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.诸多已有研究证实，环境能够诱导表型产生可跨越多代的非遗传变异。相关理论预测，可预测的环境波动会同时增强当代可塑性（within-generation plasticity）与跨代可塑性（transgenerational plasticity）的响应能力。然而，据我们所知，目前尚无针对该理论预测的实证检验。本研究以奇异溞（Daphnia ambigua）为研究对象，通过评估捕食者信号（predator cues）对其生活史性状（life-history traits）的影响，探究了当代可塑性与跨代可塑性之间的关联。本研究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。研究结果显示，胚胎发育阶段的捕食者暴露会促使个体更早成熟，并提升繁殖产出。此类效应在脱离捕食者暴露的两代后仍可被检测到，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，当代可塑性响应与跨代可塑性响应之间呈负相关关系，换言之，针对捕食者信号的当代响应与跨代响应在方向与强度上均呈相反特征。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当代与跨代可塑性之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体系的必要性。