Black Fly (Diptera: Simuliidae) Assemblages of High Andean Rivers Respond to Environmental and Pollution Gradients.

Simuliid larvae are common inhabitants of mountain rivers throughout the world, where they can serve as ecological indicators. Black flies were sampled during three seasons in four rivers in the upper basin of the Bogotá River in the Colombian Andes, and physical, chemical, and hydrological data were recorded. Multivariate methods were used to determine the relationships between the presence and abundance of simuliid species and environmental characteristics. Fourteen species were found: eight in the genus Gigantodax (Enderlein, Diptera, Simuliidae) and six in the genus Simulium (Latreille, Diptera, Simuliidae). Dissolved oxygen, dissolved solids, redox potential, chemical oxygen demand, and nutrients contributed to an explanation of species distributions. Species in clean waters and in more polluted waters had narrow niches; those in low to moderately polluted waters had broader niches. Species in the lower reaches of the watercourses had greater turnover, perhaps because the most sensitive species had disappeared and been replaced by more tolerant species. Thus, simuliids can be used as predictors of environmental characteristics of Andean rivers and can be useful in the evaluation and management of these watersheds.