Testing mechanisms of speciation and hybridization in terrestrial vertebrates

有大量证据表明物种形成的过程，即一个物种进化成两个物种，但通常推动这一过程的力量是有争议的。一些人提出，物种间生殖隔离的进化是由对不同栖息地的适应推动的。其他人则提出，生殖隔离是性选择推动物种内持续变化的结果，导致它们接触时不相容。我们将通过比较加拿大西部和西伯利亚中部不同物种对的特征差异和生殖隔离模式来测试这些想法。这两个地区在冰河时代都没有森林。现在，每种鸟都有许多不同的东西方鸟类之间的接触区，这些鸟在不同的避难所中分道扬镳。这些接触区为研究新物种是如何产生的提供了“天然实验室”。我们的目标是研究生殖隔离是否以及如何在这些地区的多个物种对中发展，然后得出关于促进或阻碍物种形成的因素的一般性结论。我们将研究遗传、歌唱、生态、迁徙行为、体型和体型的地理变异，目的是测量生殖隔离及其原因。除了帮助解决有性选择和自然选择在物种形成中的相对重要性外，这些研究还将检查(1)杂交和(2)季节性迁徙行为在物种形成中的重要性。为了检查杂交，我们将比较三个鸣禽杂交区，并确定是否有基因组的共同部分在选择。我们还将测试奥杜邦林莺是否是已知的第一个鸟类杂交物种形成案例；初步数据表明是这样的。为了研究季节性迁徙行为，我们将研究两种类型的斯文森画眉之间杂交区域的迁徙行为的变化；我们假设纯类型的画眉会有不同的迁徙路线，而杂交画眉会有中间的路线，并将遭受更高的死亡率。鸟类中有许多已知的迁徙分化，我们的研究将首次直接测试由于迁徙行为较差而选择杂交种的想法。

There is abundant evidence for the process of speciation, whereby a single species evolves into two, but the forces that usually drive this process are controversial. Some propose that the evolution of reproductive isolation between species is driven by adaptation to differing habitats. Others propose that reproductive isolation evolves as a result of sexual selection driving continual change within species, resulting in incompatibilities when they come into contact. We will test these ideas by comparing patterns of trait divergence and reproductive isolation in a variety of species pairs in western Canada and central Siberia. Both regions were not forested during the Ice Ages. Now, each contains many contact zones between distinct western and eastern forms of birds that diverged in separate refugia. These contact zones provide a 'natural laboratory' for the study of how new species arise. Our goal is to study whether and how reproductive isolation is developing in multiple species pairs in these regions, and then to draw general conclusions regarding the factors that promote or hinder speciation. We will study geographic variation in genetics, songs, ecology, migratory behavior, and body shape and size with the goal of measuring reproductive isolation and its causes. In addition to helping resolve the relative importance of sexual and natural selection in speciation, these studies will examine the importance of (1) hybridization and (2) seasonal migratory behavior in speciation. To examine hybridization, we will compare three warbler hybrid zones and determine whether there are common parts of the genome under selection. We will also test whether the Audubon's warbler is the first known case of hybrid speciation in birds; preliminary data suggest it is. To examine seasonal migratory behavior, we will study variation in migratory behavior across a hybrid zone between two forms of Swainson's thrush; we hypothesize that the pure forms will have divergent migratory routes, while the hybrids will have intermediate routes and will suffer higher mortality. There are many migratory divides known in birds, and our study will be the first to directly test the idea that hybrids are selected against because of inferior migratory behaviors.