Centre d'Écologie Fonctionnelle et Évolutive, CNRS, Université de Montpellier, Université Paul Valéry Montpellier 3, École Pratique des Hautes Études | Paris Science et Lettres, Institut de Recherche pour le Développement, 34000 Montpellier, France;
Institut de Systématique, Évolution, Biodiversité, École Pratique des Hautes Études | Paris Sciences et Lettres, Muséum National d'Histoire Naturelle, CNRS, Sorbonne Université, Université des Antilles, 75005 Paris, France.
Proc Natl Acad Sci U S A. 2020 Dec 15;117(50):31969-31978. doi: 10.1073/pnas.2009003117. Epub 2020 Nov 30.
Temporal variation in natural selection is predicted to strongly impact the evolution and demography of natural populations, with consequences for the rate of adaptation, evolution of plasticity, and extinction risk. Most of the theory underlying these predictions assumes a moving optimum phenotype, with predictions expressed in terms of the temporal variance and autocorrelation of this optimum. However, empirical studies seldom estimate patterns of fluctuations of an optimum phenotype, precluding further progress in connecting theory with observations. To bridge this gap, we assess the evidence for temporal variation in selection on breeding date by modeling a fitness function with a fluctuating optimum, across 39 populations of 21 wild animals, one of the largest compilations of long-term datasets with individual measurements of trait and fitness components. We find compelling evidence for fluctuations in the fitness function, causing temporal variation in the magnitude, but not the direction of selection. However, fluctuations of the optimum phenotype need not directly translate into variation in selection gradients, because their impact can be buffered by partial tracking of the optimum by the mean phenotype. Analyzing individuals that reproduce in consecutive years, we find that plastic changes track movements of the optimum phenotype across years, especially in bird species, reducing temporal variation in directional selection. This suggests that phenological plasticity has evolved to cope with fluctuations in the optimum, despite their currently modest contribution to variation in selection.
自然选择的时间变化预计将强烈影响自然种群的进化和种群动态，从而影响适应速度、可塑性进化和灭绝风险。这些预测背后的大部分理论都假设最优表型是移动的，并且预测是根据最优表型的时间方差和自相关来表达的。然而，实证研究很少估计最优表型波动的模式，从而阻碍了将理论与观察结果联系起来的进一步进展。为了弥合这一差距，我们通过在 39 个 21 种野生动物种群中构建具有波动最优值的适应值函数，评估了对繁殖日期选择的时间变化的证据，这是对具有个体特征和适应值组件的长期数据集进行的最大规模综合之一。我们发现了有力的证据表明适应值函数存在波动，导致选择幅度发生时间变化，但选择方向不变。然而，最优表型的波动不一定直接转化为选择梯度的变化，因为它们的影响可以通过平均表型对最优值的部分跟踪来缓冲。分析连续多年繁殖的个体，我们发现，在鸟类等物种中，可塑性变化会跟踪多年来最优表型的变化，从而减少了定向选择的时间变化。这表明尽管最优表型的波动对选择变化的贡献目前还不大，但表型的生理可塑性已经进化到可以应对最优表型的波动。
