Arkansas

Castanea, Jun 2002 by Singhurst, Jason R, Holmes, Walter C, Baldridge, Robert S

Spiranthes magnicamporum Sheviak. (ORCHIDACEAE)Little River County: Ark. Hwy 108, 1.3 mi SW of Foreman, limestone quarry area between N 33.70350, W 94.41367 and N 33.68145, W 94.44295, 17 Oct 1999, Holmes 10720, Singhurst, and Baldridge (BAYLU, UARK); Sevier County: White Cliffs on Ark. Hwy 317, ca. 2.3 mi SSE of Brownstown, N 33.74175, W 94.16909, 17 Oct 1999, Holmes 10730, Singhurst, and Baldridge (BAYLU, UARK).

Significance. The following collections are distribution records not included in the Annotated List of the Vascular Plants of Arkansas (Smith 1988) or Keys to the Vascular Plants of Arkansas (Smith 1994) and represent the first specimen documentation of this species in Arkansas. Although recorded in the Element Occurrence Record (Arkansas Natural Heritage Program), no voucher has been located. This record was based on a photograph of this species by Carl Slaughter in 1992 from Washington County, Arkansas.

Spiranthes magnicamporum Sheviak (Great Plains ladies tresses) is widely distributed in tallgrass prairies of the Midwest, with populations in prairie remnants from Ohio east to Pennsylvania south to Georgia and west to New Mexico (Liggio and Liggio 1999). Collection sites of the Arkansas specimens on exposed limestone rock outcrops adjacent to and in disturbed banked roadsides are similar to those described by Sheviak (1991), Diggs et al. (1999), and Liggio and Liggio (1999).

Spiranthes magnicamporum may be misidentified as S. cernua in herbaria due to the degradation of morphological characters described by Sheviak (1991) and Diggs et al. (1999). Our experience has shown that a field drawing of the lip of a fresh, mature flower facilitates identification. These two species differ in chromosome number and ecological requirements and are partially genetically isolated (Sheviak 1991). Regular disturbance (e.g., grazing and mowing) of vegetation on open limestone and calcareous outcrops probably helps maintain this species within its rather restricted habitat (Liggio and Liggio 1999).

We thank the following persons for searching collection/herbaria records and providing other valuable information regarding this species: Charles Sheviak (NYS), Johnnie Gentry (UARK), Theo Whitfield at the Arkansas Natural Heritage Program, George Johnson (APCR), George Yatskievych (MO), Dale Thomas (NLU), and Tom Wendt (TEX).-JASON R. SINGHURST, TEXAS PARKS AND WILDLIFE DEPARTMENT, WILDLIFE DIVERSITY PROGRAM, AUSTIN, TEXAS 78704 and WALTER C. HOLMES and ROBERT S. BALDRIDGE, DEPARTMENT OF BIOLOGY, BAYLOR UNIVERSITY, WACO, TEXAS 76798-7388.

LITERATURE CITED

DIGGS, G.M., B.L. LIPSCOMB, and R.J. O'KENNON. 1999. Shinner's and Mahler's illustrated flora of North Central Texas. Botanical Research Institute of Texas, Fort Worth.

LIGGIO, J. and A.O. LIGGIO. 1999. Wild orchids of Texas. University of Texas Press. Austin.

SHEVIAK, C.J. 1991. Morphological variation in the compilospecies Spiranthes cernua (L.) L. C. Rich.: ecologically-limited effects of gene flow. Lindleyana. 6:228-234.

SMITH, E.B. 1988. An atlas and annotated list of the vascular plants of Arkansas, 2nd ed. Published by the author, Fayetteville, Arkansas.

SMITH, E.B. 1994. Keys to the flora of Arkansas. University of Arkansas, Fayetteville. Received March 15, 2001; Accepted October 31, 2001.