Data from: Predator-induced phenotypic plasticity within- and across-generations: a challenge for theory?

Much work has shown that the environment can induce non-genetic changes in phenotype that span multiple generations. Theory predicts that predictable environmental variation selects for both increased within- and across-generation responses. Yet, to the best of our knowledge, there are no empirical tests of this prediction. We explored the relationship between within- versus across-generation plasticity by evaluating the influence of predator cues on the life-history traits of Daphnia ambigua. We measured the duration of predator-induced transgenerational effects, determined when transgenerational responses are induced, and quantified the cues that activate transgenerational plasticity. We show that predator exposure during embryonic development causes earlier maturation and increased reproductive output. Such effects are detectable two generations removed from predator exposure and are similar in magnitude in response to exposure to cues emitted by injured conspecifics. Moreover, all experimental contexts and traits yielded a negative correlation between within- versus across-generation responses. That is, responses to predator cues within- and across-generations were opposite in sign and magnitude. Although many models address transgenerational plasticity, none of them explain this apparent negative relationship between within- and across-generation plasticities. Our results highlight the need to refine the theory of transgenerational plasticity.

诸多研究已证实，环境能够诱导跨越多代的表型（phenotype）非遗传变化。相关理论预测，可预测的环境变异会同时促进代内响应与跨代响应的增强。然而，据我们所知，目前尚无针对该理论预测的实证检验。我们通过评估捕食者信号（predator cues）对偏角溞（Daphnia ambigua）生活史性状（life-history traits）的影响，探究了代内可塑性（within-generation plasticity）与跨代可塑性（transgenerational plasticity）之间的关联。我们测定了捕食者诱导的跨代效应持续时长，明确了跨代响应的诱导时机，并量化了激活跨代可塑性的信号类型。研究发现，胚胎发育阶段的捕食者暴露会使个体成熟提前，生殖产出提升。此类效应在脱离捕食者暴露环境的两代个体中仍可被检测到，且其效应强度与暴露于受伤同种个体释放的信号时相当。此外，所有实验情境与性状均显示代内与跨代响应之间存在负相关：即对捕食者信号的代内响应与跨代响应在方向与强度上均呈相反关系。尽管已有诸多模型针对跨代可塑性展开研究，但尚无模型能够解释代内与跨代可塑性间的这一显著负相关关系。本研究结果凸显了完善跨代可塑性理论的必要性。