Synchrony in Metapopulations at Multiple Time-Scales: Theory, Experiments and Field Data

该项目旨在了解一个物种（称为元种群）在空间上不同的种群如何以及为什么在植物和动物数量上显示同步波动。种群间的同步性对保护生物学具有重要意义。同步性意味着，有时超种群可能同时稀少，这增加了灭绝的可能性。同步性源于种群间的迁移和影响多个种群的环境变化。这两种机制的相对重要性尚不清楚。现有的同步分析统计方法存在不足。两个种群时间序列之间的同步程度通常用一个数字来衡量，比如相关系数。然而，两个时间序列之间的同步性强度可以随着时间尺度的变化而变化，也就是说，同步性可能具有频率特定的成分。为了加深对元人口同步的认识，本项目将(1)分析大型时空生态数据库的数据，(2)发展新的理论和统计方法，(3)开展新的实验室实验。对气候变化、灭绝风险和驱动同步的机制（迁移和环境变化）的影响将进行评估。将分析环境变量和种群数量的长空间广泛时间序列，以表征同步的特定频率性质。数学模型的分析和数值分析将对特定频率的环境同步性如何影响种群同步性和元种群灭绝的概率提出理论期望。对面粉甲虫实验室种群的实验将在几个方面扩展早期的研究。首先，调查人员对环境和人口同步采取了特定时间尺度的观点。其次，他们考察了平衡种群和混沌种群。先前的理论工作表明，这两种动力学对同步过程的响应不同。第三，他们的实验将涉及两个兄弟物种的昆虫，它们的种群动态受不同的密度依赖机制控制：未成熟阶段的同类相食和变态的延迟。前者导致对扰动的快速反应，并增加人口周期的趋势，而后者导致对扰动和非周期动力学的缓慢反应。两种物种的使用将允许对实验结果的一般性进行评估。这种多学科方法将增强我们对生态同步性及其与社会的相关性的理解。该项目将对全球气候变化对物种灭绝的影响具有重要的实际意义，并将导致更复杂的方法来保护种群分散的受威胁或濒危物种。这项研究将利用现有的生态数据库，并将产生和传播高质量的实验室数据，这些数据可以用来进一步了解环境变化、扩散和种群动态之间的相互作用。所开发的数学和统计工具将扩展检查同步的传统方法，以考虑不同的时间尺度，并将适用于来自其他领域的数据。该项目还将促进本科生和研究生的跨学科教育，包括代表性不足的群体，并将编制和分发教学材料，以便利在本科生和研究生一级使用面粉甲虫系统进行数量生态学训练。

This project aims to understand how and why collections of spatially distinct populations of a species (called metapopulations) display synchronous fluctuations in plant and animal numbers. Synchrony among populations has a serious implication for conservation biology. Synchrony means that metapopulations, on occasion, can be simultaneously rare which enhances the likelihood of extinction. Synchrony results from migration among populations and from environmental variation that affects multiple populations. The relative importance of these two mechanisms remains unknown. The current statistical methods of analyzing synchrony have shortcomings. The degree of synchrony between two population time series is usually measured by a single number, such as a correlation coefficient. However, the strength of synchrony between two time series can vary with the time scale on which it is examined, that is, synchrony may have frequency-specific components. To increase our understanding of metapopulation synchrony, this project will (1) analyze data from large spatio-temporal ecological databases, (2) develop new theory and statistical methods, and (3) conduct new laboratory experiments. The implications for climate change, extinction risks, and the mechanisms that drive synchrony (migration and environmental variation) will be assessed. Long spatially-extensive time series of environmental variables and population numbers will be analyzed to characterize the frequency-specific nature of synchrony. Analytical and numerical analyses of mathematical models will develop theoretical expectations for how frequency-specific environmental synchrony affects population synchrony and probabilities of metapopulation extinction. Experiments with laboratory populations of flour beetles will extend earlier studies in several ways. First, the investigators take a time-scale-specific perspective on both environmental and population synchrony. Second, they examine both equilibrium and chaotic populations. Previous theoretical work has show that these two dynamics respond differently to synchronizing processes. Third, their experiments will involve two sibling species of insects whose population dynamics are controlled by different density-dependent mechanisms: cannibalism of immature life stages and delay of metamorphosis. The former leads to rapid responses to perturbations and increases the tendency for demographic cycles whereas the latter leads to slow responses to perturbations and non-cyclic dynamics. The use of both species will allow an evaluation of the generality of the experimental results. This multidisciplinary approach will enhance our understanding of ecological synchrony and its relevance to society.This project will have important practical implications for the effects of global climate change on species extinction and will lead to more sophisticated methods for conserving threatened or endangered species whose populations have become fragmented. The research will capitalize on existing ecological databases and will generate and disseminate high quality laboratory data that can be used to further our understanding of the interactions among environmental variation, dispersal, and population dynamics. The mathematical and statistical tools developed will extend the traditional methods for examining synchrony to consider different time scales and will be applicable to data from other fields. The project will also contribute to the interdisciplinary education of undergraduates and graduate students, including underrepresented groups, and will create and distribute instructional materials to facilitate the use of the flour beetle system for training in quantitative ecology at the undergraduate and graduate levels.