Coexistence and food web theory are two cornerstones of the long-standing effort to understand how species coexist. Although competition and predation are known to act simultaneously in communities, theory and empirical study of these processes continue to be developed largely independently. Here, we integrate modern coexistence theory and food web theory to simultaneously quantify the relative importance of predation and environmental fluctuations for species coexistence. We first examine coexistence in a theoretical, multitrophic model, adding complexity to the food web using machine learning approaches. We then apply our framework to a stochastic model of the rocky intertidal food web, partitioning empirical coexistence dynamics. We find the main effects of both environmental fluctuations and variation in predator abundances contribute substantially to species coexistence. Unexpectedly, their interaction tends to destabilise coexistence, leading to new insights about the role of bottom-up vs. top-down forces in both theory and the rocky intertidal ecosystem.

中文翻译：

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量化捕食和环境变化对物种共存的相对重要性。

共存和食物网理论是理解物种共存的长期努力的两个基石。尽管竞争和掠夺在社区中是同时发生的，但是这些过程的理论和经验研究仍在很大程度上独立地发展。在这里，我们结合了现代共存理论和食物网理论，以同时量化捕食和环境波动对物种共存的相对重要性。我们首先在理论上，多营养的模型中研究共存，然后使用机器学习方法为食物网增加复杂性。然后，我们将框架应用于潮间带岩石食物网的随机模型，划分经验共存动力学。我们发现环境波动和捕食者数量变化的主要影响在很大程度上促进了物种共存。出乎意料的是，它们之间的相互作用往往会破坏共存的稳定性，从而导致人们对自下而上与自上而下的力量在理论和潮间带生态系统中的作用有了新的认识。