Multispecies interactions: causes and effects of species fluctuations in space and time

了解生物多样性最令人费解的挑战之一是确定物种丰度随时间和空间波动的重要性。科学家们已经证明，物种特有的波动对于维持多样性是必要的，但众所周知，波动会导致物种灭绝。此外，大多数物种发生在空间斑驳的栖息地，容易发生大的波动。调和波动的相反后果需要确定驱动波动的过程，确定这些过程何时以及如何主导生态动态，并理解为什么不同的过程会导致不同的结果。*******在这个提议中，我的实验室将测试在斑块状栖息地中常见的两种不太为人所知的波动来源的流行程度和后果。第一个，生态漂移，是指群体随机变化的过程，这是由人口的随机性引起的，以及这种随机性是如何通过生态相互作用被抑制或传播的。已经有一些人呼吁将漂变形式化为生态学中的一个基本过程。我们的研究测试了漂移在竞争性社区中的重要性，并确定了漂移压倒确定性过程的条件。这将通过对食物网漂移的平行研究来补充，重点是如何在营养水平上衡量随机性。这两项实证研究都将用于理论模型，这些理论模型将形式化生境斑块大小、物种相互作用、种群间人口统计学随机性差异和体型对生态漂变的重要性。*******拟议研究的第二部分将测试由局部相互作用和扩散之间的动态反馈引起的波动的普遍性和影响。大多数系统对这些反馈知之甚少，但在斑块内和景观间结构多样性。重要的是，局部相互作用和扩散依赖于温度，这为了解它们的动态反馈提供了一个独特的机会，同时也使这种理解对保护至关重要。我们将使用一个自然破碎的植物-食草动物系统来估计食草动物取食率、扩散率和对植物的影响的温度依赖性，以及由此导致的植物斑块和食草动物物种的本地丰度的变化。我们将使用这些参数来预测慢性温度变化和波动温度如何改变局部相互作用和扩散之间的动态反馈，并使用观测研究和大规模实验元群落来测试这些预测。*******总的来说，这些关于物种波动的原因和后果的研究将解决理解生物多样性如何维持的根本空白，并为全球变化时代的保护提供新的见解

One of the most perplexing challenges to understanding biodiversity lies in determining the importance of fluctuations in species abundances through time and space. Scientists have shown that species-specific fluctuations are necessary to maintain diversity, yet fluctuations are known to contribute to species extinctions. Moreover, most species occur in spatially patchy habitats, which are prone to large fluctuations. Reconciling the opposing consequences of fluctuations requires identifying processes that drive fluctuations, determining when and how these processes dominate ecological dynamics, and understanding why different processes lead to divergent outcomes.*******In this proposal, my lab will test the prevalence and consequences two poorly-understood sources of fluctuations that are common in patchy habitats. The first, ecological drift, is the process of random change in communities that results from demographic stochasticity, and how this stochasticity is dampened or propagated through ecological interactions. There have been several calls for formalizing drift as a fundamental process in ecology. Our research test the importance of drift in competitive communities, and identify the conditions in which drift overwhelms deterministic processes. This will be complemented by parallel research on drift in food webs, with a focus on how stochasticity scales across trophic levels. Both empirical studies will be used to inform theoretical models that will formalize the importance of habitat patch size, species interactions, among-species differences in demographic stochasticity, and body size on ecological drift.*******The second part of the proposed research will test the prevalence and effects of fluctuations that result from dynamic feedbacks between local interactions and dispersal. These feedbacks are poorly understood for most systems, yet structure diversity within patches and across landscapes. Importantly, local interactions and dispersal are dependent on temperature, providing a unique opportunity to understand their dynamic feedbacks but also making this understanding imperative for conservation. We will use a specialist plant-herbivore system that is naturally fragmented to estimate the temperature-dependence of herbivore feeding rates, dispersal rates and impacts on plants, and resulting changes in plant patchiness and local abundances of herbivore species. We will use these parameters to predict how chronic temperature change and fluctuating temperatures alter dynamic feedbacks between local interactions and dispersal, and test these predictions using observational studies and large-scale experimental metacommunities.*******Overall, these studies of causes and consequences of species fluctuations will address fundamental gaps in understanding how biodiversity is maintained, and provide new insights for conservation in an era of global change.***