Data from: Experimental demonstration of an Allee effect in microbial populations

Microbial populations can be dispersal limited. However, microorganisms that successfully disperse into physiologically ideal environments are not guaranteed to establish. This observation contradicts the Bass-Becking tenet: ‘Everything is everywhere, but the environment selects’. Allee effects (positive density dependence), which manifest in the relationship between initial population density and probability of establishment, could explain this observation. Here, we experimentally demonstrate that small populations of Vibrio fischeri are subject to demographic Allee effects. This positive density dependence becomes stronger in the presence of the bacterivore Cafeteria roenbergensis creating a predator-induced Allee effect. The estimated critical threshold or minimum density required to escape positive density dependence is around 5, 20, or 75 cells mL−1 under conditions of high carbon resources, low carbon resources, or low carbon resources with predation, respectively. This work builds on the foundations of modern microbial ecology, demonstrating mechanisms controlling macroorganisms apply to microorganisms, and provides a useful method to detect Allee effects in data.

微生物种群往往受到扩散限制。然而，即便微生物成功扩散至生理条件适宜的生境中，也未必能够成功定植。这一观测结果与巴斯-贝金法则（Bass-Becking tenet）相悖，该法则表述为"万物无处不在，唯有环境筛选"。阿利效应（Allee effects，即正密度依赖）表现为种群初始密度与定植概率之间的关联，这一效应或可解释上述观测结果。本研究通过实验证实，费氏弧菌（Vibrio fischeri）的小型种群会受到种群统计型阿利效应的影响。当存在食细菌生物罗伦食细菌虫（Cafeteria roenbergensis）时，这种正密度依赖效应会进一步增强，从而产生捕食者介导的阿利效应。经估算，在高碳源、低碳源以及存在捕食的低碳源三种实验条件下，摆脱正密度依赖所需的临界阈值（即最小种群密度）分别约为每毫升5、20或75个菌体。本研究立足于现代微生物生态学的研究基础，证实了调控大型生物的生态学机制同样适用于微生物，并为从实验数据中检测阿利效应提供了一种实用方法。