Ecological and evolutionary dynamics

自然生态系统最显著的特征之一是其物种的巨大多样性。这种多样性在不同的地点和时间会有所不同。不那么明显，但同样引人注目的是进化多样性：表型和基因频率的时空变化。这种变化是如何产生和维护的？这些问题是基础生态学和进化研究的根本问题，也是生物多样性保护的基础。在基本层面上，我们知道答案：任何一种生物的丰度都取决于它的出生、死亡和在不同地点之间移动的速度（在更长的时间尺度上，独特的进化力量，如物种形成，会起作用）。但是计算出细节是极其困难的，因为出生率、死亡率和迁移率在空间和时间上变化很大，并且取决于许多因素。****我的研究解决了出生、死亡和运动的基本过程如何在生物多样性中产生模式，使用模型系统，这些过程的速率可以被测量和操纵。我的提案描述了三组解决不同问题的项目：(1)人口和环境随机性如何与确定性力量相互作用，以驱动人口和社区动态？我建议用由快速生长的原生生物和细菌组成的实验室微观群落来回答这个问题。这个系统允许我直接操纵人口随机性和其他因素的强度，这在大多数其他系统中是不可能的。(2)时间环境变异是否能像空间变异一样有效地维持遗传多样性？我建议通过测试湖泊细菌对水化学时空变化的局部适应性来回答这个问题，使用我开发的一种新方案来在时间和空间上移植细菌。(3)物种间相互作用如何影响局部适应和物种沿环境梯度的分布？我建议研究生物环境（邻近植物）如何影响高山植物如何适应其恶劣的非生物环境，从而影响沿海拔梯度的适应性遗传变异的维持，并决定物种的海拔范围限制。****提出的研究是假设驱动的。它结合了解决经典问题的新方法和对以前没有解决过的问题的直接攻击。这些结果将提高我们对随机性的理解，提供关于环境波动是否维持遗传多样性的第一个实地数据，并解决有关范围限制的生态和进化决定因素的开放性问题。除了有助于基本理解外，拟议的工作将为7名研究生提供培训，并为至少13名本科生提供研究经验

One of the most striking features of natural ecosystems is their great diversity of species. This diversity can vary among sites and over time. Less obvious, but equally striking, is evolutionary diversity: temporal and spatial variation in phenotypes and gene frequencies. How is this variation generated and maintained? These questions are of fundamental interest for basic ecological and evolutionary research, and also underpin the conservation of biodiversity. At a basic level, we know the answer: the abundance of any type of organism just depends on the rates at which it gives birth, dies, and moves between sites (and on longer timescales uniquely-evolutionary forces like speciation come into play). But working out the details is extremely difficult, since rates of birth, death, and movement can vary greatly in space and time and depend on many factors.****My research addresses how the fundamental processes of birth, death, and movement generate patterns in biodiversity using model systems in which the rates of these processes can be measured and manipulated.  My proposal describes three sets of projects addressing different questions: (1) How do demographic and environmental stochasticity interact with deterministic forces to drive population and community dynamics? I propose to answer this question with laboratory microcosm communities comprised of fast-growing protists and bacteria. This system allows me to directly manipulate the strength of demographic stochasticity and other factors, manipulations that are impossible in most other systems. (2) Can temporal environmental variation maintain genetic diversity as effectively as spatial variation? I propose to answer this question by testing for local adaptation of lake bacteria to spatial and temporal variation in water chemistry, using a novel protocol I have developed to transplant bacteria in time as well as space. (3) How do species interactions affect local adaptation and species distributions along environmental gradients? I propose to examine how the biotic environment (neighboring plants) affects how alpine plants adapt to their harsh abiotic environment, thereby affecting the maintenance of adaptive genetic variation along elevational gradients and determining species' elevational range limits. ****The proposed research is hypothesis-driven. It combines new approaches to classic problems with direct attacks on problems that have not previously been addressed. The results will improve our understanding of stochasticity, provide the first field data on whether environmental fluctuations maintain genetic diversity, and resolve open questions about the ecological and evolutionary determinants of range limits. Besides contributing to fundamental understanding, the proposed work will provide training for 7 graduate students and provide research experience for at least 13 undergraduates.**