Phenotypic differences among populations stem from the interaction between neutral and adaptive processes, and phenotypic plasticity. Although clinal trait variation along climatic gradients often evolves in widely distributed species, it is unknown whether substrate specialization, such as that of Mediterranean gypsum plants, has constrained adaptation to climate. Using a common garden experiment with two contrasting watering treatments, we quantified phenotypic plasticity, assessed evidence for footprints of selection using FST – QST comparisons, and evaluated the ecological factors driving genetically based phenotypic differentiation of 11 populations encompassing the full environmental range of the gypsum shrub Lepidium subulatum. We found evidence for genetic differentiation among populations related to climatic differences, with populations from warmer and drier sites showing lower specific leaf area and leaf N, earlier phenology, greater water use efficiency and greater fitness. Multiple lines of evidence suggest that this differentiation was driven by past divergent selection rather than neutral processes. All populations showed high phenotypic plasticity, indicating that plasticity has not been selected against, even in populations from sites with harsher climatic conditions. Synthesis. Our results indicate that despite strong substrate specialization, adaptive differentiation related to climatic gradients occurs in this species. However, we also found that populations from mesic sites may be particularly vulnerable to future climate change given their relatively lower fitness under both wet and dry conditions.

中文翻译：

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范围广泛的种内变异反映了地中海满天星灌木过去对气候的适应

群体之间的表型差异源于中性和适应性过程以及表型可塑性之间的相互作用。尽管沿气候梯度的临床性状变异通常在广泛分布的物种中进化，但目前尚不清楚基质特化（例如地中海石膏植物的基质特化）是否限制了对气候的适应。 使用具有两种对比浇水处理的常见花园实验，我们量化了表型可塑性，使用以下方法评估了选择足迹的证据F英石–问英石比较，并评估了驱动石膏灌木整个环境范围的 11 个种群基于遗传的表型分化的生态因素独行菜（Lepidium subulatum）。 我们发现了与气候差异相关的种群遗传分化的证据，来自温暖和干燥地区的种群表现出较低的比叶面积和叶氮、较早的物候、较高的水分利用效率和较高的适应性。多种证据表明，这种分化是由过去的分歧选择而不是中性过程驱动的。所有种群都表现出高表型可塑性，表明可塑性没有被选择，即使是来自气候条件较恶劣地区的种群。 合成。我们的结果表明，尽管有很强的基质特化，但该物种仍发生与气候梯度相关的适应性分化。然而，我们还发现，由于湿地和干燥条件下的适应性相对较低，来自湿地的人口可能特别容易受到未来气候变化的影响。