Aquatic insect diversity in a tropical Vietnamese stream in comparison with that in a temperate Korean stream

A comparative investigation on aquatic insect diversity was conducted in a tropical stream in Southeast Asia (the Dak Pri stream in southern Vietnam; stream orders II-V, two sites per stream order) with a reference temperate stream in Northeast Asia (the Gapyeong stream in central Korea) in March 2001 and April 2000, respectively. The numbers of aquatic insect taxa in Dak Pri stream (268 species, mostly undescribed, 230 genera, 91 families, and 9 orders; 110.5 ± 17.1 species per site) were about twice those in Gapyeong stream (133 species, 98 genera, 51 families, and 8 orders; 60.3 ± 8.5 species per site). Coleoptera, Trichoptera, Ephemeroptera, and Diptera were the major aquatic insect orders with high taxonomic richness, and Coleoptera, Odonata, and Hemiptera contributed to the higher degree of aquatic insect diversity in Dak Pri stream. The species diversity indices of Dak Pri stream (4.37 ± 0.19) were higher than those of Gapyeong stream (3.73 ± 0.42), whereas the dominance indices of Dak Pri stream (0.195 ± 0.046) were lower than those of Gapyeong stream (0.346 ± 0.113). Collector-gatherers were predominant in both streams; shredders were more abundant in Dak Pri stream while scrapers were more abundant in Gapyeong stream. Factors affecting the higher degree of aquatic insect diversity in Dak Pri stream are discussed.