Evolution of the causes of speciation: comparative analysis of genomic variation and the genetic basis of traits responsible for diversification

了解物种形成，一个物种分裂成两个，是我们理解生物多样性和健全的保护政策的关键。我的研究小组利用加拿大西部以及北美和欧亚大陆其他地区的鸟类和蝾螈模型系统，在物种形成方面取得了重要发现。鉴于我们先前对各种物种复合体（即密切相关的物种或亚种在相遇时杂交的群体）的研究，我们现在已经准备好对基因组进化模式（即DNA的变化）与种群间性状分化和生殖隔离模式之间的关系进行开创性研究。在接下来的五年里，我们将开展研究，推进我们的长期研究目标：发展对陆栖脊椎动物，特别是长距离候鸟物种形成动态的全面了解。我们的短期目标包括：**G1）对季节性迁徙取向的遗传基础及其在物种形成中的作用进行深入分析。我们以前的工作表明，两种形式的斯温森画眉之间的杂交有中间迁移路线，这种行为似乎是由于在染色体4上的一个特定的基因组区域的变化。我们将使用两种莺之间的杂交区（和迁徙分界线）更深入地研究这一点。**G2）测试是否存在特定的基因组区域，这些区域在群体之间分化之前倾向于在整个物种复合体中传播。这个新发展的想法，我们称之为“分化前的扫描”，与至少两个正在研究的物种群体的证据一致，并且与现有的关于物种之间哪些区域变得不同的理论截然不同。G3）检查两种不同类型的遗传物质之间是否存在协同进化：线粒体DNA和核DNA。如果是这样的话，这种共同进化可能会导致杂交后代的适应度较低，并有助于物种形成。**G4）确定物种形成过程中的基因组分化模式是否在密切相关的物种组之间（例如两个物种组的莺）更相似，而不是更远的物种组（例如莺与啄木鸟）。这种模式将指出某些群体内物种形成的共同原因，并表明物种形成本身可以被视为随着时间的推移而演变的东西。G5）发展杂交带理论及其在物种保护中的应用。许多物种与其他物种杂交，但没有关于杂交的物种概念和保护政策的影响达成共识。我们将有助于扩大杂交区理论和跨杂交区的基因组分化的经验模式及其对有效保护的影响进行审查的共识。

Understanding speciation, the splitting of one species into two, is essential for our understanding of biodiversity and sound conservation policy. My research group has made key discoveries regarding speciation, using model systems of birds and salamanders of western Canada as well as other regions of North America and Eurasia. Given our prior research on a variety of species complexes (i.e. groups of closely related species or subspecies that hybridize where they meet), we are now well poised to conduct pioneering research on the relationship between patterns of genomic evolution (i.e. changes in DNA) and patterns of trait differentiation and reproductive isolation among populations. During the next five years, we will conduct research that advances our long-term research goal: developing a comprehensive understanding of the dynamics of speciation in land-dwelling vertebrates, especially within long-distance migratory birds. Our short-term goals include:******G1) Conducting in-depth analysis of the genetic basis of seasonal migratory orientation and its role in speciation. Our previous work showed that hybrids between two forms of Swainson's thrush have intermediate migratory routes and that this behavior appears to be due to variation in a particular genomic region on chromosome 4. We will investigate this in more depth using a hybrid zone (and migratory divide) between two forms of warblers. ******G2) Testing whether there are specific genomic regions that tend to spread throughout species complexes before becoming differentiated between groups. This newly developed idea, which we call “sweep before differentiation,” is consistent with evidence in at least two species groups under examination, and differs dramatically from existing theories for what regions become different between species.******G3) Examining whether there is coevolution between two distinct types of genetic material: mitochondrial DNA and nuclear DNA. If so, such coevolution can cause low fitness in hybrids and contribute to speciation. ******G4) Determining whether patterns of genomic differentiation during speciation tend to be more similar between species groups that are closely related (e.g. two species groups of warblers), in contrast to more distantly related species groups (e.g. warblers versus woodpeckers). Such a pattern would point to common causes of speciation within certain groups, and would show that speciation itself can be viewed as something that evolves over time.******G5) Developing hybrid zone theory and its application to species conservation. Many species hybridize with other species, yet there is not consensus regarding the implications of hybridization for species concepts and conservation policy. We will contribute to a consensus by expanding hybrid zone theory and conducting a review of empirical patterns of genomic differentiation across hybrid zones and their implications for effective conservation.