Factors governing longitudinal variation in benthic macroinvertebrate fauna of a small Vindhyan river in Central Highlands ecoregion (central India)

摘要

Variation in the taxonomic composition of benthic macroinvertebrate fauna was examined in the Paisuni river at four stations (P1 to P4) located longitudinally along the river, with P1 being nearest the source of origin. The fauna was dominated by insects at all the stations. Total density increased from P1 to P3, decreased at P4 and differed significantly among the stations. Increase in the relative abundance from P1 to P4 was observed for Baetidae, Chironomidae and Gomphidae, and a decrease for Leptophlebiidae, Heptageniidae, Neoephemeridae, Rhyacophilidae and Thiaridae. Ordination analysis indicated that Rhyacophilidae was the characteristic taxon at P1, Thiaridae at P2 and Chironomidae at stations P3 and P4. Ordination also revealed that current velocity, substratum and landuse were the major environmental factors influencing the relative composition of macro-invertebrates. The longitudinal variation in taxonomic composition and assemblages showed a change of trophic status due to direct human interference at P2. Collectors were abundant at all stations but predominated the assemblages from P3 to P4. The balance between collectors, scrapers and predators shifted to predominance by collectors indicating heterotrophic conditions at P3 and P4 in contrast to autotrophic conditions at P1 and P2. Hence, two ecological zones are evident in the Paisuni river.