In 1952, Moore and Rigney (1) recognized three subspecies of Etheostoma (Poecilichthys) radiosum (orangebelly darter): E.r. radiosum in the Ouachita and Little River systems, Arkansas and Oklahoma; E.r. paludosum in the Kiamichi and Clear Boggy systems, Oklahoma; and E.r. cyanorum in the Blue River system, Oklahoma. Moore and Rigney (1) specifically indicated the known range of E. radiosum as extending "westward to the Clear Boggy and Blue rivers in southern Oklahoma". Scalet (2), Echelle et al. (3), Echelle et al. (4), and Scalet and Platania (5) also describe the range of E. radiosum to be from the Blue River, Oklahoma east to the Ouachita system, Arkansas.
Here we report the discovery of four substantial populations of E. radiosum in tributaries of the Washita River (now part of Lake Texoma) in Oklahoma, southwest of its generally accepted range (1-5). We also call attention to an overlooked earlier record of E. radiosum in a tributary of the Washita River.
On 15 June 1985, with the fish ecology class of the University of Oklahoma Biological Station, we collected 17 darters from a flowing riffle on Little Glasses Creek, an intermittent stream ca. 3 km NNE of Kingston, in the NW 1/4, Sec. 20, T6S, R6E, Marshall County, 100 m downstream from a county road bridge (WJM 1804). Of these, six were "pure" or nearly pure E. radiosum, three were pure or nearly pure Etheostoma spectabile (orangethroat darter), and eight were considered putative hybrids E. radiosum x spectabile on the basis of characters of coloration detailed by Echelle et al. (6). The putative hybrids exhibited a full range of characteristics suggested to indicate backcrossing with parental individuals. These two darter species are well known to hybridize in many locations (6), so that the finding of so many putative hybrids in this riffle is not surprising. In the next riffle, ca. 200 m downstream and separated from the first riffle by a deep pool, a simple mark and recapture suggested presence of more than 500 E. radiosum, E. spectabile, or hybrids. Of 132 individuals taken on a recapture date (15 July 1985), 56% were pure or nearly pure E. radiosum.
Subsequent to discovery of the Little Glasses Creek population WJM and FPG searched several other tributaries of the Washita River and found three additional populations on 15 August 1985. In Rock Creek at the State Highway 22 bridge, Sec. 2 & 11, T5S, R7E, Johnston County, we collected 12 E. radiosum (WJM 1921) from a long, isolated pool with muddy water and a gravel-bedrock bottom. The habitat was quite different from the flowing, clear water habitat typical for this species; other darters taken in this collection were Etheostoma gracile (slough darter) and Percina macrolepida (bigscale logperch). From Butcher Pen Creek at State Highway 22 bridge, Sec. 4 & 9, T5S, R7E, Johnston County (WJM 1922), we collected 31 E. radiosum from clear water, isolated pools, kick setting in limestone gravel and rubble. No other darters were collected at this site. In a tributary of Glasses Creek on a county road in Sec. 3, T6S, R6E, Marshall County (WJM 1923) we took 37 E. radiosum along with several P. macrolepida in an isolated pool having a limestone rubble and mud bottom.
Etheostoma radiosum was reported once previously (in 1959) in the Washita system by Riggs and Bonn (7) from Butcher Pen Creek, Johnston Co., on the basis of four specimens, but this record was apparently overlooked by subsequent authors (2-5). The four E. radiosum are, however, not housed in the fish collection of the Stovall Museum, University of Oklahoma, to which Riggs (pers. comm.) donated most material of interest. Thus, the newly collected
Proc. Okla. Acad. Sci. 66:39-4 (1986)
specimens are apparently the only extant series from the drainage.
Addition of E. radiosum to the Washita River drainage is significant, not merely as a range extension, but potentially to the systematics of this complex species. According to Moore and Rigney (1), E. radiosum differs at the subspecific level in the different drainages it occupies. The most parsimonious expectation would be that E. radiosum in the Washita drainage are most like E.r. cyanorum of the Blue River, the geographically closest conspecific populations. However, preliminary examination of 20 E. radiosum from the Washita drainage populations discounts this prediction. Washita drainage E. radiosum averaged 11.25 (std. dev. = 4.12) unpored lateral line (LL) scales, compared to an average of only 4.86 (std. dev. = 2.64) for 15 Blue River specimens we examined. Washita material averaged 43.90 pored LL scales (std. dev. = 4.59) versus an average of 50.07 (std. dev. = 3.97) for Blue River specimens. On the basis of both these scale counts, which Moore and Rigney considered important in defining E.r. cyanorum, specimens from the Washita drainage are more similar to either E.r. paludosum or E.r. radiosum of drainages further east than to the Blue River subspecies.
The present evidence, although preliminary, suggests that the form in the Washita drainage will require careful evaluation before a trinomial is applied. The present note makes known the existence of E. radiosum in the Washita River system of southern Oklahoma. A detailed analysis of all subspecies of E. radiosum, including material from the Washita system, is now in progress. Upon completion of the study, all new material will be deposited in the Stovall Museum of the University of Oklahoma.
We thank Robert C. Cashner for critically reading the manuscript.
1. G.A. Moore and C.C. Rigney, Copeia 1952: 7-15 (1952).
2. C.G. Scalet, Life History of the Orangebelly Darter Etheostoma radiosum cyanorum (Osteichthyes: Percidae), Ph.D. Dissertation, University of Oklahoma, Norman, 1971.
3. A.A. Echelle, A.F. Echelle, M.H. Smith, and L.G. Hill, Copeia 1975: 197-204 (1975).
4. A.A. Echelle, A.F. Echelle, and B.A. Taber, Syst. Zool. 25: 228-235 (1976).
5. C.G. Scalet and S.P. Platania, Etheostoma radiosum (species account), in: D.S. Lee et al. (Eds.), Atlas of North American Freshwater Fishes, North Carolina State Museum of Natural History, 1980, pp. 685.
6. A.A. Echelle, J.R. Schenck, and L.G. Hill, Am. Midl. Nat. 91: 182-194 (1974).
7. C.D. Riggs and E.W. Bonn, Southwest. Nat. 4: 157-168 (1959).