Copernicus Institute of Sustainable Development, Environmental Sciences, Faculty of Geosciences, Utrecht University, Utrecht, the Netherlands.
Department of Earth and Environmental Sciences, Los Alamos National Laboratory, Los Alamos, NM, USA.
Nat Ecol Evol. 2018 Sep;2(9):1403-1407. doi: 10.1038/s41559-018-0622-3. Epub 2018 Jul 30.
Ecological theory suggests that coexistence of many species within communities requires negative frequency-dependent feedbacks to prevent exclusion of the least fit species. For plant communities, empirical evidence of negative frequency dependence driving species coexistence and diversity patterns is rapidly accumulating, but connecting these findings to theory has been difficult as corresponding theoretical frameworks only consider small numbers of species. Here, we show how frequency-dependent feedback constrains community coexistence, regardless of the number of species and inherent fitness inequalities between them. Any interaction network can be characterized by a single community interaction coefficient, I, which determines whether community-level feedback is positive or negative. Negative feedback is a necessary (but not sufficient) condition for persistence of the entire community. Even in cases where the coexistence equilibrium state cannot recover from perturbations, I < 0 can enable species persistence via cyclic succession. The number of coexisting species is predicted to increase with the average strength of negative feedback. This prediction is supported by patterns of tree species diversity in more than 200,000 deciduous forest plots in the eastern United States, which can be reproduced in simulations that span the observed range of community feedback. By providing a quantitative metric for the strength of negative feedback needed for coexistence, we can now integrate theory and empirical data to test whether observed feedback-diversity correlations are strong enough to infer causality.
生态理论表明，群落中多种物种的共存需要负频率依赖性反馈，以防止适应能力最差的物种被排斥。对于植物群落，负频率依赖性驱动物种共存和多样性模式的经验证据正在迅速积累，但将这些发现与理论联系起来一直很困难，因为相应的理论框架只考虑少数几种物种。在这里，我们展示了无论物种数量和它们之间固有的适应能力不平等如何，频率依赖性反馈如何限制群落共存。任何相互作用网络都可以用单个社区相互作用系数 I 来描述，它决定了社区层面的反馈是正的还是负的。负反馈是整个社区持续存在的必要（但不是充分）条件。即使在共存平衡状态不能从扰动中恢复的情况下，I < 0 也可以通过循环演替使物种持续存在。共存的物种数量预计会随着负反馈的平均强度增加而增加。这一预测得到了美国东部超过 20 万个落叶林样地的树种多样性模式的支持，这些模式可以在模拟中重现，模拟范围涵盖了观察到的社区反馈范围。通过为共存所需的负反馈强度提供一个定量指标，我们现在可以将理论和经验数据结合起来，以检验观察到的反馈-多样性相关性是否足够强，可以推断出因果关系。
