Data from: Allelopathy prevents competitive exclusion and promotes phytoplankton biodiversity

It has been hypothesized that allelopathy can prevent competitive exclusion and promote phytoplankton diversity in aquatic ecosystems, where numerous species coexist on a limited number of resources. However, experimental proof-of-principle is not available to support this hypothesis. Here we present the first experimental evidence to support this hypothesis by demonstrating that allelopathy promotes the coexistence of two phytoplankton species, Ankistrodesmus falcatus and Oscillatoria sp., that compete for a single limiting nutrient. By performing long-term competition experiments in nitrate-limited continuous cultures, and by describing the population dynamics using a mechanistic model, we demonstrate that when allelopathy comes into play, one of the following outcomes is possible depending on the relative initial abundances of the species: dominance of the stronger competitor for nitrate (the non-allelopathic species), oscillatory coexistence, or dominance of the weaker competitor (the allelopathic species). Our model analysis revealed that sustained oscillatory coexistence of the two species would be a common outcome of this experiment. Our study confirms for the first time, based on laboratory experiments combined with mechanistic models, that allelopathy can alter the predicted outcome of inter-specific competition in a nutrient-limited environment and increase the potential for the coexistence of more species than resources, thereby contributing to the identification of endogenous mechanisms that explain the extreme diversity of phytoplankton communities.已有研究提出假说：化感作用（allelopathy）可在水生生态系统中阻止竞争排斥，并促进浮游植物（phytoplankton）多样性——在这类系统中，众多物种依托有限的资源实现共存。然而，目前尚无支撑该假说的原理性实验证据。本研究首次提供了支持该假说的实验证据：我们证实化感作用可促进两种浮游植物——镰形纤维藻（Ankistrodesmus falcatus）与颤藻属未定种（Oscillatoria sp.）——的共存，二者竞争单一限制性营养盐。我们通过在硝酸盐限制的连续培养体系中开展长期竞争实验，并借助机理模型描述种群动态，证实当化感作用发挥作用时，依据物种的初始相对丰度，可出现以下三种结果之一：对硝酸盐竞争能力更强的物种（非化感物种）占据优势、振荡共存，或是竞争能力较弱的物种（化感物种）占据优势。模型分析显示，两种物种的持续振荡共存将是本实验的常见结果。本研究首次结合实验室实验与机理模型证实：在营养盐限制的环境中，化感作用可改变种间竞争的理论预测结果，并提升物种数多于资源数时的共存可能性，从而助力阐明解释浮游植物群落极端多样性的内生机制。