Data from: Admixture mapping of male nuptial color and body shape in a recently formed hybrid population of threespine stickleback

Despite recent progress, we still know relatively little about the genetic architecture that underlies adaptation to divergent environments. Determining whether the genetic architecture of phenotypic adaptation follows any predictable patterns requires data from a wide variety of species. However, in many organisms, genetic studies are hindered by the inability to perform genetic crosses in the laboratory or by long generation times. Admixture mapping is an approach that circumvents these issues by taking advantage of hybridization that occurs between populations or species in the wild. Here, we demonstrate the utility of admixture mapping in a naturally occurring hybrid population of threespine sticklebacks (Gasterosteus aculeatus) from Enos Lake, British Columbia. Until recently, this lake contained two species of sticklebacks adapted to divergent habitats within the lake. This benthic-limnetic species pair diverged in a number of phenotypes, including male nuptial coloration and body shape, which were previously shown to contribute to reproductive isolation between them. However, recent ecological disturbance has contributed to extensive hybridization between the species, and there is now a single, admixed population within Enos Lake. We collected over 500 males from Enos Lake and found that most had intermediate nuptial color and body shape. By genotyping males with nuptial color at the two extremes of the phenotypic distribution, we identified seven genomic regions on three chromosomes associated with divergence in male nuptial color. These genomic regions are also associated with variation in body shape, suggesting that tight linkage and/or pleiotropy facilitated adaptation to divergent environments in this benthic-limnetic species pairs.

尽管近年来相关研究已取得一定进展，但我们对驱动生物适应异质环境的遗传架构（genetic architecture）仍所知有限。若要阐明表型适应的遗传架构是否存在可预测的模式，需获取多样物种的相关研究数据。然而，对多数生物而言，遗传研究常受限于无法在实验室开展遗传杂交，或是世代周期过长的问题。混合图谱定位（admixture mapping）作为一种研究策略，可通过利用野生种群或物种间自然发生的杂交事件，规避上述研究障碍。本研究以加拿大不列颠哥伦比亚省埃诺斯湖（Enos Lake）的自然杂交三刺鱼（threespine sticklebacks，*Gasterosteus aculeatus*）种群为研究对象，验证了混合图谱定位方法的实用性。直至近年，该湖曾栖息着两种适应湖内不同生境的刺鱼。这对底栖-浮游型物种在诸多表型上存在分化，包括雄性婚色与体型，此前已有研究证实这些表型差异促成了二者的生殖隔离。然而，近期的生态扰动导致这两个物种间发生了广泛杂交，如今埃诺斯湖内仅存一个混合种群。我们从埃诺斯湖采集了500余尾雄性刺鱼，发现其中多数个体的雄性婚色与体型均呈中间型。通过对表型分布两端（即婚色极端值）的雄性个体进行基因分型，我们在3条染色体上鉴定出7个与雄性婚色分化相关的基因组区域。这些基因组区域同时与体型变异相关，这表明紧密连锁或（和）多效性（pleiotropy）推动了这对底栖-浮游型物种对异质环境的适应。