Data from: Adaptive differentiation in floral traits in the presence of high gene flow in scarlet gilia (Ipomopsis aggregata)

Plant-pollinator interactions are thought to be major drivers of floral trait diversity. However, the relative importance of divergent pollinator-mediated selection versus neutral processes in floral character evolution has rarely been explored. We tested for adaptive floral trait evolution by comparing differentiation at neutral genetic loci to differentiation at quantitative floral traits in a putative Ipomopsis aggregata hybrid zone. Typical I. aggregata subsp. candida displays slender white tubular flowers that are typical of flowers pollinated by hawkmoths and subsp. collina displays robust red tubular flowers typical of flowers pollinated by hummingbirds; yet hybrid flower morphs are abundant across the East Slope of the Colorado Rockies. We estimated genetic differentiation (FST) for nuclear and chloroplast microsatellite loci and used a half-sib design to calculate quantitative trait divergence (QST) from collection sites across the morphological hybrid zone. We found little evidence for population structure and estimated mean FST to be 0.032. QST values for several floral traits including corolla tube length and width, color, and nectar volume were large and significantly greater than mean FST. We performed multivariate comparisons of neutral loci to genetic correlations within and between populations and found a strong signal for divergent selection, suggesting that specific combinations of floral display and reward traits may be the targets of selection. Our results show little support for historical subspecies categories, yet floral traits are more diverged than expected due to drift alone. Non-neutral divergence for multivariate quantitative traits suggests that selection by pollinators is maintaining a correlation between display and reward traits.

植物-传粉者互作被普遍认为是花部性状多样性形成的核心驱动因子。然而，传粉者介导的歧化选择与中性演化过程在花部性状演化中的相对重要性，迄今仍鲜有研究探讨。
本研究针对推测的聚花福禄考（Ipomopsis aggregata）杂交带，通过对比中性遗传位点的分化程度与数量花部性状的分化水平，检验适应性花部性状演化机制。典型的聚花福禄考白花亚种（I. aggregata subsp. candida）具有细长白色管状花，契合天蛾传粉的花部特征；而红花亚种（I. aggregata subsp. collina）则具粗壮红色管状花，典型适配蜂鸟传粉。但在科罗拉多落基山脉东坡，各类杂交花形态却广泛分布。
我们对核微卫星位点与叶绿体微卫星位点开展了遗传分化系数（FST）估算，并采用半同胞设计，基于形态杂交带内的多个采样点计算了数量性状分化（quantitative trait divergence, QST）。研究未检测到显著的种群遗传结构，估算的平均FST为0.032。
包括花冠管长宽、花色以及花蜜体积在内的多个花部性状，其QST值均较高，且显著高于平均FST。我们进一步对中性位点与种群内、种群间的遗传相关性开展多变量对比，发现了强烈的歧化选择信号，表明花部展示与奖励性状的特定组合可能为选择靶标。
本研究结果几乎不支持传统的亚种分类，但花部性状的分化程度远超仅由遗传漂变预期的水平。多变量数量性状的非中性分化表明，传粉者介导的选择维持了花部展示与奖励性状之间的相关性。