Genomic exploration of adaption and speciation in plant-insect interactions

面对基因流动，种群分化的发展和维持是进化生物学中长期存在的问题之一。我的团队最近的一个中性模型（CCV# 5）表明，自然分类的特征，如开花物候，协同距离隔离来放大种群遗传结构，即使在连续的景观上也是如此。这个有趣的结果是未来5年计划的大部分工作的出发点。我们将整合理论和基因组方法来描述物候在种群分化的起源和维持中的作用。基于个体和分析模型将探讨物候分类交配对群体遗传结构出现的贡献。实证研究的重点是黄花（Solidago spp.）与诱导瘿虫Eurosta solidaginis之间的相互作用。我们将采用基因组方法来研究反映生态物种形成早期阶段的两种不同的寄主植物转变。工作围绕三个基本主题进行组织。主题1。物候分类交配对种群分化的影响建模：这建立在我们的基本中性模型的基础上，该模型表明，当交配期的分类诱导物候隔离时，按距离隔离被强烈放大。我们将重点研究交配物候本身选择的空间异质性，以及物候QTL与其他性状在局部选择下连锁不平衡的发展。这种一般性的方法可以帮助我们理解空间排列与物候变异的相互作用，从而形成种群遗传结构，并应用于沿线进化和生态物种形成。主题2。植食性昆虫物种形成的物候学：当合子前分离性状的不同部分对抗均质化的基因流时，生态物种形成就会发生。这种不同的选择应该产生以促进生殖隔离的位点为中心的分化连锁群的“基因组岛”。发现基因组岛的研究并不总是确定它们是否集中在分化选择下的适应性/屏障位点上。我们将研究Eurosta的两种不同的寄主转移，一种发生在同栖植物中，另一种发生在同栖植物中，以确定基因组岛的长度不同，以及它们是否集中在影响昆虫羽化物候和/或寄主识别的位点上。主题3。胆囊大小和稳定选择的基因组证据：拟寄生虫和鸟类在黄菊花茎上的反平衡选择是稳定选择的典型例子。定量遗传学研究表明，胆囊大小的变化部分归因于昆虫的遗传变异，这可能部分归因于攻击的时间。基因型测序将定位胆囊大小的QTL，并确定等位基因频率是否在寄生蜂攻击时向一个方向移动，然后在鸟类攻击时反向移动。

The development and maintenance of population differentiation in the face of gene flow is one of the long-standing issues in evolutionary biology. A recent neutral model from my group (CCV# 5) shows that naturally assorting traits, like flowering phenology, synergize Isolation-by-Distance to amplify population genetic structure, even on a continuous landscape. This interesting result is the departure point for much of the work planned over the next 5 years. We will integrate theoretical and genomic approaches to delineate phenology's role in the origin and maintenance population differentiation. Individual-based and analytical models will probe the contribution of phenological assortative mating to the emergence of population genetic structure. Empirical work focuses on the interaction between goldenrod (Solidago spp.) and the gall-inducing insect, Eurosta solidaginis. We will take a genomic approach to examine two distinct hostplant shifts that reflect early stages of ecological speciation. Work is organized around three basic themes. Theme 1. Modeling the Impact of Phenological Assortative Mating on Population Differentiation: This builds on our basic neutral model showing that Isolation-by-Distance is strongly amplified when assortative for mating period induces Isolation-by-Phenology. We will focus on spatial heterogeneity in selection on mating phenology itself, and on the development of linkage disequilibrium between phenology QTL and loci for other traits under local selection. This general approach can inform our understanding the interaction of spatial arrangement with phenological variation to shape population genetic structure, with applications to evolution along clines and ecological speciation. Theme 2. Phenology in Speciation of Phytophagous Insects: Ecological speciation can occur when divergent section on prezygotic isolating traits counter homogenizing gene flow. This divergent selection should produce should "genomic islands" of differentiation-linkage groups cantered on loci promoting reproductive isolation. Studies finding genomic islands have not always determined if they center on adaptive/barrier loci under divergent selection. We will examine two distinct host-shifts by Eurosta, one occurring in sympatry and one in parapatry, to determine genomic islands differ in length, and if they center on loci affecting insect emergence phenology and/or host recognition. Theme 3. Gall Size and Genomic Evidence for Stabilizing Selection: The counter-balancing selection by parasitoids and birds on the goldenrod stem gallmaker is literally a textbook example of stabilizing selection. Quantitative genetic studies indicate the gall-size variation is in part attributable to insect genetic variation, which may in part be due to the timing of attack. Genotype-by-sequencing will locate QTL for gall size and determine if allele frequencies shift in one direction with parasitoid attack, then reverse with bird attack.