Hierarchical dynamics influence the distribution of immature black flies (Diptera: Simuliidae)

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lower reaches of the watercourses had greater turnover, perhaps because the most sensitive species had disappeared and been replaced by more tolerant species.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.

Periphytic diatom colonization and litter decomposition in an intermittent stream of South India

We examined the dynamic of periphytic diatom colonization and litter decompositional pattern in an intermittent stream of South India. Litter bags containing 5 g of fresh fallen leaves (belongs to five different species of angiosperms) were fixed in the five stream pools and they were collected after 7, 14, 21, and 28 days of incubation. This experiment showed the diversity, richness, and abundance of diatoms developed on leaf litter. In total, 131 µl^-1 cells of diatoms under four species in three families were collected from decomposing leaves in benthic area of stream pools. During experiment, 142 µl^-1 cells representing 11 taxa in 10 families were observed in litter bags. The colonization of epiphytic diatom was rapid in early stage of litter decomposition. The higher number of colonization made by Asterionella and Stenopterobia found in litter bags of all experimental weeks. These findings suggest that the rapid microbial colonization (ephiphytic algae) was occurred in the early stage of litter decomposition in an intermittent tropical stream and a comprehensive ecological investigation in perennial natural streams in India is needed.