improve research about the role of phenotypic plasticity in ecology and evolution.