Complex interactions can create persistent fluctuations in high-diversity ecosystems
Complex interactions can create persistent fluctuations in high-diversity ecosystems
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DOI：
10.1371/journal.pcbi.1007827
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发表时间：
2020-05-01
影响因子：
4.3
通讯作者：
Bunin, Guy
中科院分区：
文献类型：
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作者：
Roy, Felix;Barbier, Matthieu;Bunin, Guy
生态相互作用何时才能使整个生态系统进入持久的非平衡状态，使许多物种种群发生波动而不会灭绝？我们表明，高多样性的空间异质系统可以表现出持续极长时间的混沌动力学。我们开发了一个基于动态平均场理论的理论框架，以量化这些波动状态存在的条件，并预测它们的特性。我们发现了与外部扰动生态系统的持久性的相似之处，例如扰动强度、同步性和相关时间的作用。但对于内生波动而言，这些特性是由物种动态本身产生的，在扰动和响应之间形成反馈循环。一个关键的结果是，波动幅度和物种多样性紧密相关：特别是，在同一系统中，波动使得比平衡状态下的物种共存要多得多。我们的研究结果强调了混合良好的系统和空间扩展的系统之间的关键差异，这对实验及其再现自然动态的能力具有重要意义。它们揭示了生物多样性的维护以及自然系统中观察到的波动的强度和同步性。作者摘要自然种群中的大量丰度波动有充分的记录。然而，目前尚不清楚这些波动在多大程度上源于多物种相互作用，而不是环境扰动或人口统计过程。关于这些问题长期以来一直存在争论，甚至质疑相互作用驱动的波动的可能性，因为它们可能会导致物种灭绝，直到达到平衡。在复杂的高维环境（许多相互作用的物种、许多生态位等）中，情况变得更具挑战性和更丰富，这些环境具有性质上的新现象，并且仍然缺乏理论。在这里，我们表明，高多样性元群落可以在极长的时间内持续处于动态波动状态而不会灭绝，并且其多样性远高于平衡时所达到的多样性。我们描述了这些内生波动的定量条件，以及将它们与外部扰动区分开的关键指纹。我们建立了多物种动力学的理论框架，该框架源自非平衡系统的统计物理学。这些环境提出了独特的挑战，观察到的行为可能是违反直觉的，这使得专门的理论技术成为不可或缺的工具。我们的理论准确地将多物种问题映射到单一代表性物种（集合种群）的问题。这使我们能够与有关受扰动的集合种群的现有理论建立联系，同时考虑到高度多样性的内源反馈的独特属性。
When can ecological interactions drive an entire ecosystem into a persistent non-equilibrium state, where many species populations fluctuate without going to extinction? We show that high-diversity spatially heterogeneous systems can exhibit chaotic dynamics which persist for extremely long times. We develop a theoretical framework, based on dynamical mean-field theory, to quantify the conditions under which these fluctuating states exist, and predict their properties. We uncover parallels with the persistence of externally-perturbed ecosystems, such as the role of perturbation strength, synchrony and correlation time. But uniquely to endogenous fluctuations, these properties arise from the species dynamics themselves, creating feedback loops between perturbation and response. A key result is that fluctuation amplitude and species diversity are tightly linked: in particular, fluctuations enable dramatically more species to coexist than at equilibrium in the very same system. Our findings highlight crucial differences between well-mixed and spatially-extended systems, with implications for experiments and their ability to reproduce natural dynamics. They shed light on the maintenance of biodiversity, and the strength and synchrony of fluctuations observed in natural systems.Author summaryLarge abundance fluctuations are well-documented in natural populations. Yet, it is still not known to what extent these fluctuations stem from multi-species interactions, rather than environmental perturbations or demographic processes. There have been long-standing debates on these issues, questioning even the possibility of interaction-driven fluctuations, as they might induce species extinctions until equilibrium is reached.The situation is all the more challenging and richer in complex high-dimensional settings (many interacting species, many niches, etc.), which feature qualitatively new phenomena, and where theory is still lacking. Here we show that high-diversity metacommunities can persist in dynamically-fluctuating states for extremely long periods of time without extinctions, and with a diversity well above that attained at equilibrium. We describe the quantitative conditions for these endogenous fluctuations, and the key fingerprints which would distinguish them from external perturbations.We establish a theoretical framework for the many-species dynamics, derived from statistical physics of out-of-equilibrium systems. These settings present unique challenges, and observed behaviors may be counter-intuitive, making specialized theoretical techniques an indispensable tool. Our theory exactly maps the many-species problem to that of a single representative species (metapopulation). This allows us to draw connections with existing theory on perturbed metapopulations, while accounting for unique properties of endogenous feedbacks at high diversity.