7840 - Laserfiche WebLink

Home Browse Search

218 GREAT BASIN NATURALIST [Volume 55 process continued until N was less than the number of samples already processed for the taxon. Because of time and financial constraints, we never picked more than 30 samples for any specific habitat and sample date. All sorted samples were preserved in 70% ETOH, Chironomids were removed from 70% ETOH and placed in distilled water for 10-15 min prior to clearing. Individual specimens were placed in hot (z80oC) 10% KOH (Cranston 1982) for 5-15 min to clear (larger specimens required more time to clear). After clearing, specimens were transferred to distilled water for at least 5 min. Each specimen was then placed in glycerine on a microscope slide for identification. Only late instars were identifi- able. Representative specimens of each genus encountered were permanently mounted. Specimens were classified to the generic level using keys by Mason (1968), Wiederholm (1983), and Merritt and Cummins (1984). Data Analysis Average densities (# 1m2) and 95% confi- dence limits for each of the four main taxa and each genus of Chironomidae were calculated for each sample site and date. Because density distributions were contagious, 95% confidence intervals were calculated for each of the four main taxa using a logarithmic transformation suggested by Elliot (1977; Tables 2-5). These values were then applied to the arithmetic mean (Shiozawa and Barnes 1977). Confidence inter- vals were not calculated for each genus in the Chironomidae because densities of some genera were too low. Cluster analysis was performed using the statistical package NTSYS-pc (Rohlf 1992). Several dissimilarity measures, including Bray- Curtis, Canberra s, and Renkonen's, were used to generate distance matrices, A comparison of each of these matrices to the original data showed that the Bray-Curtis measure (Bray and Curtis 1957) provided the best "fit" of the cluster analysis to the data. Average linkage clustering of the Bray-Curtis distances, based on the mean number of individuals/m2 of each species between habitat types and sample dates, was done with the unweighted pair-group method using arithmetic averages (UPGMA; Krebs 1989), RESULTS Invertebrates Nematodes occurred in every sample pro- cessed and were most abundant in the July sample of the ephemeral side channel habitat (302,603/m2) and least abundant in the river channel August sample (2421/m2; Tables 2-5). They comprised the majority of benthic inver- tebrates in all habitats and sample dates except TABLE 6, Functional group (Merritt and Cummins 1984) and habitat association of Chironomidae genera from the Green River, Ouray National Wildlife Refuge, Ouray, UI Functional group Taxon Collectors Predators Shredders Unknown Habitat association * Ablabesmyia X SIW Chironomus X RC,ESC,RB,SIW Cladotanytarsus X RC,ESC,RB,SIW Cricotopus X X SIW Cryptochironomus X ESC,SIW Cryptotendipes X ESC,SIW nr. Cyphomella X RC Glyptotendipes X X SIW r, Microtendipes X SIW Paramerina X RC Paratanytarsus X SIW Paratendipes X RC Polypedilum X X X RC,ESC,RB,SIW Procladius X X RC,ESC,RB,SIW Psectrocladius X X RC,RB,SIW nr, Stempellinella X RC Tanypus X X ESC,SIW Tanytarsus X RC,ESC,RB,SIW Zavrelia X SIW *RC = river channel, Ese = ephemeral side channel, RB = river backwater, SIW = seasonally inundated wetland.