Data from: Adaptive value of phenological traits in stressful environments: predictions based on seed production and laboratory natural selection

Phenological traits often show variation within and among natural populations of annual plants. Nevertheless, the adaptive value of post-anthesis traits is seldom tested. In this study, we estimated the adaptive values of pre- and post-anthesis traits in two stressful environments (water stress and interspecific competition), using the selfing annual species Arabidopsis thaliana. By estimating seed production and by performing laboratory natural selection (LNS), we assessed the strength and nature (directional, disruptive and stabilizing) of selection acting on phenological traits in A. thaliana under the two tested stress conditions, each with four intensities. Both the type of stress and its intensity affected the strength and nature of selection, as did genetic constraints among phenological traits. Under water stress, both experimental approaches demonstrated directional selection for a shorter life cycle, although bolting time imposes a genetic constraint on the length of the interval between bolting and anthesis. Under interspecific competition, results from the two experimental approaches showed discrepancies. Estimation of seed production predicted directional selection toward early pre-anthesis traits and long post-anthesis periods. In contrast, the LNS approach suggested neutrality for all phenological traits. This study opens questions on adaptation in complex natural environment where many selective pressures act simultaneously.物候性状（phenological traits）在一年生植物的自然种群内部及种群间普遍存在变异。然而，花后性状（post-anthesis traits）的适应价值却极少得到系统性检验。本研究以自交一年生物种拟南芥（Arabidopsis thaliana）为实验材料，在两种胁迫环境——水分胁迫（water stress）与种间竞争（interspecific competition）——中评估了花前与花后性状的适应价值。通过估算种子产量（seed production）并开展实验室自然选择（laboratory natural selection, LNS）实验，我们在两种各设置四个强度梯度的胁迫条件下，量化了拟南芥物候性状所受选择的强度与类型（定向选择（directional selection）、分裂选择（disruptive selection）与稳定选择（stabilizing selection））。胁迫类型及其强度均会显著影响选择的强度与类型，物候性状间的遗传约束（genetic constraints）同样会对选择模式产生调控作用。在水分胁迫条件下，两种实验方法均证实存在对更短生活周期的定向选择，尽管抽薹时间（bolting time）会对抽薹至开花的间隔时长施加遗传约束。在种间竞争条件下，两种实验方法的结果存在明显分歧：种子产量估算结果预测，选择会偏向于早花前性状与长花后周期的方向；而实验室自然选择实验则表明所有物候性状均处于中性选择状态。本研究为解析多种选择压力协同作用下复杂自然环境中的适应性演化机制提出了诸多待解科学问题。