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.

为阐明本地适应的生态与遗传机制，需对性状的选择压力进行评估，明确其遗传基础，并探究适应性性状的分化究竟源于条件中性（conditional neutrality）还是遗传权衡（genetic tradeoffs）。为此，我们利用源自两种生态型拟南芥（Arabidopsis thaliana，意大利、瑞典种群）的重组自交系，在两个亲本原生境开展了为期三年的田间试验，针对开花时间施加选择压力并进行数量性状基因座（quantitative trait locus, QTL）定位。在意大利种群原生境中，早开花性状受到强烈正向选择，而在瑞典原生境中选择压力微弱。本研究共检测到11个独立的开花时间相关QTL，所有位点的意大利等位基因型均可促使植株提早开花。此外共鉴定出27个候选基因，其中FLC与VIN3两个基因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个置信区间较窄的QTL中，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中仅3个存在共定位现象。本研究结果表明，两个供试种群间开花时间所受选择强度差异显著；开花时间变异的遗传基础为多基因调控，且存在部分效应显著的QTL；同时提示两种生态型的开花时间分化主要源于条件中性机制。