Comparative genomic analysis of hybridization and speciation: uncovering genes and traits responsible for diversification

有大量证据表明物种形成过程，即一个物种进化成两个物种，但推动这一过程的选择性力量仍存在很大争议。杂交区是不同但相关物种在一定程度上接触和杂交的区域，为确定哪些性状与物种形成关系最密切提供了极好的机会。加拿大西部有许多不同的西部和东部鸟类之间的杂交地带，在冰河时代，当它们被分开在不同的南部地区时，它们进化出了差异。在许多不同的杂交区，我们将研究各种性状的变异，确定哪些性状在每个区表现出最大的变化；这些可能是与物种形成最相关的性状。我们还将使用最近开发的一种称为下一代DNA测序的遗传分析方法来识别与感兴趣的特征相关的基因。为了了解这些基因在基因组中的位置(例如，在什么染色体上)，我们将使用下一代测序为每个杂交区组装一个参考个体的基因组。一个重要的特征是季节性迁徙。许多西方和东方物种在从繁殖地到越冬地的路线上有很大的不同。我们假设混血儿有中间的迁徙倾向，因此存活率较低。我们将使用跟踪设备和定向笼子来确定每个杂交区鸟类的定向行为，并将确定与迁徙差异相关的遗传区域。我们的工作还将(1)使用基因组分析来重建几个物种的历史，这些物种可能是通过其他物种的杂交而产生的，以及(2)测试是否存在某些关键的基因组区域，例如性染色体，在鸟类的物种形成中发挥重要作用。通过在六组杂交物种中产生组装的基因组和基因-性状关联研究，我们将为未来适应和物种形成的遗传基础的研究贡献更多的知识。

There is abundant evidence for the process of speciation, whereby a single species evolves into two, but the selective forces that drive this process are under much debate. Hybrid zones, regions where different but related species come into contact and interbreed to some extent, provide excellent opportunities to determine which traits are most involved in speciation. Western Canada has many hybrid zones between distinct western and eastern forms of birds that evolved differences while they were separated in different southern regions during the Ice Ages. Across a number of different hybrid zones, we will study variation in a variety of traits, determining which traits show the sharpest change across each zone; these are likely the traits most involved in speciation. We will also use a recently developed method of genetic analysis called next-generation DNA sequencing to identify genes associated with traits of interest. To understand the location of these genes in the genome (e.g., on what chromosome), we will use next-generation sequencing to assemble the genome of one reference individual for each hybrid zone. One important trait is seasonal migration. Many pairs of western and eastern species differ dramatically in the routes that they take from their breeding ranges to their wintering ranges. We hypothesize that hybrids have intermediate migratory orientations and suffer lower survival as a result. We will determine orientation behavior of birds in each hybrid zone using tracking devices and orientation cages, and will determine the genetic regions associated with differences in migration. Our work will also (1) use genomic analysis to reconstruct the history of several species that may have arisen through hybridization of other species, and (2) test whether there are certain key genomic regions, such as the sex chromosomes, that play a strong role in speciation within birds. By generating assembled genomes and gene-trait association studies in six groups of hybridizing species, we will contribute much knowledge toward future studies of the genetic basis of adaptation and speciation.