Data from: Interplay of robustness and plasticity of life history traits drives ecotypic differentiation in thermally distinct habitats

Phenotypic plasticity describes the ability of an individual to alter its phenotype in response to the environment and is potentially adaptive when dealing with environmental variation. However, robustness in the face of a changing environment may often be beneficial for traits that are tightly linked to fitness. We hypothesized that robustness of some traits may depend on specific patterns of plasticity within and among other traits. We used a reaction norm approach to study robustness and phenotypic plasticity of three life history traits of the collembolan Orchesella cincta in environments with different thermal regimes. We measured adult mass, age at maturity and growth rate of males and females from heath and forest habitats at two temperatures (12 and 22 °C). We found evidence for ecotype-specific robustness of female adult mass to temperature, with a higher level of robustness in the heath ecotype. This robustness is facilitated by plastic adjustments of growth rate and age at maturity. Furthermore, female fecundity is strongly influenced by female adult mass, explaining the importance of realizing a high mass across temperatures for females. These findings indicate that different predicted outcomes of life history theory can be combined within one species’ ontogeny and that models describing life history strategies should not assume that traits like growth rate are maximized under all conditions. On a methodological note, we report a systematic inflation of variation when standard deviations and correlation coefficients are calculated from family means as opposed to individual data within a family structure.表型可塑性（phenotypic plasticity）指个体响应环境变化而改变自身表型的能力，在应对环境变异时具备潜在适应性。然而，面对多变环境时，与适合度（fitness）紧密关联的性状往往会从鲁棒性（robustness）中获益。我们提出假说：部分性状的鲁棒性可能依赖于其他性状内部及性状间的特定可塑性模式。本研究采用反应规范（reaction norm）方法，针对弹尾虫（collembolan）钩棘跳虫（Orchesella cincta）的三种生活史性状，在不同温度制度环境下开展鲁棒性与表型可塑性研究。我们设置12 ℃与22 ℃两个温度梯度，测量了来自石楠生境与森林生境的雌雄个体的成虫体重、成熟年龄及生长速率。研究发现，雌性成虫体重对温度的鲁棒性存在生态型（ecotype）特异性：石楠生态型的鲁棒性水平更高，该鲁棒性通过生长速率与成熟年龄的可塑性调控得以实现。此外，雌性繁殖力（fecundity）受成虫体重的影响极强，这解释了雌性个体在不同温度下均需达到较高体重的重要性。本研究结果表明，生活史理论（life history theory）的不同预测结果可在同一物种的个体发育（ontogeny）过程中得以结合，且描述生活史策略的模型不应假设生长速率等性状在所有条件下均被最大化。在方法学层面，我们报告了一种系统偏差：当从家系均值而非家系内的个体数据计算标准差（standard deviation）与相关系数（correlation coefficient）时，会出现变异的系统性膨胀。