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，即一个物种分裂成两个物种，对于我们理解生物多样性和合理的保护政策至关重要。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的模型系统，在物种形成方面取得了重大发现。鉴于我们之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的研究。在接下来的五年里，我们将进行研究，以推进我们的长期研究目标：全面了解陆生脊椎动物，特别是长途候鸟的物种形成动态。我们的短期目标包括：******G1)深入分析季节性迁徙取向的遗传基础及其在物种形成中的作用。我们之前的工作表明，两种形式的斯温森画眉之间的杂交有中间的迁徙路线，这种行为似乎是由于4号染色体上一个特定基因组区域的变异。我们将使用两种形式的莺之间的杂交区（和迁徙分界线）进行更深入的研究。******G2)测试是否有特定的基因组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。这个新发展的观点，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是一致的，与现有的关于物种之间哪些区域会发生差异的理论有很大的不同。******G3)检查两种不同类型的遗传物质：线粒体DNA和核DNA之间是否存在共同进化。如果是这样的话，这种共同进化会导致杂交后代的适应度降低，并促进物种形成。******G4)确定物种形成过程中基因组分化模式是否在亲缘关系较近的物种群（例如两种莺）与亲缘关系较远的物种群（例如莺与啄木鸟）之间更为相似。这样的模式将指向特定群体中物种形成的共同原因，并将表明物种形成本身可以被视为随着时间的推移而进化的东西。******G5)杂交带理论的发展及其在物种保护中的应用。许多物种与其他物种杂交，但关于杂交对物种概念和保护政策的影响尚未达成共识。我们将通过扩展杂交带理论，并对杂交带间基因组分化的经验模式及其对有效保护的意义进行综述，为达成共识做出贡献。

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.