BACKGROUND Natural selection on fitness-related traits can be temporally heterogeneous among populations. As climate changes, understanding population-level responses is of scientific and practical importance. We examined 18 phenotypic traits associated with phenology, biomass, and ecophysiology in 403 individuals of natural Populus trichocarpa populations, growing in a common garden. RESULTS Compared with tree origin settings, propagules likely underwent drought exposures in the common garden due to significantly low rainfall during the years of measurement. All study traits showed population differentiation reflecting adaptive responses due to local genetic adaptation. Phenology and biomass traits were strongly under selection and showed plastic responses between years, co-varying with latitude. While phenological events (e.g., bud set and growth period) and biomass were under positive directional selection, post-bud set period, particularly from final bud set to the onset of leaf drop, was selected against. With one exception to water-use efficiency, ecophysiology traits were under negative directional selection. Moreover, extended phenological events jointly evolved with source niches under increased temperature and decreased rainfall exposures. High biomass coevolved with climatic niches of high temperature; low rainfall promoted high photosynthetic rates evolution. CONCLUSIONS This work underpins that P. trichocarpa is likely to experience increased fitness (height gain) by evolving toward extended bud set and growth period, abbreviated post-bud set period, and increased drought resistance, potentially constituting a powerful mechanism for long-lived tree species in surviving unpredictably environmental extremes (e.g., drought).

中文翻译：

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天然毛果杨种群的表型可塑性对普通花园中暂时环境变化的响应。

背景技术对适应度相关性状的自然选择在群体之间可能存在时间异质性。随着气候变化，了解人口层面的反应具有科学和实际意义。我们检查了生长在公共花园中的 403 个天然毛果杨种群个体的 18 个与物候、生物量和生态生理学相关的表型性状。结果与树木起源环境相比，由于测量年份降雨量显着偏低，繁殖体可能在普通花园中经历了干旱。所有研究特征均显示种群分化反映了由于局部遗传适应而产生的适应性反应。物候和生物量性状受到强烈选择，并在年份之间表现出可塑性响应，与纬度共同变化。虽然物候事件（例如，出芽和生长期）和生物量处于正向选择下，但出芽后时期，特别是从最终出芽到落叶开始的时间，却被选择了。除了水分利用效率之外，生态生理学特征都处于负向选择之下。此外，在温度升高和降雨量减少的情况下，延长的物候事件与源生态位共同演化。高生物量与高温气候生态位共同演化；低降雨量促进了高光合速率的进化。结论这项工作表明，毛果松​​很可能通过进化来延长花蕾和生长期、缩短花蕾后花期并增强抗旱性，从而提高适应性（高度增加），这可能构成长寿树的强大机制物种在不可预测的极端环境（例如干旱）中生存。