Rhynchospora stiletto (Cyperaceae), a new species of beaksedge from the southeastern U.S.A

Summary Rhynchospora stiletto Naczi & Ciafré (Cyperaceae), a new species from the southeastern U.S.A., is described, illustrated, and compared with morphologically similar species. It is unique among species of Rhynchospora sect. Rhynchospora by having very long tubercles. Additionally, it is distinguished by the combination of 1-flowered spikelets, turbinate glomerules, dark brown scales, and relatively wide fruits. Images are provided of its various habitats, all of which are sunny, wet, and calcium-rich but otherwise nutrient-poor. It occurs in the Ozark Highlands, Interior Plateau, and Ridge and Valley ecoregions of the southeastern U.S.A. A conservation status of Vulnerable appears to be appropriate for R. stiletto because it is a specialist of rare, small-patch habitats, has a very small area of occupancy, and is known from only seven localities.