Data from: Circadian rhythms vary over the growing season and correlate with fitness components

Circadian clocks have evolved independently in all three domains of life, suggesting that internal mechanisms of time-keeping are adaptive in contemporary populations. However, the performance consequences of either discrete or quantitative clock variation have rarely been tested in field settings. Clock sensitivity of diverse segregating lines to the environment remains uncharacterized as do the statistical genetic parameters that determine evolutionary potential. In field studies with Arabidopsis thaliana, we found that major perturbations to circadian cycle length (referred to as clock period) via mutation reduce both survival and fecundity. Subtler adjustments via genomic introgression of naturally occurring alleles indicated that clock periods slightly >24 hrs were adaptive, consistent with prior models describing how well the timing of biological processes is adjusted within a diurnal cycle (referred to as phase). In segregating recombinant inbred lines (RILs), circadian phase varied up to two hours across months of the growing season, and both period and phase expressed significant genetic variances. Performance metrics including developmental rate, size, and fruit set were described by principal components (PC) analyses and circadian parameters correlated with the first PC, such that period lengths slightly >24 hrs were associated with improved performance in multiple RIL sets. These experiments translate functional analyses of clock behavior performed in controlled settings to natural ones, demonstrating that quantitative variation in circadian phase is highly responsive to seasonally variable abiotic factors. The results expand upon prior studies in controlled settings, showing that discrete and quantitative variation in clock phenotypes correlate with performance in nature.生物钟（Circadian clocks）在生命的三大域中均独立演化，这表明内在的计时机制在当代种群中具有适应性。然而，无论是离散型还是数量型生物钟变异对生物体表现的影响，极少在野外环境中得到检验。各类分离群体对环境的生物钟敏感性尚未得到解析，决定演化潜力的统计遗传参数亦未被探明。 在拟南芥（Arabidopsis thaliana）的野外研究中，我们发现通过诱变手段对生物钟周期长度（clock period）造成显著扰动后，植株的存活率与繁殖力均会下降。通过将天然存在的等位基因进行基因组渐渗（genomic introgression）实现的更细微的生物钟调整实验表明，略长于24小时的生物钟周期具有适应性，这与此前描述生物过程时序在昼夜周期内适配程度的模型相符——该模型将此适配程度称为节律相位（phase）。 在分离重组自交系（segregating recombinant inbred lines, RILs）群体中，节律相位在整个生长季的不同月份间最大差异可达2小时，且生物钟周期与相位均表现出显著的遗传方差。包括发育速率、植株体量与坐果率在内的表现性状可通过主成分（principal components, PC）分析进行表征，且生物钟参数与第一主成分显著相关：在多个重组自交系群体中，略长于24小时的生物钟周期与更优的生长表现呈正相关。 本研究将受控环境下开展的生物钟行为功能分析拓展至自然环境，证实了节律相位的数量型变异对季节性变化的非生物因子具有极强响应性。本研究结果拓展了此前受控环境下的相关研究，证明了生物钟表型的离散型与数量型变异均与自然环境中的生长表现显著相关。