Genetics of Differences Between the Mating Systems of Mimulus guttatus and M. nasutus

9727578 Willis数量性状基因座(QTL)的识别和分析为直接评估干扰生物进化差异的遗传基础提供了一个强大的工具。植物中的一个进化转变为解决适应的遗传基础提供了一个独特的机会，那就是异交自交受精的进化，这可能是被子植物中最常见的进化转变。玄参属(Scrophulariaceae)中有许多密切相关和相互干扰的物种或种群，为研究自交受精和物种形成的进化提供了一个很好的模式系统。滴状寄生植物复合体中常见的黄色猴花可以说是该属中最多型性和进化最快的成员，种群在自交受精程度方面差异极大。拟议的研究有两个具体目标。首先，我们建议对主要异交的滴虫种群和高度自交的种群之间的花差异进行彻底的遗传分析，以确定是否有大效应基因导致这两个物种之间的极端花差异。这一目标将通过利用基于微卫星、AFLP和RAPD标记的微卫星基因组高分辨率连锁图谱来定位影响花形态的数量性状基因座来实现。其次，我们建议检验影响与自交相关的花卉性状的数量性状基因座是否确实对自然种群的自交率有直接影响。这一目标将通过在田间分析导入系的自交率来实现，这些导入系含有一对斑潜蝇背景中的花QTL的等位基因。这些实验将解决长期存在的基本问题，即突变在适应进化中的重要影响。例如，新达尔文进化论的一个基本主张是，自然选择作用于种群中个体之间非常微小的表型差异。如果这种微妙的个体差异有遗传成分，那么适应将产生于对小作用基因的稳定固定。相反，其他人则认为，适应往往是极少数基因位点剧烈变化的结果。这些实验将有助于回答这样的基本问题。它们还将有助于我们对自交和其他形式的近亲交配如何以及为什么在自然和驯化的动植物种群中进化的基本理解。

9727578 Willis The identification and analysis of quantitative trait loci (QTLs) offers a powerful tool with which to assess directly the genetic basis of evolved differences between interfertile organisms. One evolutionary transition in plants that offers a unique opportunity to address the genetic basis of adaptations is the evolution of self-fertilization from outcrossing, which is perhaps the most frequent evolutionary transition in angiosperms. The genus Mimulus (Scrophulariaceae), within which are many closely related and interfertile species or populations, provides an excellent model system for studying the evolution of self-fertilization and speciation. The common yellow monkeyflowers in the Mimulus guttatus species complex are arguably the most polytypic and most rapidly evolving members of the genus, and populations vary tremendously in terms of the degree of self-fertilization. There are two specific goals of the proposed study. First, we propose to conduct a thorough genetic analysis of the floral differences between a primarily outcrossing population of Mimulus guttatus and a highly selfing population of Mimulus nasutus in order to determine whether genes of large effect contribute to the extreme floral differences between these species. This goal will be accomplished through the mapping of quantitative trait loci affecting floral morphology using a high-resolution linkage map of the Mimulus genome based on microsatellite, AFLP, and RAPD markers. Second, we propose to test whether quantitative trait loci affecting floral traits that are correlated with selfing actually have direct effects on the rate of self-fertilization in a natural population. This goal will be accomplished by analyzing in the field the selfing rates of introgression lines containing a M. nasutus allele for floral QTLs in a M. guttatus background. These experiments will address long-standing and fundamental questions about the role of mutations of large effect on the evolution of adaptations. For example, a fundamental claim of neo-Darwinian evolution is that natural selection acts on very slight phenotypic differences among individuals in a population. If this subtle individual variation has a genetic component, then adaptations will result from the steady fixation of genes of small effect. Conversely, others have argued that adaptation frequently results from drastic changes at a very few genetic loci. These experiments will help to answer basic questions such as this. They will also contribute to our basic understanding of how and why self-fertilization and other forms of inbreeding evolve in natural and domesticated populations of plants and animals.