Environmental thresholds of semiaquatic bugs (Heteroptera, Gerromorpha) as an indicator of environmental change in...

Freshwater ecosystems under the influence of human activities are subject to multiple environmental stressors that lead to biodiversity loss and habitat modification. In recent years, various organisms have been used as bioindicators to detect environmental changes by their ability to perceive changes in community attributes. A good example is the semiaquatic bugs (Hemiptera, infra order Gerromorpha) that act as predators and are sensitive to subtle changes in environmental conditions. Our research aimed to investigate the responses of Gerromorpha communities, genera, and species along an environmental gradient in 45 Amazon streams. The environmental gradient was assessed utilizing the Habitat Integrity Index (HII) across the sampled streams, yielding a collection of 2.212 specimens representing three families, seven genera, and 36 species. The habitat integrity, represented by the HII, showed a positive relationship between species richness and the richness of genera of Gerromorpha, underscoring that both species and genera respond to environmental change in the analyzed habitats. Brachymetra lata (Gerridae), Rhagovelia jubata, and R. elegans (Veliidae) were the most sensitive taxa with a positive relationship to HII. Streams characterized by higher anthropogenic disturbance and reduced riparian vegetation were associated with a biodiversity pattern marked by increased abundance and frequency of generalist species and reduced genus frequency within the Veliidae family. We hope that the results of this study will contribute to future biomonitoring programs in response to habitat and species loss, aiming to assist decision-making to protect and restore riparian vegetation areas.