Data from: Bud phenology and growth are subject to divergent selection across a latitudinal gradient in Populus angustifolia and impact adaptation across the distributional range and associated arthropods

Temperate forest tree species that span large geographical areas and climatic gradients often have high levels of genetic variation. Such species are ideal for testing how neutral demographic factors and climate-driven selection structure genetic variation within species, and how this genetic variation can affect ecological communities. Here, we quantified genetic variation in vegetative phenology and growth traits in narrowleaf cottonwood, Populus angustifolia, using three common gardens planted with genotypes originating from source populations spanning the species' range along the Rocky Mountains of North America (ca. 1700 km). We present three main findings. First, we found strong evidence of divergent selection (QST > FST) on fall phenology (bud set) with adaptive consequences for frost avoidance. We also found evidence for selection on bud flush duration, tree height, and basal diameter, resulting in population differentiation. Second, we found strong associations with climate variables that were strongly correlated with latitude of origin. More strongly differentiated traits also showed stronger climate correlations, which emphasizes the role that climate has played in divergent selection throughout the range. We found population × garden interaction effects; for some traits, this accounted for more of the variance than either factor alone. Tree height was influenced by the difference in climate of the source and garden locations and declined with increasing transfer distance. Third, growth traits were correlated with dependent arthropod community diversity metrics. Synthesis. Overall, we conclude that climate has influenced genetic variation and structure in phenology and growth traits and leads to local adaptation in P. angustifolia, which can then impact dependent arthropod species. Importantly, relocation of genotypes far northward or southward often resulted in poor growth, likely due to a phenological mismatch with photoperiod, the proximate cue for fall growth cessation. Genotypes moved too far southward suffer from early growth cessation, whereas those moved too far northward are prone to fall frost and winter dieback. In the face of current and forecasted climate change, habitat restoration, forestry, and tree breeding efforts should utilize these findings to better match latitudinal and climatic source environments with management locations for optimal future outcomes.

分布于广阔地理范围与气候梯度的温带林木树种，通常具备高水平的遗传变异。这类物种是检验中性种群动态因子与气候驱动选择如何塑造物种内遗传变异，以及该遗传变异如何影响生态群落的理想研究对象。
本研究以窄叶杨（Populus angustifolia）为研究材料，利用3处同质园（common garden）试验场地，对源自覆盖其北美落基山脉分布范围（约1700公里）的源种群的基因型展开分析，量化其营养物候与生长性状的遗传变异。本研究得到三项核心结论：
其一，我们发现秋季物候（芽封顶）存在显著的歧化选择证据（QST > FST），该选择对避霜具有适应性意义；同时观测到芽萌动时长、树高与基径受到选择作用，进而导致种群分化。
其二，我们发现气候变量与源种群的起源纬度存在极强相关性；性状分化程度越高，其与气候的关联度也越强，这凸显了气候在整个分布范围内对歧化选择的驱动作用。本研究还观测到种群×试验场地的交互效应，对于部分性状而言，该交互效应解释的变异量远超单一因子的单独贡献。树高受源种群与试验场地的气候差异影响，且随引种距离的增加而显著降低。
其三，生长性状与依赖该树种的节肢动物群落多样性指标存在显著相关性。
综上，本研究认为气候塑造了窄叶杨物候与生长性状的遗传变异及结构，并促使其产生本地适应，进而对依赖该树种的节肢动物类群产生影响。
值得注意的是，将基因型向极北或极南方向大范围移栽，通常会导致生长不良，这可能源于物候与光周期（photoperiod）的不匹配——光周期是调控秋季生长停止的直接信号。向南方移栽过远的基因型会出现生长过早停止，而向北方移栽过远的基因型则易遭受秋季霜冻与冬季枯梢。
面对当前及预测中的气候变化，生境修复、林业经营与林木育种工作应借鉴本研究结论，更好地匹配源种群的纬度与气候环境与管理选址，以实现最优的未来经营效果。