Offspring reaction norms shaped by parental environment: interaction between within- and trans-generational plasticity of inducible defenses

Abstract

BackgroundWithin-generational plasticity (WGP) and transgenerational plasticity (TGP) are mechanisms allowing rapid adaptive responses to fluctuating environments without genetic change. These forms of plasticity have often been viewed as independent processes. Recent evidence suggests that WGP is altered by the environmental conditions experienced by previous generations (i.e., TGP). In the context of inducible defenses, one of the most studied cases of plasticity, the WGP x TGP interaction has been poorly investigated.ResultsWe provide evidence that TGP can alter the reaction norms of inducible defenses in a freshwater snail. The WGP x TGP interaction patterns are trait-specific and lead to decreased slope of reaction norms (behaviour and shell thickness). Offspring from induced parents showed a higher predator avoidance behaviour and a thicker shell than snails from non-induced parents in no predator-cue environment while they reached similar defenses in predator-cue environment. The WGP x TGP interaction further lead to a switch from a plastic towards a constitutive expression of defenses for shell dimensions (flat reaction norm).ConclusionsWGP-alteration by TGP may shape the adaptive responses to environmental change and then has a substantial importance to understand the evolution of plasticity.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-016-0795-9) contains supplementary material, which is available to authorized users.

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

“…Firstly, these results confirm that offspring reaction norms can be altered by parental environment (shell thickness; Donelson et al, ; Luquet & Tariel, ; Salinas et al, ) but expand for the first time the within‐X transgenerational plasticity interaction to grand‐parental environmental cues (shell thickness). Secondly, the apparent discrepancy between grand‐parental and parental effects for the crawling‐out behavior or the opposing directions found on shell thickness is not rare in empirical studies (Magiafoglou & Hoffmann, ; Shama & Wegner, ) and illustrates the complexity in determining the adaptive significance of multigenerational effects.…”

“…According to a full factorial design, three successive generations of snails from hatching to sexual maturity were exposed or not to predator cues. The results concerning the first two generations have demonstrated a predator‐induced transgenerational plasticity in P. acuta (Luquet & Tariel, ) that has been confirmed in a concomitant study (Beaty et al, ). Here, we focused on the F3 generation to investigate how the effects of grand‐parental, parental and offspring environments combine to influence escape behavior, shell thickness, and shell morphology.…”

“…This suggests that generational cues of crayfish presence can be a good proxy of predation risk across several snail generations and thus that transgenerational plasticity could have long‐lasting effects on the antipredator defences. Consistently, in P. acuta , parental exposure to predator cues induces a more crush‐resistant shell and a higher escape behavior in offspring (Beaty et al, ; Luquet & Tariel, ). In this study, as expected, transgenerational plasticity went further than the parental generation: The grand‐parental environment also influenced the escape behavior and the shell thickness of offspring.…”

“…First, we expected that both grand‐parental and parental exposures to predator cues influence the offspring phenotypes. In addition, as we already observed that parental environment can interact with the offspring environment (Luquet & Tariel, ), we expected that the offspring phenotypes result from a three‐way interaction among grand‐parental, parental and offspring environments.…”

“…acuta (Luquet & Tariel, 2016) that has been confirmed in a concomitant study (Beaty et al, 2016). Here, we focused on the F3 generation to investigate how the effects of grand-parental, parental and offspring environments combine to influence escape behavior, shell thickness, and shell morphology.…”