Rhynchospora setosa LeBlond

Rhynchospora setosa LeBlond & P. D. McMillan , sp. nov. ( Fig. 8 View FIG ). TYPE: U.S.A. MISSISSIPPI. Jackson Co.: DeSoto National Forest, in seepage slope in longleaf pine forest near Dogleg Bog along John Smith Road , 26 Sep 1996, R. J. LeBlond 4644 & B. A. Sorrie (HOLOTYPE: NCU) .

Diagnosis.— Rhynchospora setosa differs from R. chapmanii primarily by consistently present and long perianth bristles, longer and proportionately narrower achenes,and larger spikelet scales with longer awns (see Fig.9 View FIG ).

Description.— Plants perennial, cespitose. Culms erect to ascending, 15–55 cm long, 0.5–0.7 mm wide, obscurely trigonous. Basal leaves awl-shaped proximally, subulate distally, to 3.5 cm long × 1.7 mm wide. Culm leaves 6–8, 2.4–7.2 cm long × 0.3–1.2 mm wide, flat, margins finely serrulate. Inflorescence terminal, solitary, broadly turbinate to hemispheric, 0.6–0.8 cm long × 0.8–1.4 cm wide, subtended by several setaceous bracts to 2.4 cm long. Spikelets strictly ascending, ovoid-aristate, light brown to pinkish-tan, with one achene. Scales 2.2–2.7 mm long × 0.85–0.95 mm wide, narrowly ovate to ovate-lanceolate, margins inrolled 0.2–0.4 mm on a side, midrib excurrent as prominent awn 0.5–0.9 mm long. Bristles (3)4, antrorsely scabrous, all on one side of achene, 0.8–1.2 mm long, 0.67–1.0 × as long as achene body. Achene narrowly elliptic to elliptic, lenticular, body 1.2–1.6 mm long × 0.8–1.0 mm wide, pale brown to whitish, darker distally, basally smooth to minutely striate. Tubercle deltoid-apiculate, 0.28–0.40 mm long × 0.44–0.61 mm wide at base.

Discussion.— This beaksedge is very similar to Rhynchospora chapmanii (see Table 3) and is likely closely related. It differs primarily in the consistently present and long perianth bristles, longer and proportionately narrower achenes, larger spikelet scales that are characteristically rolled inwards for 0.2–0.4 mm on a side, and with a long excurrent aristate midrib. Spikelet and achene coloration also appear to differ, but the sample size is small.

The species of sect. Chapmaniae in the U.S. are keyed as follows. 1. Leaves with a short taper at the tip, blunt to acute,but not long-acuminate; achene surface minutely pitted near the margin. 2. Basal leaves 4–6 mm wide, ciliate,rosulate;scales acumina te, the midr ib ciliate; bristles 6, <½ the length of the achene ________________________________________________________________________________ Rhynchospora ciliaris 2. Largest basal leaves 2.5–3.0mm wide,eciliate,not rosulate;scales aristate,the midrib eciliate;bristles 3–4,1 or more equaling or exceeding the tubercle ________________________________________________________ Rhynchospora solitaria 1. Leaves long-acuminate at the tip; achene surface smooth or finely striate. 3. Bristles (3) 4,on one side of achene, 2⁄3 to as long as achene body; achene body 1.2–1.6 mm long × 0.8–1.0 mm wide __________________________________________________________________________________ Rhynchospora setosa 3. Bristles absent or 1–3 rudimentary;achene body either 1.0– 1.2 mm long × 0.8–1.0 mm wide or 1.4–1.8 mm long × 1.2–1.5 mm wide. 4. Inflorescence composed of (1–)2–3 turbinate to ellipsoid clusters;spikelets pale reddish-brown,(2.7–)3.0– 3.5 mm

long;achenes usually 2 per spikelet _________________________________________________ Rhynchospora brachychaeta 4. Inflorescence composed of 1(–2) hemispheric to broadly turbinate cluster(s);spikelets white to pale brown,either

2.0–2.5(–3) mm or (3.5–)4.0– 5.5 mm long; achenes 1 per spikelet.

5. Base of plant not bulb-like,not enclosed in bladeless sheaths;spikelets 2–2.5(–3) mm long; achene 1.0– 1.2 mm

long,0.8–1.0 mm wide_____________________________________________________________ Rhynchospora chapmanii

5. Base of plant bulb-like,enclosed in bladeless sheaths;spikelets (3.5–)4.0– 5.5 mm long; achene 1.4–1.8 mm long,

1.2–1.5 mm wide ____________________________________________________________________ Rhynchospora pallida

Distribution and ecology.— Rhynchospora setosa is currently known from a single population in the Gulf Coastal Plain of southern Mississippi. No other collections of this species were found during the examination of Rhynchospora specimens at the following herbaria: CHARL, CLEMS, DUKE, FMU, GA, GH, LCU, NY, NCU, P, UC, US, USCH and WILLI. The Mississippi plants were found in DeSoto National Forest on a seepage slope within a longleaf pine forest, with pitcher-plants prominent. This habitat is commonly known as a pitcher-plant bog or pitcher-plant prairie, occurring on sloping to nearly flat terrain. The natural community has been classified as a Seepage Meadow by NatureServe ( NatureServe Explorer 2024), with a range extending from western Florida Panhandle to Mississippi. Associates include Dichanthelium chamaelonche (Trin.) Freckmann & Lelong , D. nudicaule (Vasey) B.F. Hansen & Wunderlin , Xyris drummondii Malme , Rhynchospora macra (C.B. Clarke ex Britton) Small , Drosera tracyi (Diels) Macfarlane , Sarracenia alata (Alph. Wood) Alph. Wood , Scleria muhlenbergii Steud. , Liatris spicata (L.) Willd. var. resinosa (Nutt.) Gaiser , Carphephorus pseudoliatris Cass. , Aristida palustris (Chapm.) Vasey , and Lycopodiella appressa (Chapm.) Cranfill.

This species should be sought in similar habitat throughout the Gulf Coastal Plain. It is likely overlooked due to the similarity in appearance to the common and widespread Rhynchospora chapmanii . Though it is known only from this single occurrence, many other species associated with highly specific habitats, such as herb-dominated seepage slopes, are known from only a handful of locations, and some are only known historically and may be extirpated in the wild.