Museum of Vertebrate Zoology, University of California, Berkeley, 3101 Valley Life Sciences Building, CA, 94720-3160, USA.
Mol Ecol. 2016 Nov;25(22):5605-5607. doi: 10.1111/mec.13869.
Identifying the individual loci and mutations that underlie adaptation to extreme environments has long been a goal of evolutionary biology. However, finding the genes that underlie adaptive traits is difficult for several reasons. First, because many traits and genes evolve simultaneously as populations diverge, it is difficult to disentangle adaptation from neutral demographic processes. Second, finding the individual loci involved in any trait is challenging given the respective limitations of quantitative and population genetic methods. In this issue of Molecular Ecology, Hendrick et al. (2016) overcome these difficulties and determine the genetic basis of microgeographic adaptation between geothermal vent and nonthermal populations of Mimulus guttatus in Yellowstone National Park. The authors accomplish this by combining population and quantitative genetic techniques, a powerful, but labour-intensive, strategy for identifying individual causative adaptive loci that few studies have used (Stinchcombe & Hoekstra ). In a previous common garden experiment (Lekberg et al. 2012), thermal M. guttatus populations were found to differ from their closely related nonthermal neighbours in various adaptive phenotypes including trichome density. Hendrick et al. (2016) combine quantitative trait loci (QTL) mapping, population genomic scans for selection and admixture mapping to identify a single genetic locus underlying differences in trichome density between thermal and nonthermal M. guttatus. The candidate gene, R2R3 MYB, is homologous to genes involved in trichome development across flowering plants. The major trichome QTL, Tr14, is also involved in trichome density differences in an independent M. guttatus population comparison (Holeski et al. 2010) making this an example of parallel genetic evolution.
长期以来，确定导致生物适应极端环境的个体基因和突变一直是进化生物学的目标。然而，由于许多特征和基因在种群分化的同时进化，因此很难将适应与中性的种群动态过程区分开来。其次，由于数量遗传学和群体遗传学方法各自的局限性，找到任何特征涉及的单个基因座都具有挑战性。在本期《分子生态学》中，Hendrick 等人（2016 年）克服了这些困难，并确定了黄石国家公园中温泉和非温泉 Mimulus guttatus 微地理适应的遗传基础。作者通过结合群体遗传学和数量遗传学技术来实现这一目标，这是一种强大但劳动强度大的策略，可用于确定很少有研究使用的个体因果适应性基因座（Stinchcombe & Hoekstra ）。在之前的一个共同田间实验中（Lekberg 等人，2012 年），发现热敏 Mimulus guttatus 种群与其亲缘关系密切的非热敏邻域在各种适应性表型上存在差异，包括毛状体密度。Hendrick 等人（2016 年）结合数量性状基因座（QTL）作图、群体基因组选择扫描和杂交作图，鉴定了一个单一的遗传基因座，该基因座与热敏和非热敏 Mimulus guttatus 之间毛状体密度的差异有关。候选基因 R2R3 MYB 与开花植物中毛状体发育有关的基因同源。主要的毛状体 QTL Tr14 也参与了独立的 Mimulus guttatus 种群比较中的毛状体密度差异（Holeski 等人，2010 年），这是平行遗传进化的一个例子。
