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Page 35 ï~~1999 THE MICHIGAN BOTANIST 35 REDISCOVERY OF RHYNCHOSPORA (PSILOCARYA) NITENS (CYPERACEAE) IN THE GREAT LAKES REGION. A.A. Reznicek University of Michigan Herbarium North University Building Ann Arbor, Michigan 48109 Rhynchospora nitens (Vahl) A. Gray is a sedge of primarily southern coastal plain distribution in the United States, occurring eastwards from Texas along the Gulf coastal plain, and then northwards along the Atlantic coastal plain to Massachussets. It has also been recorded as a coastal plain disjunct in the Great Lakes region in northwest Indiana (Pepoon, 1927; Peattie, 1930; Deam 1940). Southward, R. nitens occurs in the tropics through the Caribbean and into Central America (Thomas, 1994). Rhynchospora nitens and related annual species such as R. scirpoides (Torr.) Griseb. and the primarily tropical R. eximia (Nees) Boeck. have in the past sometimes been recognized as the genus Psilocarya (Fernald, 1950; Voss, 1972; Swink & Wilhelm, 1994), but almost all authors now subsume them into a more broadly circumscribed Rhynchospora (Tucker, 1987; Bruhl, 1995; Goetghebeur, 1998). Rhynchospora nitens, however, is very rare in the northern portions of its range. In New England, it was rediscovered after a hiatus of half a century (Sorrie 1977), and there had been only one prior collection. In the Great Lakes region, until this discovery, it was last recorded in 1899 in Porter County, Indiana and thought to be "now possibly extirpated in the Chicago region" (Swink & Wilhelm, 1994). It was then one of only two species of coastal plain disjuncts in the Great Lakes region that had not been collected in this century, the other being Limnobium spongia (Bosc) Steud. (Reznicek, 1994). The species was rediscovered in the Great Lakes region, and also added to the flora of Michigan on 18 August 1999 at Goose Lake in Allegan County. The summer and fall of 1999 provided an excellent opportunity for searching for plants occurring on drawn down lake and pond shores, including many coastal plain disjuncts, because of the generally low water levels throughout the Great Lakes region. Goose Lake, like some other small, very shallow, and nearly flatbottomed lakes, was completely drawn down, the bottom being a peaty and sandy meadow dominated by species characteristic of such draw down habitats, including extensive, colorful stands of Rhexia virginica L., Panicum spp., Polygonum spp., Rhynchospora macrostachya A. Gray, and R. capitellata (Michx.) Vahl, and numerous other forbs and graminoids. Rhynchospora nitens was abundant in the central areas of the lake bottom, forming a continuous colony acres in size with many thousands of plants. At this site, R. scirpoides (Reznicek 10967, MICH) was also present and reasonably frequent, but occurred primarily around the margin of the lake and less commonly throughout the lake bottom. A number of other similar sites in southwestern Michigan were examined after this
Page 36 ï~~36 THE MICHIGAN BOTANIST Vol. 38 36 THE MICHIGAN BOTANIST Vol. 38 FIGURE 1. Achenes of Rhynchospora nitens (left) and R. scirpoides (right), from Reznicek 10966 and 10967 (MICH) respectively. The scale bar represents 0.5 mm. discovery, ranging north to Oceana County, and although R. scirpoides was locally frequent in suitable habitats, no other stations for R. nitens were discovered. Considerable searching, both in New England and in the Great Lakes region, has confirmed that the species is indeed very rare in the north, though one possible confounding factor in its recognition is similarity to the much more common and widespread Rhynchospora scirpoides. Superficially, these two species of generally similar habitat are essentially identical in appearance although, like Sorrie (1977), I noted that the spikelets of R. nitens had a subtle greyish cast to them (caused by a wider hyaline margin to the scale apices) that helped differentiate them from the dark brown spikelets of R. scirpoides. However, a quick examination of the achene tubercles will easily separate the two species. The tubercles of R. nitens are short, less than 0.5 mm long, distinctly broader than long, and abruptly contracted into the promptly deciduous style. Those of R. scirpoides are much longer, conspicuously longer than wide, and gradually tapered into the more or less persistent style. These differences are visible in the field with the naked eye or a low power hand lens. The achenes of R. nitens are also strongly transversly rugose, much more so than the nearly smooth achenes of R. scirpoides (Fig. 1). When they are just reaching maturity, the achenes of R. scirpoides also show a conspicuous pale border that is absent on the achenes of R. nitens.
Page 37 ï~~1999 THE MICHIGAN BOTANIST 37 SPECIMEN CITATION MICHIGAN. ALLEGAN Co.: Allegan State Game Area, Goose Lake, N of 130 Ave. and W of 38th St., SEX section 14, T3N R14W, ca 8 mi. NNW of Allegan. A.A. Reznicek 10966, F.W. Case, M. Penskar, 18 August 1999. (GH, MICH, MSC, NY, US, VDB, WIS). ACKNOWLEDGMENTS I am grateful to Fred Case and Mike Penskar for joining me in the field and helping look for these coastal plain disjuncts. I am also grateful to Bev Walters for taking the achene SEM photos. LITERATURE CITED Bruhl, J.J. 1995. Sedge genera of the world: relationships and a new classification of the Cyperaceae. Australian Systematic Botany 8:125-305. Deam, C.C. 1940. Flora of Indiana. Department of Conservation, Indianapolis. 1236 pp. Fernald, M.L. 1950. Gray's Manual of Botany. Ed. 8. American Book Co., New York. lxiv + 1632 pp. Goetghebeur, P. 1998. Cyperaceae. pp. 141-190 in The Families and Genera of Vascular Plants IV. Flowering plants. Monocotyledons. Alismatanae and Commelilianae (except Gramineae). Ed. K. Kubitzi. Peattie, D.C. 1930. Flora of the Indiana Dunes. Field Museum, Chicago. 432 pp. Pepoon, H.S. 1927. Flora of the Chicago Region. Chicago Academy of Sciences, Chicago. xxii + 554 pp. Reznicek A.A. 1994. The disjunct coastal plain flora in the Great Lakes region. Biological Conservation 68: 203-215. Sorrie, B.A. 1977. Rediscovery of Psilocarya nitens in New England. Rhodora 79: 163-164. Swink, F. & G. Wilhelm 1994. Plants of the Chicago Region. Ed. 4. Morton Arboretum, Lisle, Illinois. xiv + 921 pp. Thomas, W.W. 1994. Rhynchospora pp. 404-422 in Flora Mesoamericana. Vol. 6. Alismataceae a Cyperaceae. Tucker, G.C. 1987. The Genera of Cyperaceae in the southeastern United States. Journal of the Arnold Arboretum 68: 361-445. Voss, E.G. 1972. Michigan Flora, Part 1. Gymnosperms & Monocots. Cranbrook Institute of Science, Bloomfield Hills, Bulletin Number 55 & University of Michigan Herbarium xiv + 488 pp. ANNOUNCEMENT Checklist of the Vascular Plants of Wisconsin. July, 2001. The Wisconsin Department of Natural Resources and the University of Wisconsin-Madison Herbarium announce the publication of this volume, authored by Mark A. Wetter, Theodore S. Cochrane, Merel R. Black, Hugh H. Iltis, and Paul E. Berry and available at no cost from the Wisconsin DNR, Technical Bulletin No. 192, paperback. For a free copy, contact the Bureau of Integrated Science Services Research Center, 1350 Femrite Drive, Monona, WI 53716. Telephone 608. 221. 6320; fax 608. 221. 6353.