PREMISE Due to climate change, more frequent and intense periodic droughts are predicted to increasingly pose major challenges to the persistence of plant populations. When a severe drought occurs over a broad geographical region, independent responses by individual populations provide replicated natural experiments for examining the evolution of drought resistance and the potential for evolutionary rescue. METHODS We used a resurrection approach to examine trait evolution in populations of the common monkeyflower, Mimulus guttatus, exposed to a record drought in California from 2011 to 2017. Specifically, we compared variation in traits related to drought escape and avoidance from seeds collected from 37 populations pre- and post-drought in a common garden. In a parallel experiment, we evaluated fitness in two populations, one which thrived and one which was nearly extirpated during the drought, under well-watered and dry-down conditions. RESULTS We observed substantial variation among populations in trait evolution. In the subset of populations where phenotypes changed significantly, divergence proceeded along trait correlations with some populations flowering rapidly with less vegetative tissue accumulation and others delaying flowering with greater vegetative tissue accumulation. The degree of trait evolution was only weakly correlated with drought intensity but strongly correlated with initial levels of standing variation. Fitness was higher in the post-drought than pre-drought accessions in both treatments for the thriving population, but lower in both treatments for the nearly extirpated population. CONCLUSIONS Together, our results indicate that evolutionary responses to drought are context dependent and reflect the standing genetic variation and genetic correlations present within populations.

中文翻译：

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对常见猴花（Mimulus guttatus）范围内历史性干旱的人口反应

前提 由于气候变化，预计更频繁和更强烈的周期性干旱将对植物种群的持久性构成越来越大的挑战。当在广阔的地理区域发生严重干旱时，个体种群的独立反应提供了重复的自然实验，用于检查抗旱性的进化和进化拯救的潜力。方法 我们使用复活方法来检查 2011 年至 2017 年在加利福尼亚遭受创纪录干旱的常见猴花（Mimulus guttatus）种群的性状进化。具体而言，我们比较了从 37 个种子收集的与干旱逃避和避免相关的性状变异公共花园中干旱前和干旱后的种群。在一个平行实验中，我们评估了两个群体的适应度，一种在干旱期间在充足的水和干涸的条件下茁壮成长，一种几乎灭绝。结果我们观察到在性状进化的人群中存在很大差异。在表型发生显着变化的种群子集中，分化沿着性状相关性进行，一些种群开花迅速，营养组织积累较少，而另一些种群开花延迟，营养组织积累较多。性状进化程度与干旱强度仅微弱相关，但与初始状态变异水平密切相关。对于繁荣种群的两种处理，干旱后的适应度高于干旱前的种质，但对于几乎灭绝的种群，两种处理的适应度都较低。结论 一起，