Evolutionary Genomics of Plant Adaptation and Speciation

重组在新物种的产生中起着核心作用。三种进化力量（选择、突变和遗传漂变）造成了种群之间的差异，而另外两种力量（基因流动和重组）使它们同质化。进化生物学家很早就认识到这种对抗，这导致许多人质疑，在不同种群之间交配缺乏地理障碍的情况下，物种形成的可能性。然而，近几十年来，基因流动的物种形成理论得到了理论和实证的支持。一个新出现的主题是抑制本地适应和/或生殖隔离的基因之间重组的机制的进化。在这里，我建议利用向日葵的基因组和种质资源来验证关于重组抑制因子的起源、建立和进化作用的基本假设。首先，我将研究多态性重组冷点的基因组基础。这将允许我测试关于不同重组抑制因子如何促进生态分化和物种形成的理论预测，以及探索常染色体上重组冷点与性染色体上的进化之间的相似之处。第二，我将确定建立这些区域的机制。基因流分化模型通常假设重组抑制的进化是为了减少局部适应等位基因之间的重组。然而，重组修饰因子（如染色体倒位）可能由于其他原因而传播，包括在倒位断点上的直接选择或由于小群体中的偶然事件（遗传漂变）。第三，我将寻找这些区域和导致个体优先与同一种群中的其他人交配的特征之间的联系（即，分类交配）。这种关联被预测为促进基因流动的物种形成。总之，这项工作将有助于确定重组抑制因子在植物适应和物种形成中的作用。此外，更好地了解向日葵的重组景观将有助于这一重要油料作物的育种计划。培训生态遗传学、基因组学和生物信息学方面的高素质人员将给加拿大带来额外的好处。

Recombination plays a central role in how new species arise. Three evolutionary forces (selection, mutation, and genetic drift) create differences between populations, while two other forces (gene flow and recombination) homogenize them. Evolutionary biologists have long recognized this antagonism, leading many to question the likelihood of speciation in the absence of geographic barriers to mating between diverging populations. However, in recent decades, speciation with gene flow has received both theoretical and empirical support. One emerging theme is the evolution of mechanisms that suppress recombination between genes underlying local adaptation and/or reproductive isolation. Here, I propose to leverage genomic and germplasm resources for sunflower to test fundamental hypotheses regarding the origin, establishment, and evolutionary role of recombination suppressors. First, I will investigate the genomic basis of polymorphic recombination cold spots. This will allow me to test theoretical predictions regarding how different recombination suppressors contribute to ecological divergence and speciation, as well as to explore parallels between the evolution of recombination cold spots on autosomes versus sex chromosomes. Second, I will determine the mechanisms by which such regions become established. Models of divergence with gene flow typically assume that recombination suppression evolves to reduce recombination between locally adapted alleles. However, recombination modifiers (e.g., chromosomal inversions) might spread for other reasons, including direct selection on inversion breakpoints or due to chance events in small populations (genetic drift). Third, I will search for associations between these regions and traits that cause individuals to preferentially mate with others in the same population (i.e., assortative mating). Such associations are predicted to facilitate speciation with gene flow. Overall, this work will help define the role of recombination suppressors in plant adaptation and speciation. Also, a better understanding of the recombination landscape in sunflower will facilitate breeding programs in this important oilseed crop. Additional benefits to Canada will accrue from the training of highly qualified personnel in ecological genetics, genomics, and bioinformatics.