Adaptation to drought is coupled with slow growth, but independent from phenology in marginal silver fir (Abies alba Mill.) populations

Drought is one of the most important selection pressures for forest trees in the context of climate change. Yet, the different evolutionary mechanisms, and their environmental drivers, by which certain populations become more drought tolerant than others is still little understood. We studied adaptation to drought in 16 silver fir (Abies alba Mill.) populations from the French Mediterranean Alps by combining observations on seedlings from a large scale greenhouse experiment (N=8199) and on adult tress in situ (N=315). In the greenhouse, we followed half-sib families for four growing seasons for growth traits and bud break phenology, and tested their water stress response in a \"drought until death\" experiment. Adult trees in the field were assessed for δ13C, a proxy for water use efficiency and genotyped at 357 SNP loci. SNP data was used to generate a null expectation for trait divergence between populations to detect the signature of selection, and 31 environmental variables to identif...在气候变化背景下，干旱是林木面临的最关键选择压力之一。然而，为何部分种群的耐旱性优于其他种群？其背后的不同进化机制及环境驱动因素仍鲜为人知。我们以法国地中海阿尔卑斯山区的16个欧洲冷杉（silver fir，Abies alba Mill.）种群为研究对象，结合大型温室试验（样本量N=8199）的幼苗观测数据与原位成年林木（N=315）的观测数据，探究其干旱适应机制。温室试验中，我们对半同胞家系开展了四个生长季的观测，记录其生长性状与芽萌物候期，并通过"干旱直至死亡"试验测定其水分胁迫响应。对野外成年林木，我们测定了其δ¹³C（作为水分利用效率的替代指标），并在357个单核苷酸多态性（Single Nucleotide Polymorphism，SNP）位点进行基因分型。我们利用SNP数据构建种群间性状分化的零假设模型，以检测选择信号；同时结合31个环境变量以识别...