O'Connor Reilly F, McMeans Bailey C, Rooney Neil, Guzzo Matthew M, Young Joelle D, McCann Kevin S
Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada.
School of Environmental Sciences, University of Guelph, Guelph, Ontario, Canada.
Ecology. 2023 Feb;104(2):e3889. doi: 10.1002/ecy.3889. Epub 2022 Dec 29.
Portfolio effects (PEs) in ecology refer to the suite of phenomenon where the temporal variation of aggregate ecosystem properties (i.e., abundance) is lower than that of their ecosystem components. An example of this is where differential responses of species to environmental variation generate stability at higher levels of ecological organization (e.g., local community, metapopulation, metacommunity). Most of the research examining such PEs has focused on spatial or interannual variation of ecosystems; however, as global change continues to alter seasonality and ecosystem functioning, understanding the underlying food web structures that help maintain stability at multiple spatial and temporal scales is critical to managing ecological systems. Recent advances investigating diversity-stability relationships has led to the development of frameworks that incorporate a metacommunity perspective which allows for the partitioning of PEs across organizational scales (i.e., local community, metapopulation, cross-community, metacommunity) from local population dynamics (total). This partitioning yields insights into the mechanisms that generate observed PEs in nature. Here, we employed one of these recently developed frameworks on a temporally (1986-1999, 2008-2019) and spatially (five sampling stations, local communities) extensive data set of zooplankton abundance (e.g., density) within a large temperate lake to investigate how temporal (seasonal) and spatial (among site) PEs influence stability within the zooplankton metacommunity. We found that seasonal asynchrony of different zooplankton species within local communities and across communities generated the vast majority of stabilization, while spatial (i.e., metapopulation) dynamics were more synchronous and contributed little to overall system stability. Furthermore, significantly positive diversity-asynchrony relationships at the total, local- and cross-community scales were found as asynchrony was positively correlated with local Shannon diversity. Last, a comparison of PEs over the time periods, during which significant local and global changes (i.e., climate warming, invasive species) have occurred suggests that PEs may be eroding, as increasingly synchronous dynamics and declining diversity in recent years have led to a rise in metacommunity variability. We end by arguing for the critical importance of understanding seasonally driven stabilizing mechanisms as local and global changes threaten to fundamentally alter seasonal signals with potentially strong implications for the structures that lend stability to ecosystems.
生态学中的组合效应（PEs）指的是一系列现象，即生态系统总体属性（如丰度）的时间变化低于其生态系统组成部分的时间变化。一个例子是，物种对环境变化的不同响应在更高层次的生态组织（如当地群落、集合种群、集合群落）中产生稳定性。大多数研究此类组合效应的研究都集中在生态系统的空间或年际变化上；然而，随着全球变化继续改变季节性和生态系统功能，了解有助于在多个空间和时间尺度上维持稳定性的潜在食物网结构对于管理生态系统至关重要。最近在研究多样性 - 稳定性关系方面的进展导致了一些框架的发展，这些框架纳入了集合群落视角，允许从局部种群动态（总体）在不同组织尺度（即当地群落、集合种群、跨群落、集合群落）上对组合效应进行划分。这种划分有助于深入了解自然界中产生观察到的组合效应的机制。在这里，我们在一个大型温带湖泊中，利用一个最近开发的框架，对浮游动物丰度（如密度）的时间（1986 - 1999年，2008 - 2019年）和空间（五个采样站，当地群落）广泛数据集进行研究，以探讨时间（季节性）和空间（站点间）组合效应如何影响浮游动物集合群落内的稳定性。我们发现，当地群落内和跨群落的不同浮游动物物种的季节性异步性产生了绝大部分的稳定性，而空间（即集合种群）动态则更为同步，对整个系统稳定性的贡献很小。此外，在总体、局部和跨群落尺度上发现了显著的正多样性 - 异步性关系，因为异步性与局部香农多样性呈正相关。最后，对在发生了重大局部和全球变化（即气候变暖、入侵物种）的时间段内的组合效应进行比较表明，组合效应可能正在受到侵蚀，因为近年来日益同步的动态和下降的多样性导致了集合群落变异性的增加。我们最后强调，理解季节性驱动的稳定机制至关重要，因为局部和全球变化可能会从根本上改变季节性信号，对赋予生态系统稳定性的结构产生潜在的强烈影响。
