Data from: The genetic basis of speciation in the Giliopsis lineage of Ipomopsis (Polemoniaceae)

One of the most powerful drivers of speciation in plants is pollinator-mediated disruptive selection, which leads to the divergence of floral traits adapted to the morphology and behavior of different pollinators. Despite the widespread importance of this speciation mechanism, its genetic basis has been explored in only a few groups. Here, we characterize the genetic basis of pollinator-mediated divergence of two species in genus Ipomopsis, I. guttata and I. tenuifolia, using quantitative trait locus (QTL) analyses of floral traits and other variable phenotypes. We detected 1-6 QTLs per trait, with each QTL generally explaining small to modest amounts of the phenotypic variance of a backcross hybrid population. In contrast, flowering time and anthocyanin abundance (a metric of colour variation) were controlled by a few QTLs of relatively large effect. QTLs were strongly clustered within linkage groups, with 26 of 37 QTLs localized to six marker-interval "hotspots," all of which harbored pleiotropic QTLs. In contrast to other studies that have examined the genetic basis of pollinator shifts, our results indicate that, in general, mutations of small to modest effect on phenotype were involved. Thus, the evolutionary transition between the distinct pollination modes of I. guttata and I. tenuifolia likely proceeded incrementally, rather than saltationally.植物物种形成最强大的驱动因子之一，是传粉者介导的歧化选择——该选择可促使花部性状发生分化，以适配不同传粉者的形态与行为特征。尽管该物种形成机制的重要性已得到广泛认可，但目前仅在少数类群中对其遗传基础开展了相关探索。本研究以花旗杆属（Ipomopsis）的斑花旗杆（I. guttata）与细叶花旗杆（I. tenuifolia）为对象，通过对花部性状及其他可变表型开展数量性状基因座（quantitative trait locus, QTL）分析，解析了传粉者介导的物种分化的遗传基础。研究共在各性状中检测到1~6个QTL，且每个QTL通常仅能解释回交杂种群体中少量至中等程度的表型变异；与之相对，开花时间与花青素含量（花色变异的量化指标）则受少数效应量相对较大的QTL调控。QTL在连锁群中呈现显著的聚集现象：37个QTL中有26个定位于6个标记区间"热点区域"，且所有此类热点区域均包含多效性QTL。与其他针对传粉者转换遗传基础的研究不同，本研究结果表明，整体而言该分化过程涉及的是对表型效应量较小至中等的突变。因此，斑花旗杆与细叶花旗杆之间截然不同的传粉模式的演化过渡，大概率是以渐进式而非骤变式的方式完成的。