Data from: Adaptive divergence in flowering time among natural populations of Arabidopsis thaliana: estimates of selection and QTL mapping

To identify the ecological and genetic mechanisms of local adaptation requires estimating selection on traits, identifying their genetic basis, and evaluating whether divergence in adaptive traits is due to conditional neutrality or genetic tradeoffs. To this end, we conducted field experiments for three years using recombinant inbred lines derived from two ecotypes of Arabidopsis thaliana (Italy, Sweden), and at each parental site examined selection on flowering time and mapped QTL. There was strong selection for early flowering in Italy, but weak selection in Sweden. Eleven distinct flowering time QTL were detected, and for each the Italian genotype caused earlier flowering. Twenty-seven candidate genes were identified, two of which (FLC and VIN3) appear under major flowering time QTL in Italy. Seven of eight QTL in Italy with narrow credible intervals colocalized with previously reported fitness QTL, in comparison to three of four in Sweden. The results demonstrate that the magnitude of selection on flowering time differs strikingly between our study populations, that the genetic basis of flowering time variation is multigenic with some QTL of large effect, and suggest that divergence in flowering time between ecotypes is due mainly to conditional neutrality.

要解析本地适应的生态与遗传机制，需估算性状所受的选择压、明确其遗传基础，并评估适应性性状的分化是源于条件中性还是遗传权衡。为此，我们利用源自两种拟南芥（Arabidopsis thaliana）生态型——意大利生态型与瑞典生态型——的重组自交系，开展了为期三年的田间试验，并在每个亲本种群的原生境中检测开花时间所受的选择压、定位数量性状位点（Quantitative Trait Locus，QTL）。在意大利原生境中，提早开花的性状受到强烈选择，而在瑞典原生境中选择压较弱。本研究共检测到11个独立的开花时间相关QTL，且所有QTL的意大利等位基因均可促使植株提早开花。此外，我们鉴定出27个候选基因，其中两个基因（FLC与VIN3）似乎位于意大利种群中效应显著的开花时间QTL区域内。意大利种群中8个具有狭窄置信区间的QTL里，有7个与此前报道的适合度QTL共定位；而瑞典种群的4个QTL中则有3个存在共定位现象。本研究结果表明：两个研究种群间，开花时间所受选择压的差异极为显著；开花时间的变异具有多基因调控的遗传基础，且存在部分效应较强的QTL；此外，两种生态型的开花时间分化主要源于条件中性机制。