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

理解生物多样性最令人困惑的挑战之一是确定物种丰度在时间和空间上波动的重要性。科学家们已经证明，物种特有的波动对于维持物种多样性是必要的，但众所周知，波动也会导致物种灭绝。此外，大多数物种生活在空间上错落有致的栖息地，容易出现较大的波动。协调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导致不同的结果。*在这个提案中，我的实验室将测试两个鲜为人知的波动来源的流行率和后果，这两个来源在斑驳的栖息地中很常见。第一种是生态漂移，是由人口随机性导致的群落随机变化的过程，以及这种随机性是如何通过生态相互作用来减弱或传播的。有几个人呼吁将漂移作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。这将得到对食物网漂移的平行研究的补充，重点是随机程度如何跨越营养水平。这两项经验研究都将被用来为理论模型提供信息，这些模型将正式确定栖息地斑块大小、物种相互作用、物种间人口随机性差异和个体大小对生态漂移的重要性。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所产生的波动的普遍性和影响。大多数系统对这些反馈知之甚少，但斑块内和景观之间的结构多样性。重要的是，当地的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，但也使这种理解对于保护至关重要。我们将使用一个自然支离破碎的专业植物-草食系统来估计草食动物取食速度、扩散速度和对植物的影响随温度的变化，以及由此产生的植物斑块和草食物种局部丰度的变化。我们将使用这些参数来预测长期温度变化和温度波动如何改变局部相互作用和扩散之间的动态反馈，并使用观察性研究和大规模实验元群落来检验这些预测。总体而言，这些关于物种波动的原因和后果的研究将解决在理解生物多样性如何维持方面的根本差距，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.***