Department of Biology, Indiana University, Bloomington, Indiana, United States of America.
Department of Environmental Sciences, Copernicus Institute of Sustainable Development, Utrecht University, Utrecht, the Netherlands.
PLoS One. 2019 Feb 11;14(2):e0211572. doi: 10.1371/journal.pone.0211572. eCollection 2019.
Both ecological theory and empirical evidence suggest that negative frequency dependent feedbacks structure plant communities, but integration of these findings has been limited. Here we develop a generic model of frequency dependent feedback to analyze coexistence and invasibility in random theoretical and real communities for which frequency dependence through plant-soil feedbacks (PSFs) was determined empirically. We investigated community stability and invasibility by means of mechanistic analysis of invasion conditions and numerical simulations. We found that communities fall along a spectrum of coexistence types ranging from strict pair-wise negative feedback to strict intransitive networks. Intermediate community structures characterized by partial intransitivity may feature "keystone competitors" which disproportionately influence community stability. Real communities were characterized by stronger negative feedback and higher robustness to species loss than randomly assembled communities. Partial intransitivity became increasingly likely in more diverse communities. The results presented here theoretically explain why more diverse communities are characterized by stronger negative frequency dependent feedbacks, a pattern previously encountered in observational studies. Natural communities are more likely to be maintained by strict negative plant-soil feedback than expected by chance, but our results also show that community stability often depends on partial intransitivity. These results suggest that plant-soil feedbacks can facilitate coexistence in multi-species communities, but that these feedbacks may also initiate cascading effects on community diversity following from single-species loss.
生态理论和经验证据表明，负频率依赖反馈结构植物群落，但这些发现的整合受到限制。在这里，我们开发了一个通用的频率依赖反馈模型，以分析随机理论和真实群落中的共存和入侵性，这些群落通过植物-土壤反馈（PSFs）的频率依赖性得到了经验上的确定。我们通过入侵条件的机制分析和数值模拟来研究群落稳定性和可入侵性。我们发现，群落沿着共存类型的光谱分布，从严格的成对负反馈到严格的不可传递网络。以部分不可传递性为特征的中间群落结构可能具有“关键竞争者”，它们不成比例地影响群落稳定性。真实群落的负反馈比随机组装群落更强，对物种损失的鲁棒性更高。更多样化的群落中，部分不可传递性变得越来越有可能。这里提出的结果从理论上解释了为什么更多样化的群落具有更强的负频率依赖反馈，这是以前在观察研究中遇到的模式。自然群落通过严格的负植物-土壤反馈来维持的可能性比随机的可能性更大，但我们的结果也表明，群落稳定性通常取决于部分不可传递性。这些结果表明，植物-土壤反馈可以促进多物种群落的共存，但这些反馈也可能会引发单一物种损失后对群落多样性的级联效应。
