Department of Biodiversity and Evolutionary Biology, Museo Nacional de Ciencias Naturales (MNCN-CSIC), José Gutiérrez Abascal, Madrid, Spain.
Department of Biodiversity and Ecologic Restoration, Instituto Pirenaico de Ecología (IPE-CSIC), Avda. Nuestra Señora de la Victoria, Jaca, Spain.
Ann Bot. 2021 Mar 24;127(4):413-423. doi: 10.1093/aob/mcaa096.
It is widely accepted that changes in the environment affect mean trait expression, but little is known about how the environment shapes intra-individual and intra-population variance. Theory suggests that intra-individual variance might be plastic and under natural selection, rather than reflecting developmental noise, but evidence for this hypothesis is scarce. Here, we experimentally tested whether differences in intrinsic environmental predictability affect intra-individual and intra-population variability of different reproductive traits, and whether intra-individual variability is under selection.
Under field conditions, we subjected Onobrychis viciifolia to more and less predictable precipitation over 4 generations and 4 years. We analysed effects on the coefficient of intra-individual variation (CVi-i) and the coefficient of intra-population variation (CVi-p), assessed whether the coefficients of intra-individual variation (CsVi-i) are under natural selection and tested for transgenerational responses (ancestor environmental effects on offspring).
Less predictable precipitation led to higher CsVi-i and CsVi-p, consistent with plastic responses. The CsVi-i of all studied traits were under consistent stabilizing selection, and precipitation predictability affected the strength of selection and the location of the optimal CVi-i of a single trait. All CsVi-i differed from the optimal CVi-i and the maternal and offspring CsVi-i were positively correlated, showing that there was scope for change. Nevertheless, no consistent transgenerational effects were found in any of the three descendant generations, which contrasts with recent studies that detected rapid transgenerational responses in the trait means of different plant species. This suggests that changes in intra-individual variability take longer to evolve than changes in trait means, which may explain why high intra-individual variability is maintained, despite the stabilizing selection.
The results indicate that plastic changes of intra-individual variability are an important determinant of whether plants will be able to cope with changes in environmental predictability induced by the currently observed climatic change.
环境变化会影响平均特征表达，这一观点已被广泛接受，但对于环境如何塑造个体内和群体内方差知之甚少。理论表明，个体内方差可能具有可塑性，并受到自然选择的影响，而不是反映发育噪声，但这一假设的证据很少。在这里，我们通过实验测试了内在环境可预测性的差异是否会影响不同生殖特征的个体内和群体内变异性，以及个体内变异性是否受到选择。
在野外条件下，我们让苦马豆在 4 代和 4 年内经历更多和更少可预测的降水。我们分析了对个体内变异系数（CVi-i）和群体内变异系数（CVi-p）的影响，评估了个体内变异系数（CsVi-i）是否受到自然选择的影响，并测试了跨代响应（祖先环境对后代的影响）。
较少可预测的降水导致更高的 CsVi-i 和 CsVi-p，这与可塑性反应一致。所有研究特征的 CsVi-i 都受到一致的稳定选择，降水可预测性影响单一特征的选择强度和最优 CVi-i 的位置。所有 CsVi-i 都与最优 CVi-i 不同，并且母体和后代 CsVi-i 呈正相关，表明存在变化的空间。然而，在三个后代中没有发现一致的跨代效应，这与最近的研究形成对比，后者在不同植物物种的性状平均值中检测到了快速的跨代响应。这表明，与性状平均值的变化相比，个体内变异性的变化需要更长的时间才能进化，这可能解释了为什么尽管存在稳定选择，但仍保持较高的个体内变异性。
研究结果表明，个体内变异性的可塑性变化是植物是否能够应对当前观察到的气候变化引起的环境可预测性变化的一个重要决定因素。
