Origins and maintenance of diversity

生物多样性从何而来，为什么在全球范围内有所不同？在我们能够准确预测人类活动对世界的未来影响之前，这些都是需要回答的重要问题。我的研究计划的长期目标是更好地理解(1)新物种是如何形成的，(2)这些新物种何时以及如何扩大它们的分布以相互共存，以及(3)多样性的广泛地理差异的原因。(1)为了研究新物种是如何形成的，我们将研究一种最新进化的鸟类——金冠麻雀（Zonotrichia atricapilla）——以及使这个物种与它最近的亲戚白冠麻雀（Z. leucophrys）区别开来的特征。通过在鸟类饲养场进行实验，我们将询问雌性它们更喜欢哪种物种，以及它们用什么特征来做出决定。然后，我们将使用交叉抚养实验——一个物种由另一个物种抚养——来验证这样一个假设，即配偶的选择是基于幼年时对父母的印记。(2)新物种一旦形成，它们可能需要很长时间才能真正彼此共存。我们将研究发生在加拿大东部的林莺（Parulidae: Dendroica）从物种形成到共同共存的过程。利用遗传数据来估计物种分离的时间，我们将研究它们的空间分布、生态和行为相互作用，以及它们如何随着时间的推移而变化。生物多样性沿纬度向赤道方向增加的原因是生物学中尚未解决的最大问题之一。我们正在研究进化模式是如何随着纬度的变化而变化的，特别是研究为什么我们在高纬度地区看到的进化速度更快的证据，与我们可能预期的相反。我们将使用遗传学、生物地理学、博物馆标本和老式的野外工作来检验解释高纬度鸟类更快进化的假说，并进一步探讨这与新物种形成率的纬度变化之间的关系。总的来说，拟议的工作将大大提高我们对生物多样性的理解，并将有助于加拿大在该领域的其他前沿研究。

Where does biodiversity come from, and why does it vary across the globe? These are important questions to answer before we can accurately predict the future impacts of human activities on the world. The long-term goal of my research program is to better understand (I) how new species form, (II) when and how these new species expand their distributions to coexist with one another, and (III) the causes of broad geographic variation in diversity. (I) To study how new species form, we will examine one of the newest species of bird to evolve - the Golden-crowned Sparrow (Zonotrichia atricapilla) - and the traits that keep this species distinct from its closest relative, the White-crowned Sparrow (Z. leucophrys). Using experiments in aviaries, we will ask females which species they prefer, and what traits they use to make their decision. We will then use cross-fostering experiments - where one species is raised by the other - to test the hypothesis that choice of mates is based on imprinting on their parents at an early age. (II) Once new species form, they may take a long time before they actually come to coexist with one another. We will examine the progression from species formation to coexistence together in warblers (Parulidae: Dendroica) occurring in eastern Canada. Using genetic data to estimate how long ago species separated, we will examine their spatial distributions, ecology and behavioural interactions and how these change with the amount of time since divergence. (III) The cause of the latitudinal increase in diversity towards the equator is one of the greatest unsolved questions in biology. We are studying how patterns of evolution vary with latitude, specifically examining why we see evidence for faster rates of evolution at higher latitudes, contrary to what we might expect. We will use genetic, biogeographic, museum specimens, and old fashioned field work to test among hypotheses to explain faster evolution in high latitude birds, and further ask how this relates to latitudinal variation in rates of formation of new species. Overall, the proposed work will significantly improve our understanding of biodiversity, and will contribute to other Canadian research at the forefront of this field.