Origins and maintenance of diversity

生物多样性是从哪里来的，为什么全球各地的生物多样性会有所不同？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了解(I)新物种是如何形成的，(Ii)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(Iii)造成广泛的地理多样性差异的原因。(I)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(Zonotricia Atricapilla)-以及使这一物种有别于其近亲白冠麻雀(Z.leucoprys)的特征。通过在鸟类养殖场的实验，我们将询问雌性更喜欢哪种物种，以及它们用什么特征来做出决定。然后，我们将使用交叉养育实验--其中一个物种是由另一个物种抚养长大的--来检验这样一个假设，即择偶是基于父母在很小的时候就留下的印记。(Ii)一旦新物种形成，它们可能需要很长时间才能真正共存。我们将研究发生在加拿大东部的林莺从物种形成到共存的过程。使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、生态和行为互动，以及这些是如何随着分化以来的时间量而变化的。(Iii)向赤道方向的多样性在纬度上增加的原因是生物学中最悬而未决的问题之一。我们正在研究进化模式如何随纬度变化，特别是为什么我们看到高纬度地区进化速度更快的证据，这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田野工作来检验解释高纬度鸟类更快进化的假说，并进一步询问这与新物种形成速度的纬度变化有何关系。总体而言，拟议的工作将显著提高我们对生物多样性的理解，并将有助于加拿大其他处于该领域前沿的研究。

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.