Dispersal promotes compensatory dynamics and stability in forced metacommunities

Understanding the factors that govern the stability of populations and communities has gained increasing importance as habitat fragmentation and environmental perturbations continue to escalate due to human activities. Dispersal is commonly viewed as essential to the maintenance of diversity in spatially subdivided communities, but few experiments have explored how dispersal interacts with the spatiotemporal components of environmental perturbations to determine community-level stability. We examined these processes using an experimental planktonic system composed of three competing species of zooplankton. We subjected zooplankton metacommunities to varying levels of dispersal and pH perturbations that varied in their degree of spatial synchrony. We show that dispersal can reverse the destabilizing effects of environmental forcing when perturbations are spatially asynchronous. Asynchrony in pH perturbations generated spatially and temporally varying species refugia that promoted source-sink dynamics and allowed prolonged persistence of zooplankton species that were otherwise extirpated in synchronously varying metacommunities. This, in turn, increased local species diversity, promoted compensatory population dynamics and enhanced local community-level stability. Our results indicate that patterns of spatial covariation in environmental variability are critical to predicting the effects of dispersal on the dynamics and persistence of communities.随着人类活动持续加剧生境破碎化与环境扰动，解析调控种群与群落稳定性的核心因子，其重要性日益凸显。扩散通常被视为维持空间分隔群落多样性的必要条件，但目前鲜有实验探究扩散如何与环境扰动的时空属性相互作用，进而决定群落尺度的稳定性。本研究借助由三种竞争性浮游动物构成的实验浮游系统，对上述过程展开了系统性探究。我们对浮游动物集合群落（metacommunity）施加了不同强度的扩散处理，以及空间同步性各异的pH扰动。研究结果表明，当扰动呈现空间异步性时，扩散可逆转环境胁迫的去稳定化效应。pH扰动的异步性会生成时空异质性的物种避难所，进而催生源-汇动态（source-sink dynamics），使得原本在同步扰动的集合群落中会被彻底灭绝的浮游动物物种得以长期存续。这一过程继而提升了局域物种多样性，推动了补偿性种群动态，并增强了局域群落尺度的稳定性。本研究结果显示，环境变异的空间协变模式，是预测扩散对群落动态与物种存续影响的关键依据。