Local adaptation is common in plants, yet characterization of its underlying genetic basis is rare in herbaceous perennials. Moreover, while many plant species exhibit intraspecific chemical defence polymorphisms, their importance for local adaptation remains poorly understood. We examined the genetic architecture of local adaptation in a perennial, obligately-outcrossing herbaceous legume, white clover (Trifolium repens). This widespread species displays a well-studied chemical defence polymorphism for cyanogenesis (HCN release following tissue damage) and has evolved climate-associated cyanogenesis clines throughout its range. Two biparental F₂ mapping populations, derived from three parents collected in environments spanning the U.S. latitudinal species range (Duluth, MN, St. Louis, MO and Gainesville, FL), were grown in triplicate for two years in reciprocal common garden experiments in the parental environments (6,012 total plants). Vegetative growth and reproductive fitness traits displayed trade-offs across reciprocal environments, indicating local adaptation. Genetic mapping of fitness traits revealed a genetic architecture characterized by allelic trade-offs between environments, with 100% and 80% of fitness QTL in the two mapping populations showing significant QTL×E interactions, consistent with antagonistic pleiotropy. Across the genome there were three hotspots of QTL colocalization. Unexpectedly, we found little evidence that the cyanogenesis polymorphism contributes to local adaptation. Instead, divergent life history strategies in reciprocal environments were major fitness determinants: selection favoured early investment in flowering at the cost of multiyear survival in the southernmost site versus delayed flowering and multiyear persistence in the northern environments. Our findings demonstrate that multilocus genetic trade-offs contribute to contrasting life history characteristics that allow for local adaptation in this outcrossing herbaceous perennial.

中文翻译：

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遗传权衡是白三叶草局部适应不同生活史策略的基础

局部适应在植物中很常见，但对其潜在遗传基础的表征在多年生草本植物中很少见。此外，虽然许多植物物种表现出种内化学防御多态性，但它们对局部适应的重要性仍然知之甚少。我们检查了多年生、专性异交的草本豆科植物白三叶草 ( Trifolium repens )中局部适应的遗传结构。这种广泛分布的物种显示出一种经过充分研究的生氰化学防御多态性（组织损伤后释放 HCN），并在其整个范围内进化出与气候相关的生氰系。两个双亲 F ₂ 来自美国纬度物种范围（明尼苏达州德卢斯，密苏里州圣路易斯和佛罗里达州盖恩斯维尔）环境中收集的三个亲本的绘图种群在亲本环境中的互惠公共花园实验中一式三份生长两年（6,012总植物）。营养生长和生殖健康特征在相互环境中表现出权衡，表明局部适应。适应度性状的遗传作图揭示了一种以环境之间等位基因权衡为特征的遗传结构，两个作图群体中 100% 和 80% 的适应度 QTL 显示出显着的 QTL×E 相互作用，与拮抗性多效性一致。在整个基因组中，存在三个 QTL 共定位热点。不料，我们几乎没有发现发氰多态性有助于局部适应的证据。相反，互惠环境中不同的生活史策略是主要的适应性决定因素：选择有利于在最南端以多年生存为代价对开花进行早期投资，而不是在北部环境中延迟开花和多年持续存在。我们的研究结果表明，多位点遗传权衡有助于对比生活史特征，从而允许在这种异交多年生草本植物中进行局部适应。选择有利于在最南端以多年生存为代价对开花进行早期投资，而不是在北部环境中延迟开花和多年持续存在。我们的研究结果表明，多位点遗传权衡有助于对比生活史特征，从而允许在这种异交多年生草本植物中进行局部适应。选择有利于在最南端以多年生存为代价对开花进行早期投资，而不是在北部环境中延迟开花和多年持续存在。我们的研究结果表明，多位点遗传权衡有助于对比生活史特征，从而允许在这种异交多年生草本植物中进行局部适应。