The biogeographic drivers and genomic architecture of speciation in Amazonian birds

与高纬度地区相比，热带地区拥有异乎寻常的物种数量。我的研究调查了导致热带地区高度生物多样性过剩的因素。一个关键的理论将热带地区的高生物多样性与新物种形成的快速速度联系起来，要么是因为热带地区拥有更多促进物种多样化的地理障碍，要么是因为不同的种群进化得更快，成为不同的物种。我的研究计划的两个主要方向是对许多物种进行比较分析，以解决1)物种形成的地理环境，以及2)种群遗传进化成为新物种的速度。这些比较分析是在地球上生物多样性最丰富的热点地区——亚马逊雨林——和高纬度地区生物多样性低的地区，如加拿大进行的。对于这两个流，我将使用尖端的下一代测序数据集，包括数千个遗传标记，允许在不同假设之间区分无与伦比的敏感性。第一批项目将调查冰期降温期间森林破碎化、宽河流屏障和生态梯度对亚马逊地区新物种形成的贡献。每一种地理情景都做出了不同的预测，这些预测可以通过将人口历史的人口统计学模型与大型遗传数据集相匹配来检验。第二组项目将测试热带和温带地区新形成物种基因分化的进化速度。在地理屏障隔离之后，种群开始积累遗传差异，最终导致生殖隔离——无法相互生育成功的后代。生殖隔离标志着新物种形成过程的完成，并且在新物种出现后对维持其多样性至关重要。我的实验室将通过分析仍在杂交并处于成为不同物种的中间阶段的成对种群中的数千个遗传标记，研究对生殖隔离至关重要的遗传差异产生的速度。我们将量化未能跨越种群边界的遗传标记的比例（这些标记表明可能存在导致生殖隔离的基因），并使用这些标记以及杂交种群分化的日期来确定热带或温带地区的生殖隔离率是否发展得更快。

The tropics possess exceptional numbers of species when compared to high latitudes. My research investigates the factors that drive the excess of high biodiversity in tropical regions. A key theory links high tropical biodiversity to a fast rate at which new species form, either because the tropics possess more geographic barriers that promote species diversification, or because diverging populations evolve more rapidly to become distinct species. The two major streams of my research program use comparative analyses across many species to address 1) the geographic setting of species formation, and 2) the rates at which populations evolved genetically to become new species. These comparative analyses are performed in the most biodiverse hotspot on our planet – the Amazon rainforest – versus low biodiversity areas at high latitude regions, like Canada. For both streams, I will use cutting-edge next generation sequencing datasets comprising thousands of genetic markers that allow for unparalleled sensitivity in discriminating between alternative hypotheses. The first set of projects will investigate the contribution of forest fragmentation during periods of ice age cooling, wide river barriers, and ecological gradients to the formation of new species in the Amazon. Each of these geographic scenarios make distinct predictions that can be tested by fitting demographic models of population history to large genetic datasets. The second set of projects will test the evolutionary speed at which newly formed species diverge genetically in tropical versus temperate regions. Following isolation by geographic barriers, populations begin to accumulate genetic differences, which eventually result in reproductive isolation – the inability to produce successful offspring with each other. Reproductive isolation marks the completion of the process by which new species form and is vital to the maintenance of diversity once it arises. My lab will study the pace at which genetic differences important to reproductive isolation arise by analyzing thousands of genetic markers in pairs of populations which still hybridize and are in the intermediate stages of becoming distinct species. We will quantify the proportion of genetic markers that fail to cross population boundaries (such markers indicate the likely presence of a gene causing reproductive isolation) and use these, along with dates at which hybridizing populations diverged, to determine if rates of reproductive isolation evolve faster in tropical or temperate regions.