In floodplain lakes, precipitation events shape the environmental heterogeneity and the occurrence of species and functional traits. However, the importance of each biotic and abiotic factor on structuring communities might depend on the local environmental conditions and the identity of such communities. We investigated through Permutational analyses of variance and functional β-diversity components, the effects of neutral and extreme events of precipitation on environmental heterogeneity and distribution of zooplankton functional traits in floodplain lakes. We also examined through distance-based redundancy analysis and fourth-corner analysis, how different variables (physical–chemical, food availability, predation, and temporal dynamics) structure the distribution of zooplankton functional traits and which traits were related to these variables. We used data from six lakes of the Upper Paraná River floodplain over 19 years. Environmental heterogeneity and β-diversity were higher during El Niño and lower during La Niña (extreme rainy and extremely dry season, respectively). Physical–chemical were the variables that most explained zooplankton β-diversity during all seasons and predation during both extreme seasons (La Niña and El Niño). We observed a set of multiple biotic and abiotic factors causing complex effects on zooplankton functional diversity. The homogenization of traits—observed during extreme dry seasons—can lead to losses in ecosystem functions and services if these events continue to be more frequent and intense. We reaffirm the importance of natural flood caused by the rainy seasons to maintain high biotic and abiotic heterogeneity and ecosystem processes.

在洪泛区湖泊中，降水事件决定了环境的异质性以及物种和功能性状的发生。但是，每种生物和非生物因素对构建社区的重要性可能取决于当地的环境条件和此类社区的身份。我们通过方差和功能性β-多样性成分的置换分析，降水中性和极端事件对洪泛区湖泊环境异质性和浮游动物功能性状分布的影响进行了调查。我们还通过基于距离的冗余分析和第四角分析来研究浮游动物功能性状的分布如何构成不同的变量（物理化学，食物可获得性，捕食和时间动态），以及哪些性状与这些变量相关。我们使用了过去19年中上巴拉那河上游平原的六个湖泊的数据。在厄尔尼诺期间，环境异质性和β多样性较高，在拉尼娜期间（分别为极端雨季和极端干旱季节），环境异质性和β多样性较低。物理化学变量是最能解释所有季节浮游动物β多样性以及两个极端季节（拉尼娜和厄尔尼诺）捕食的变量。我们观察到一组多种生物和非生物因素，对浮游动物的功能多样性造成复杂的影响。如果在极端干旱季节观察到的性状均质化，如果这些事件继续更加频繁和激烈，则会导致生态系统功能和服务的丧失。我们重申由雨季引起的自然洪水对于维持高度生物和非生物异质性以及生态系统过程的重要性。