The biogeographic drivers and genomic architecture of speciation in Amazonian birds

点击翻译按钮获取中文摘要

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.