Data from: The alignment between phenotypic plasticity, the major axis of genetic variation and the response to selection

Phenotypic plasticity is the ability of a genotype to produce more than one phenotype in order to match the environment. Recent theory proposes that the major axis of genetic variation in a phenotypically plastic population can align with the direction of selection. Therefore, theory predicts that plasticity directly aids adaptation by increasing genetic variation in the direction favoured by selection and reflected in plasticity. We evaluated this theory in the freshwater crustacean Daphnia pulex, facing predation risk from two contrasting size-selective predators. We estimated plasticity in several life history traits, the G matrix of these traits, the selection gradients on reproduction and survival and the predicted responses to selection. Using these data, we tested whether the genetic lines of least resistance and the predicted response to selection aligned with plasticity. We found predator environment-specific G matrices, but shared genetic architecture across environments resulted in more constraint in the G matrix than in the plasticity of the traits, sometimes preventing alignment of the two. However, as the importance of survival selection increased, the difference between environments in their predicted response to selection increased and resulted in closer alignment between plasticity and the predicted selection response. Therefore, plasticity may indeed aid adaptation to new environments.

表型可塑性（phenotypic plasticity）指的是基因型为适配环境而表达多种表型的能力。近期的理论提出，在具有表型可塑性的种群中，遗传变异的主轴线可与选择方向保持一致。因此，该理论预测，可塑性可通过增加选择偏好且在可塑性中体现的方向上的遗传变异，直接助力适应性进化。我们以淡水甲壳类动物蚤状溞（Daphnia pulex）为研究对象，评估该理论，该种群面临两种截然不同的体型选择性捕食者的捕食风险。我们估算了多个生活史性状的可塑性、这些性状的G矩阵（G matrix）、繁殖与存活的选择梯度以及预测的选择响应。基于这些数据，我们检验了最小抵抗遗传轴线与预测的选择响应是否与可塑性保持一致。我们发现了捕食者环境特异性的G矩阵，但不同环境间共享的遗传结构使得G矩阵相较于性状可塑性受到更多约束，有时会阻碍二者的一致性。然而，随着存活选择的重要性提升，不同环境间的预测选择响应差异随之增大，使得可塑性与预测的选择响应之间的一致性更为紧密。因此，表型可塑性确实可助力种群适应新环境。