Potential for Trichoptera communities as biological indicators of morphological degradation in riverine systems

Many rivers in southern Africa are increasingly threatened by accelerating geomorphological degradation due to unsustainable agricultural practices and deforestation. Thus, there is a critical need for biological indicators of morphological degradation in running waters. This study analysed the composition and abundance of Trichoptera taxa from 32 sites from rivers in eastern and northwestern Zimbabwe in relation to geomorphological and land use parameters. Redundancy analysis (RDA) and Spearman's rank correlation analysis revealed that species in the genera Anisocentropus, Dyschimus, Lepidostoma, Leptocerina, Athripsodes, Parasetodes, Aethaloptera, Hydropsyche and Polymorphanisus were restricted to undisturbed forested sites, suggesting that these Trichoptera taxa may be used as indicators of structural degradation in watercourses. A species in the genus Hydroptila was the only Trichoptera taxon that showed a statistically significant numerical abundance at disturbed agricultural sites.