Leroy Thibault, Louvet Jean-Marc, Lalanne Céline, Le Provost Grégoire, Labadie Karine, Aury Jean-Marc, Delzon Sylvain, Plomion Christophe, Kremer Antoine
BIOGECO, INRA, Université de Bordeaux, 69 Route d'Arcachon, 33612, Cestas, France.
ISEM, CNRS, IRD, EPHE, University of Montpellier, Place Eugène Bataillon, 34095, Montpellier, France.
New Phytol. 2020 May;226(4):1171-1182. doi: 10.1111/nph.16095. Epub 2019 Sep 20.
Latitudinal and elevational gradients provide valuable experimental settings for studies of the potential impact of global warming on forest tree species. The availability of long-term phenological surveys in common garden experiments for traits associated with climate, such as bud flushing for sessile oaks (Quercus petraea), provide an ideal opportunity to investigate this impact. We sequenced 18 sessile oak populations and used available sequencing data for three other closely related European white oak species (Quercus pyrenaica, Quercus pubescens, and Quercus robur) to explore the evolutionary processes responsible for shaping the genetic variation across latitudinal and elevational gradients in extant sessile oaks. We used phenotypic surveys in common garden experiments and climatic data for the population of origin to perform genome-wide scans for population differentiation and genotype-environment and genotype-phenotype associations. The inferred historical relationships between Q. petraea populations suggest that interspecific gene flow occurred between Q. robur and Q. petraea populations from cooler or wetter areas. A genome-wide scan of differentiation between Q. petraea populations identified single nucleotide polymorphisms (SNPs) displaying strong interspecific relative divergence between these two species. These SNPs followed genetic clines along climatic or phenotypic gradients, providing further support for the likely contribution of introgression to the adaptive divergence of Q. petraea populations. Overall, the results indicate that outliers and associated SNPs are Q. robur ancestry-informative. We discuss the results of this study in the framework of the postglacial colonization scenario, in which introgression and diversifying selection have been proposed as essential drivers of Q. petraea microevolution.
纬度和海拔梯度为研究全球变暖对森林树种的潜在影响提供了宝贵的实验环境。在常见园圃实验中，针对与气候相关的性状（如无柄栎（Quercus petraea）的芽萌发）进行长期物候调查，为研究这种影响提供了理想机会。我们对18个无柄栎种群进行了测序，并利用其他三种欧洲近缘白栎树种（比利牛斯栎（Quercus pyrenaica）、柔毛栎（Quercus pubescens）和夏栎（Quercus robur））的现有测序数据，来探究塑造现存无柄栎在纬度和海拔梯度上遗传变异的进化过程。我们在常见园圃实验中进行了表型调查，并利用种群原生地的气候数据进行全基因组扫描，以分析种群分化以及基因型与环境和基因型与表型的关联。推断出的无柄栎种群之间的历史关系表明，在较凉爽或较湿润地区的夏栎和无柄栎种群之间发生了种间基因流动。对无柄栎种群间分化的全基因组扫描识别出了单核苷酸多态性（SNP），这些SNP在这两个物种之间显示出强烈的种间相对差异。这些SNP沿着气候或表型梯度呈现遗传渐变，为渐渗杂交对无柄栎种群适应性分化的可能贡献提供了进一步支持。总体而言，结果表明异常值和相关的SNP具有夏栎祖先信息。我们在冰期后殖民情景的框架内讨论了本研究的结果，在该情景中，渐渗杂交和多样化选择被认为是无柄栎微进化的重要驱动因素。
