Transgenerational plasticity of inducible defences: Combined effects of grand-parental, parental and current environments.

Juliette Tariel,Émilien Luquet,Sandrine Plénet

doi:10.1002/ece3.6046

Abstract

Phenotypic plasticity can occur across generations (transgenerational plasticity) when environments experienced by the previous generations influenced offspring phenotype. The evolutionary importance of transgenerational plasticity, especially regarding within‐generational plasticity, is a currently hot topic in the plasticity framework. How long an environmental effect can persist across generations and whether multigenerational effects are cumulative are primordial—for the evolutionary significance of transgenerational plasticity—but still unresolved questions. In this study, we investigated how the grand‐parental, parental and offspring exposures to predation cues shape the predator‐induced defences of offspring in the Physa acuta snail. We expected that the offspring phenotypes result from a three‐way interaction among grand‐parental, parental and offspring environments. We exposed three generations of snails without and with predator cues according to a full factorial design and measured offspring inducible defences. We found that both grand‐parental and parental exposures to predator cues impacted offspring antipredator defences, but their effects were not cumulative and depended on the defences considered. We also highlighted that the grand‐parental environment did alter reaction norms of offspring shell thickness, demonstrating an interaction between the grand‐parental transgenerational plasticity and the within‐generational plasticity. We concluded that the effects of multigenerational exposure to predator cues resulted on complex offspring phenotypic patterns which are difficult to relate to adaptive antipredator advantages.

Highlights

Organisms may respond to fluctuating environments by adapting through genetic evolution over generations or through phenotypic plasticity
The offspring exposure to predator cues significantly decreased by 18% the snail weight (Table 1b; Fig. 2b)
Three generations are needed after removing predators for the frequency of winged phenotypes to come back to the control level, and this number of generations increases with the induction time. These results suggest that multigenerational environmental effects on inducible defenses are broader than just a parental effect and could persist for many generations

Summary

Introduction

Organisms may respond to fluctuating environments by adapting through genetic evolution over generations or through phenotypic plasticity. This last is traditionally defined as the capacity of a given genotype to render alternative phenotypes under different environmental conditions (within-generational plasticity, WGP) (WestEberhard 2003; Pigliucci 2005). Plasticity may occur across generations (transgenerational plasticity, TGP), when the phenotype of offspring is influenced by carry-over effects of past environments experienced by the previous generation(s) (Agrawal et al 1999; Galloway and Etterson 2007; Salinas et al 2013). When past environmental cues provide reliable proxies about future offspring conditions, TGP may enable organisms to cope with fast-changing environments because it refines offspring phenotypes in anticipation of the environmental conditions they are likely to experience (Bonduriansky and Day 2009; Herman and Sultan 2011; Donelson et al 2018)

Methods

Results

Discussion

Conclusion