In freshwater ecosystems, flood pulses, the degree of connectivity between environments, and the vegetation mosaic are among the main variables affecting environmental structure at the landscape scale. At a finer scale, local limnological conditions seem to be more important for structuring river fish assemblages. However, rather than exerting isolated effects, these limnological characteristics can have combined impacts on the environment. We evaluated the main drivers of the spatial structuring of fish trophic guilds in the littoral zone of lakes in the Upper Paraná River floodplain (UPRF) and determined the relative importance of limnological conditions, spatial distance, and riparian vegetation. We sampled fish and limnological variables in June, September, and December of 2011, and classified the fish species into trophic guilds. We used variation partitioning analysis to assess the influence of the three sets of predictors and distance-based redundancy analysis to visualize the position of samples, as described by the composition of trophic guilds in multivariate space. The distribution of trophic guilds was mainly influenced by limnological variables, i.e., conductivity, chlorophyll a, and pH, in periods of low water. Spatial and riparian vegetation predictors, despite being low, also influenced the distribution because limnological variables and riparian vegetation of the UPRF have a well-defined spatial structure due to differences between rivers. The lakes with Class III riparian vegetation (dominated by tree species) supported most of the trophic guilds, including insectivores. This indicates that allochthonous materials, even when they occur in smaller proportions, contribute to the structuring of fish communities in periods of low water.

在淡水生态系统中，洪水脉冲、环境之间的连通性程度和植被镶嵌是影响景观尺度环境结构的主要变量。在更精细的尺度上，当地的湖泊条件似乎对于构建河鱼群落更为重要。然而，这些湖沼学特征不会产生孤立的影响，而是会对环境产生综合影响。我们评估了巴拉那河上游漫滩 (UPRF) 湖泊沿岸带鱼类营养行会空间结构的主要驱动因素，并确定了湖泊条件、空间距离和河岸植被的相对重要性。我们在 2011 年 6 月、9 月和 12 月对鱼类和湖泊学变量进行了采样，并将鱼类分类为营养行会。我们使用变异分区分析来评估三组预测变量的影响，并使用基于距离的冗余分析来可视化样本的位置，如多元空间中营养行会的组成所描述的那样。营养类群的分布主要受湖泊学变量的影响，即电导率、叶绿素a和 pH 值，在低水期。空间和河岸植被预测因子虽然很低，但也影响了分布，因为 UPRF 的湖泊学变量和河岸植被由于河流之间的差异而具有明确的空间结构。具有 III 类河岸植被（以树种为主）的湖泊支持了大部分营养行会，包括食虫动物。这表明外来物质，即使它们以较小的比例出现，也有助于在低水位时期构建鱼类群落。