HABITAT SEPARATION AMONG CHIRONOMIDAE (DIPTERA) IN BIG-SPRINGS

Habitat separation among Chironomidae was determined for five habitats in Big Springs, which is located in the high plains of western Kansas . Larvae, pupae, pupal exuviae and adults were qualitatively collected from each habitat on seven dates over a two-year period. The five hab itats investigated were: spring source, spring run, a large pool, spla sh zones, and saturated soils/small seeps. Sixty-six species occurred in the five habitats, with Chironomini being most species rich (31 spe cies), followed by Orthodadiinae (22), Tanypodinae (9) and Tanytarsini (4). The highest species richness was in the pool habitat (45 species ), which was dominated by Chironomini. Orthocladiinae dominated all ot her habitats, with the spring run having second highest species richne ss (20 species), followed by the spring source and splash zones (each with 13 species) and the saturated soils and seeps (11 species). Forty -eight of the species occurred in only one habitat and only three taxa , Tanytarsus spp., Corynoneura spp. and Thienemanniella spp., were fou nd in all five habitats. Jaccard's Coefficient showed that the composi tion of the splash zone and spring source, and the splash zone and spr ing run were most similar. However, an analysis of species composition using the Simple Matching Coefficient indicated that the splash zone and spring source were most similar, and the splash zone and saturated soils and seeps as second most similar. Both indices, however, indica ted that the spring source and the large pool had the least similar co mposition. These results suggest that patterns of longitudinal zonatio n in the composition of chironomids, and perhaps other macroinvertebra tes, along spring and spring run gradients are strongly influenced by physical variations in the microhabitats that occur as the groundwater discharge merges into a well defined stream with alternating pool-rif le habitats.