Microbial communities can have dramatically different compositions even among similar environments. This might be due to the existence of multiple alternative stable states, yet there exists little experimental evidence supporting this possibility. Here, we gathered a large collection of absolute population abundances capturing population dynamics in one- to four-strain communities of soil bacteria with a complex life cycle in a feast-or-famine environment. This dataset led to several observations: (i) some pairwise competitions resulted in bistability with a separatrix near a 1:1 initial ratio across a range of population densities; (ii) bistability propagated to multi-stability in multispecies communities; and (iii) replicate microbial communities reached different stable states when starting close to initial conditions separating basins of attraction, indicating finite-sized regions where the dynamics are unpredictable. The generalized Lotka–Volterra equations qualitatively captured most competition outcomes but were unable to quantitatively recapitulate the observed dynamics. This was partly due to complex and diverse growth dynamics in monocultures that ranged from Allee effects to nonmonotonic behaviors. Overall, our results highlight that multi-stability might be generic in multispecies communities and, combined with ecological noise, can lead to unpredictable community assembly, even in simple environments.

中文翻译：

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多稳定的细菌群落对初始条件表现出极大的敏感性

即使在相似的环境中，微生物群落的组成也可能截然不同。这可能是由于存在多种替代稳定状态，但几乎没有实验证据支持这种可能性。在这里，我们收集了大量绝对种群丰度，捕捉了在盛宴或饥荒环境中具有复杂生命周期的一到四株土壤细菌群落中的种群动态。该数据集导致了几个观察结果：（i）一些成对竞争导致双稳态，分离线在一系列人口密度范围内的初始比率接近 1:1；(ii) 双稳态传播到多物种群落中的多稳态；(iii) 复制的微生物群落在接近分离吸引盆地的初始条件开始时达到不同的稳定状态，表明动态不可预测的有限大小区域。广义 Lotka-Volterra 方程定性地捕捉了大多数竞争结果，但无法定量地概括观察到的动态。这部分是由于单一文化中复杂多样的增长动态，从 Allee 效应到非单调行为。总体而言，我们的结果强调，多稳定性可能在多物种群落中具有普遍性，并且与生态噪声相结合，即使在简单的环境中也可能导致不可预测的群落组装。广义 Lotka-Volterra 方程定性地捕捉了大多数竞争结果，但无法定量地概括观察到的动态。这部分是由于单一文化中复杂多样的增长动态，从 Allee 效应到非单调行为。总体而言，我们的结果强调，多稳定性可能在多物种群落中具有普遍性，并且与生态噪声相结合，即使在简单的环境中也可能导致不可预测的群落组装。广义 Lotka-Volterra 方程定性地捕捉了大多数竞争结果，但无法定量地概括观察到的动态。这部分是由于单一文化中复杂多样的增长动态，从 Allee 效应到非单调行为。总体而言，我们的结果强调，多稳定性可能在多物种群落中具有普遍性，并且与生态噪声相结合，即使在简单的环境中也可能导致不可预测的群落组装。