The aim of the present study was to identify which variables structure the assemblage of aquatic insects in the subterranean environment, because knowledge about how subterranean communities are structured in rivers with hypogean sections is still emerging. In addition to identifying whether the hypogean assemblage is structured in the same way as the epigean assemblage, we sought to identify whether the environmental restrictions caused by the subterranean habitat resulted in reduced species richness and abundance compared with the epigean habitat. We sampled a 345-m stretch of a stream in Brazil and collected aquatic insects from both the epigean and hypogean environments. In the stream stretch investigated, there was a positive relationship between richness and the percentage of immersion, fine substrate and organic matter, and a negative relationship between richness and conductivity. We also verified differences between the epigean and hypogean environments regarding composition. The variables that best explained the overall assemblage structure included the epigean–hypogean environment and the percentage of coarse and fine substrate. Given the differences between these environments, we emphasise the need for management actions in karst regions that consider the discontinuity of these regions’ river communities to conserve all components of diversity.

本研究的目的是确定在地下环境中哪些变量构成了水生昆虫的聚集体，因为关于在具有次要断面的河流中如何构造地下群落的知识仍在不断涌现。除了确定hypogean组合的结构是否与Epigean组合相同外，我们还试图确定与epigean栖息地相比，地下栖息地引起的环境限制是否导致物种丰富度和丰度降低。我们在巴西的一条345米长的小溪中取样，并从Epigean和hypogean环境中收集了水生昆虫。在调查的河段中，丰富度与浸入，精细基质和有机物的百分比之间呈正相关，浓度与电导率之间呈负相关。我们还验证了Epigean和Hygegean环境之间在成分方面的差异。最能说明整体组装结构的变量包括Epigean-Hypogean环境以及粗糙和精细基底的百分比。考虑到这些环境之间的差异，我们强调在岩溶地区采取管理措施的必要性，考虑到这些地区河流群落的不连续性，以保护多样性的所有组成部分。