Data from: Paths to selection on life history loci in different natural environments across the native range of Arabidopsis thaliana

Selection on quantitative trait loci (QTL) may vary among natural environments due to differences in the genetic architecture of traits, environment-specific allelic effects or changes in the direction and magnitude of selection on specific traits. To dissect the environmental differences in selection on life history QTL across climatic regions, we grew a panel of interconnected recombinant inbred lines (RILs) of Arabidopsis thaliana in four field sites across its native European range. For each environment, we mapped QTL for growth, reproductive timing and development. Several QTL were pleiotropic across environments, three colocalizing with known functional polymorphisms in flowering time genes (CRY2, FRI and MAF2-5), but major QTL differed across field sites, showing conditional neutrality. We used structural equation models to trace selection paths from QTL to lifetime fitness in each environment. Only three QTL directly affected fruit number, measuring fitness. Most QTL had an indirect effect on fitness through their effect on bolting time or leaf length. Influence of life history traits on fitness differed dramatically across sites, resulting in different patterns of selection on reproductive timing and underlying QTL. In two oceanic field sites with high prereproductive mortality, QTL alleles contributing to early reproduction resulted in greater fruit production, conferring selective advantage, whereas alleles contributing to later reproduction resulted in larger size and higher fitness in a continental site. This demonstrates how environmental variation leads to change in both QTL effect sizes and direction of selection on traits, justifying the persistence of allelic polymorphism at life history QTL across the species range.

由于性状的遗传架构、环境特异性等位基因效应，或特定性状上选择的方向与强度存在差异，自然环境下对数量性状位点（quantitative trait loci，QTL）的选择可能有所不同。为解析不同气候区域内生活史数量性状位点上选择的环境差异，我们在拟南芥（Arabidopsis thaliana）原生分布范围的欧洲地区的4个野外试验点，种植了一组相互关联的重组自交系（recombinant inbred lines，RILs）。针对每个试验环境，我们对生长、生殖时序与发育相关的性状进行了数量性状位点定位。多个数量性状位点在不同环境中表现出多效性，其中3个与已知的开花时间功能多态位点（CRY2、FRI及MAF2-5）共定位，但主要的数量性状位点在各野外试验点间存在差异，呈现条件中性现象。我们采用结构方程模型（structural equation models），追踪了各环境下从数量性状位点到终生适合度的选择通路。仅有3个数量性状位点可直接影响作为适合度指标的结实数。绝大多数数量性状位点通过影响抽苔时间或叶长，对适合度产生间接效应。不同试验点的生活史性状对适合度的影响差异显著，进而导致生殖时序及相关数量性状位点上的选择模式各不相同。在两个存在较高生殖前死亡率的海洋性野外试验点中，促进早期生殖的数量性状位点等位基因可提升结实数，从而赋予选择优势；而在一个大陆性试验点中，促进后期生殖的等位基因则会使植株体型更大，适合度更高。该研究表明，环境变异可同时改变数量性状位点的效应强度与性状选择方向，这也解释了为何在整个物种分布范围内，生活史数量性状位点上的等位基因多态性得以维持。