Functional traits are organismal attributes that can respond to environmental cues, thereby providing important ecological functions. In addition, an organism's potential for adaptation is defined by the patterns of covariation among groups of functionally related traits. Whether an organism is evolutionarily constrained or has the potential for adaptation is based on the phenotypic integration or modularity of these traits. Here, we revisited leaf morphology in two European sympatric white oaks (Quercus petraea (Matt.) Liebl. and Quercus robur L.), sampling 2098 individuals, across much of their geographical distribution ranges. At the phenotypic level, leaf morphology traditionally encompasses discriminant attributes among different oak species. Here, we estimated in situ heritability, genetic correlation, and integration across such attributes. Also, we performed Selection Response Decomposition to test these traits for potential differences in oak species' evolutionary responses. Based on the uncovered functional units of traits (modules) in our study, the morphological module "leaf size gradient" was highlighted among functionally integrated traits. Equally, this module was defined in both oaks as being under "global regulation" in vegetative bud establishment and development. Lamina basal shape and intercalary veins' number were not, or, less integrated within the initially defined leaf functional unit, suggesting more than one module within the leaf traits' ensemble. Since these traits generally show the greatest species discriminatory power, they potentially underwent effective differential response to selection among oaks. Indeed, the selection of these traits could have driven the ecological preferences between the two sympatric oaks growing under different microclimates.

中文翻译：

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栎属物种分化是由对进化上整合程度较低的性状的自然选择驱动的

功能性状是可以对环境线索做出反应的有机体属性，从而提供重要的生态功能。此外，生物体的适应潜力是由功能相关性状组之间的共变模式定义的。生物体是否在进化上受到限制或具有适应潜力取决于这些性状的表型整合或模块化。在这里，我们重新审视了两种欧洲同域白橡树（Quercus petraea (Matt.) Liebl. 和 Quercus robur L.）的叶子形态，在其大部分地理分布范围内对 2098 个个体进行了采样。在表型水平上，叶子形态传统上包含不同橡树品种之间的区别属性。在这里，我们估计了原位遗传力、遗传相关性以及这些属性的整合。此外，我们还进行了选择响应分解，以测试这些性状在橡树物种进化反应中的潜在差异。基于我们研究中发现的性状功能单元（模块），形态模块“叶大小梯度”在功能整合性状中突出显示。同样，该模块在两种橡树中都被定义为在营养芽的建立和发育方面处于“全球监管”之下。叶片基部形状和闰脉数量没有或较少整合到最初定义的叶功能单元中，这表明叶性状整体中存在多个模块。由于这些性状通常表现出最大的物种歧视能力，因此它们可能对橡树之间的选择产生有效的差异反应。事实上，这些性状的选择可能驱动了在不同小气候下生长的两种同域橡树之间的生态偏好。