Stream habitats and human disturbances explain the diversity of Nepomorpha (Heteroptera) assemblages in Neotropical Savanna headwater streams

The organisms of the infraorder Nepomorpha (Heteroptera) present complex habitat requirements in headwater streams, usually being related to local substrate conditions. Therefore, in this study, we evaluated how the diversity of Nepomorpha responded to a wide gradient of habitat and ecological conditions. We tested two hypotheses: (1) local substrate composition is the most important factor determining the diversity of Nepomorpha compared to other physical habitat metrics, (2) Nepomorpha assemblage diversity respond more readily to anthropogenic disturbances at local scale. Our results did not corroborate the first hypothesis, and showed that the assemblage diversity was mostly related to water quality and geomorphology, indicating that substrate requirements are not the only important driver. Our second hypothesis was partially corroborated, as all diversity metrics presented significant correlation with human disturbances at both local and catchment spatial scales. These results show that Nepomorpha assemblages have high potential use as ecological indicators, which should be better explored in future biomonitoring studies of anthropogenic changes.