Data from: Growth gains from selective breeding in a spruce hybrid zone do not compromise local adaptation to climate

Hybrid zones contain extensive standing genetic variation that facilitates rapid responses to selection. The Picea glauca x P. engelmannii hybrid zone in western Canada is the focus of tree breeding programs that annually produce ~90 million reforestation seedlings. Understanding the direct and indirect effects of selective breeding on adaptive variation is necessary to implement assisted gene flow polices in Alberta and British Columbia that match these seedlings with future climates. We decomposed relationships among hybrid ancestry, adaptive traits and climate to understand the implications of selective breeding for climate adaptations and assisted gene flow strategies. The effects of selection on associations among hybrid index estimated from ~6500 SNPs, adaptive traits, and provenance climates were assessed for ~2400 common garden seedlings. Hybrid index differences between natural and selected seedlings within breeding zones were small in Alberta (average +2%), but larger and more variable in BC (average -7 %, range -24% to +1%), slightly favoring P. glauca ancestry. The average height growth gain of selected seedlings over natural seedlings within breeding zones was 36% (range 12% to 86%). Clines in growth with temperature-related variables were strong, but differed little between selected and natural populations. Seedling hybrid index and growth trait associations with evapotranspiration-related climate variables were stronger in selected than in natural seedlings, indicating possible pre-adaptation to drier future climates. Associations among cold hardiness, hybrid ancestry and cold-related climate variables dominated signals of local adaptation that were preserved in breeding populations. Strong hybrid ancestry-phenotype-climate associations suggest that assisted gene flow will be necessary to match interior spruce breeding populations with shifting future climates. The absence of antagonistic selection responses among traits and maintenance of cold adaptation in selected seedlings suggests breeding populations can be safely redeployed using assisted gene flow prescriptions similar to those of natural populations.杂交带（hybrid zone）蕴藏着丰富的现存遗传变异，可促进群体对选择产生快速响应。加拿大西部的白云杉（*Picea glauca*）×恩格尔曼云杉（*Picea engelmannii*）杂交带，是每年培育约9000万株造林苗木的林木育种项目的核心研究对象。明晰选择性育种对适应性变异的直接与间接效应，是加拿大阿尔伯塔省与不列颠哥伦比亚省（British Columbia, BC）实施辅助基因流（assisted gene flow）政策的必要前提——该政策旨在使造林苗木适配未来气候环境。本研究解析了杂交祖先比例、适应性性状与气候之间的关联，以明确选择性育种对气候适应性及辅助基因流策略的影响。本研究针对约2400株共育园（common garden）苗木，评估了选择对基于约6500个单核苷酸多态性（single nucleotide polymorphisms, SNPs）估算的杂交指数、适应性性状与种源气候之间关联的影响。育种区内天然苗木与选育苗木的杂交指数差异在阿尔伯塔省较小（平均+2%），但在不列颠哥伦比亚省（BC）更大且变异程度更高（平均-7%，波动范围-24%至+1%），整体略微偏向白云杉祖先。育种区内选育苗木相较于天然苗木的平均树高生长增益达36%（波动范围12%至86%）。生长性状与温度相关变量的渐变群（cline）特征显著，但选育种群与天然种群之间的该特征差异极小。选育苗木的杂交指数与生长性状同蒸散（evapotranspiration）相关气候变量的关联强度，高于天然苗木，这表明选育种群可能已预适应未来更为干旱的气候环境。抗寒性、杂交祖先比例与低温相关气候变量之间的关联，构成了育种种群中得以保留的本地适应性核心信号。显著的杂交祖先比例-表型-气候关联表明，为使内陆云杉育种种群适配未来不断变化的气候，辅助基因流手段必不可少。性状间未出现拮抗选择效应，且选育苗木保留了抗寒性，这表明可采用与天然种群类似的辅助基因流方案，安全地重新部署育种种群。