Mechanisms of population differentiation and speciation in birds

物种形成通常被定义为种群间生殖隔离的进化。了解物种形成的机制对于理解进化和成功的保护都很重要。然而，这些机制，特别是启动物种形成的障碍，是多方面的，许多问题仍未得到解答。例如，在高度流动的生物中，亲缘关系（在出生地繁殖的倾向）能否单独促进物种形成？非繁殖季节的隔离是否会阻止迁徙动物种群之间的基因流动？同域种群（在时间和空间上共存的同种生物）能形成新物种吗？我的研究小组在海鸟身上解决了类似的问题。具体来说，我们对最近分化或分化的分类群进行了详细的分析，以捕捉正在发生的物种形成，并应用最先进的方法来测试旨在区分不同物种形成模型的明确的先验假设。海鸟为进化遗传学提供了有用的模型，因为它们的生态学通常被很好地理解，而且它们很容易大量取样。我们的工作最初涉及温带和北极物种，然后扩展到热带和亚热带海鸟。在之前的资助周期中，我们发现了同域物种形成的有力证据，并且还表明，与一般理论相反，海鸟的种群分化和物种形成可以在没有地理障碍的情况下发生。在目前的申请中，我建议用海鸟来测试三个一般性问题：(1)按时间隔离（繁殖季节的分离）对促进种群分化和物种形成的重要性；(2)觅食隔离促进种群分化的潜力；(3)在缺乏基因流动地理屏障的种群中，强选择是否会导致遗传分化和物种形成。该项目将为8名研究生和10-15名本科生提供培训，并将有助于我们对进化和生物多样性保护的理解。

Speciation is commonly defined as the evolution of reproductive isolation between populations. Understanding mechanisms of speciation is important both for understanding evolution and for successful conservation. However these mechansims, especially the barriers that initiate speciation, are multi-faceted, and many questions remain unanswered. For example, can philopatry (the tendency to breed at the natal site) alone promote speciation in highly mobile organisms? Does segregation during the nonbreeding season prevent gene flow between populations of migratory animals? Can sympatric populations (conspecific organisms that coexist in time and space) form new species? My research team addresses questions such as these in seabirds. Specifically, we conduct detailed analyses of recently diverged or diverging taxa to catch speciation in action, and apply state-of-the-art methods to test explicit, a priori hypotheses designed to discriminate between alternative models of speciation. Seabirds provide useful models for evolutionary genetics because their ecology is generally well understood, and they are easy to sample in large numbers. Our work initially involved temperate and arctic species, and then expanded to include tropical and subtropical seabirds. In the previous funding cycle, we found strong evidence for sympatric speciation, and also showed that, contrary to general theory, population differentiation and speciation in seabirds can occur in the absence of geographic barriers to gene flow. In the present application, I am proposing to use seabirds to test three general questions: (1) the importance of isolation-by-time (separation of breeding seasons) in promoting population differentiation and speciation; (2) the potential for foraging segregation to promote population differentation; and (3) whether strong selection can lead to genetic differentiation and speciation in populations that lack a geographic barrier to gene flow. This program will provide training for 8 graduate and 10-15 undergraduate students, and will aid both our understanding of evolution and the conservation of biodiversity.