Rheophilic Macrozoobenthos Communities of the Southern Himalayas

Abstract

The regional diversity of rheophilic macrozoobenthos communities in North India and Nepal has been studied based on material collected from 450 original quantitative samples in 160 small and large watercourses within the altitude gradient of 200–2800 m above sea level. A total of 22 types of communities from 5 classes are identified: rhithral (hard substrates at rapid flow), crenal (mosaic substrates of small watercourses), pelal (soft sediments), phytal (macrophyte beds), and rhipal (mosaic substrates of river bank edge). Many of the community types occur in different altitudinal temperature zones, but their composition and structure vary as the study proceeds further into the mountains. It has been shown that oriental tropical taxa dominate the lowland tropical zone, endemic subtropical taxa dominate the mid-mountain zone, and Palearctic (Central Asian) groups dominate the high-mountain zone. The key features of tropical rheophilic communities are described in comparison with temperate zone communities. The application of the Ramensky–Grime classification of ecological strategies to macrozoobenthos communities is discussed.