Jan Jeffrey Hoover
U.S. Army Engineer Waterways Experiment Station, ER-A, 3909 Halls Ferry Road, Vicksburg, MS 39180* and Appalachian Environmental Laboratory, University of Maryland, Frostburg, MD 21532.
Surveys of the aquatic insects of Oklahoma have focused on the central and southern portions of the state. Faunas there are moderately species-rich, but chironomid diversity varies. Taxonomic richness of larval midges may be lower than 15 taxa (1, 2), moderate with 20-30 taxa (3, 4), or high with more than 30 taxa (5, 6). Chironomids are poorly known from the Ozark region of Oklahoma, however, an area of considerable interest to aquatic ecologists because of the taxonomic richness of other groups such as fishes (7). During the period 22 April26 May 1986, I surveyed larval midges from waters in the northeast part of the state.
Thirty sites representing a variety of aquatic habitats were sampled in Adair, Cherokee, and Delaware counties. Locations included Luna Branch, Fourteen Mile Creek, Peacheater Creek, Flint Creek, Spring and Double Spring Creeks, and several springs. Stream width ranged from < 1 m to 50 m. Chironomids were sampled by dipnetting and kicknetting in all microhabitats and by picking from overturned rocks and logs for 30 min. Depth of capture ranged from 10 cm to 150 cm. Specimens were preserved in 70% ethanol with 5% glycerin, and subsequently mounted on slides and cleared with CMC-10. Standard taxonomic references were used for identification (810). Since most North American genera contain species which are undescribed or for which distinguishing larval characteristics are unknown, many identifications are to genus, subgenus, or species group level (10).
Thirty-three taxa were identified (Table 1), over a third of which had not been listed in previous surveys within the state (1-6, 11, 12). Several taxa were abundant and/or frequent and might be considered characteristic for this region. A tanypodine of the Thienemannimyia group appeared monospecific and keyed out to the genus Conchapelopia (10). It was the most frequently encountered and second most abundant midge collected, with larger numbers found in deeper water. Dicrotendipes neomodestus was the most abundant and a frequently collected taxon. Species of Dicrotendipes typically inhabit lakes (4, 10, 12, 13), but in this study D. neomodestus was numerous in shallow water of small streams.
Chironomus spp. were commonly encountered but usually in low numbers. A cut-off pool at the confluence of Flint Creek and the Illinois River, however, contained large numbers of a species conforming to C. staegeri (14). The pool was silty, turbid, and probably hypoxic since the stoneroller minnows (Campostoma anomalum) trapped in it were skimming the surface film. The genus Polypedilum was common and was dominated by two species, P. convictum and P. aviceps, the latter of which was most abundant in small streams. The genera Stictochironomus, Cryptochironomus, Eukiefferiella, Cricotopus, and Paratendipes were common. All five genera contain a large number of undescribed species (10) but in this study, only the last two were obviously polyspecific.
The chironomid fauna of northeast Oklahoma is distinctive from that of previously surveyed systems in the state, including that of an adjacent county (11). In other studies of Oklahoma midges, Chironomini averaged 62% of the taxa, compared with 36% in this study. Many taxa that I collected were not reported in previous studies. Distinctiveness of the Ozark fauna may be attributed to the habitats and areas sampled in earlier studies. Previous work focused on larger streams (1-3, 5, 6) and reservoirs (4, 11, 12), rather than smaller, headwater streams where Orthocladinae and Tanypodinae would be more likely to codominate with Chironomini. Also, previous studies were not conducted within the Ozark uplift, a geologically stable area that has remained above sea level since the late Palaeozoic (15) and which represents the western limits of distribution for many eastern species (7, 16).
This study was funded by a summer research assistantship from the Oklahoma Biological Survey while I was a graduate student in the Department of Zoology, University of Oklahoma. Ken and Jan Spencer and Bryan and David Morrison provided accommodations and other valuable help. Chip Morrison assisted in the field. Identifications were confirmed by C. Rex Bingham and comments on an earlier manuscript made by W. J. Matthews, W. B. Richardson, and B. C. Cowell. Many thanks to all of the above. This is contribution number 2159 from the University of Maryland Appalachian Environmental Lab.
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