Long‐term environmental variation often drives local adaptation and leads to trait differentiation across populations. Additionally, when traits change in an environment‐dependent way through phenotypic plasticity, the genetic variation underlying plasticity will also be under selection. These processes could create a landscape of differentiation across populations in traits and their plasticity. Here, we performed a dry‐down experiment under controlled conditions to measure responses in seedlings of a shrub species from the Cape Floristic Region, the common sugarbush (Protea repens). We measured morphological and physiological traits, and sequenced whole transcriptomes of leaf tissues from eight populations that represent both the climatic and the geographical distribution of this species. We found that there is substantial variation in how populations respond to drought, but we also observed common patterns such as reduced leaf size and leaf thickness, and up‐regulation of stress‐related and down‐regulation of growth‐related gene groups. Both high environmental heterogeneity and milder source site climates were associated with higher plasticity in various traits and co‐expression gene networks. Associations between traits, trait plasticity, gene networks and the source site climate suggest that temperature may play a greater role in shaping these patterns when compared to precipitation, in line with recent changes in the region due to climate change. We also found that traits respond to climatic variation in an environment‐dependent manner: some associations between traits and climate were apparent only under certain growing conditions. Together, our results uncover common responses of P. repens populations to drought, and climatic drivers of population differentiation in functional traits, gene expression and their plasticity.

中文翻译：

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气候解释了南非普罗蒂亚地区干旱诱导的功能性状和基因表达的可塑性差异

长期的环境变化经常推动局部适应，并导致种群间的性状分化。此外，当性状通过表型可塑性以环境相关的方式改变时，可塑性下的遗传变异也将处于选择之中。这些过程可能会在性状及其可塑性方面创造出不同人群的差异化景观。在这里，我们在受控条件下进行了干燥实验，以测量佛得角海角灌木丛（Protea repens）的灌木物种的幼苗中的响应）。我们测量了形态和生理特征，并对来自八个种群的叶片组织的完整转录组进行了测序，这些种群代表了该物种的气候和地理分布。我们发现种群对干旱的反应方式存在很大差异，但我们也观察到了常见的模式，例如叶片尺寸和叶片厚度减小，与压力相关的上调和与生长相关的基因组的下调。较高的环境异质性和较温和的源站点气候都与各种性状和共表达基因网络的较高可塑性有关。性状，性状可塑性，基因网络和源站点气候之间的关联表明，与降水相比，温度在塑造这些模式方面可能发挥更大的作用，与该地区最近因气候变化而发生的变化一致。我们还发现，性状以与环境相关的方式响应气候变化：性状与气候之间的某些关联仅在某些生长条件下才明显。我们的结果共同揭示了P.使种群趋于干旱，是种群在功能性状，基因表达及其可塑性方面分化的气候驱动因素。