Rhynchospora croatanensis

Rhynchospora croatanensis , a new species from the outer Coastal Plain of North Carolina Primary authors:Patrick D. McMillan and Richard J. LeBlond

Known from a single collection in Croatan National Forest, this distinctive member of Rhynchospora sect. Rariflorae (Gale) McMillan adds another species to the endemic-rich flora of the Cape Fear Arch region of the Carolinas ( McMillan 2007). The plant is clearly related to R. rariflora (Michx.) Elliott and R. stenophylla Chapm. but differs from both by several characters of the inflorescence. This plant has been referred to as Rhynchospora sp. 2 in McMillan (2007) and as “ Rhynchospora species 1 ” in LeBlond (2023).

Rhynchospora croatanensis LeBlond & P. D. McMillan, sp. nov. ( Fig. 7 View FIG ). TYPE: U.S.A. NORTH CAROLINA. Croatan Co.: in

Croatan National Forest Compartment 28, in wet ecotone of old growth longleaf pine forest and pocosin on Carolina bay rim

northeast of Pringle Road at 2.0 mi N of NC 24, 20 May 1990, R . J . LeBlond 4676 (HOLOTYPE: NCU) .

Diagnosis.— Rhynchospora croatanensis differs from both R.rariflora and R.stenophylla primarily by having longer and wider achene bodies and tubercles, and more consistently aristate scales.

Description.— Plants perennial, short-rhizomatous. Culms erect, 10–30 cm long × 0.3–0.6 mm wide. Leaves filiform, involute, long-tapering to trigonous tip, shorter than culms, 0.2–0.4 mm wide. Flower clusters 1–2(–3), few-flowered, the spikelets on capillary branches to 10 mm long. Spikelets brown to tan, 1-fruited, 3–5 mm long, lanceoloid to broadly lanceoloid, acuminate. Fertile scales broadly lanceolate to broadly ovate, 2.7–3.5 mm long, acute to acuminate, and mostly short-aristate. Perianth bristles 6, antrorsely barbed, 0.81–1.41 mm (avg. 1.18 mm) long, from 0.53–0.91 (avg. 0.72)× as long as achene body, sparsely setose proximally. Achene body obovoid, lenticular, prominently transversely rugulose with 11–14 vertical striae of narrow rectangular alveolae, 1.40–1.80 mm (avg. 1.61) long × 1.20–1.65 mm (avg. 1.42) wide, 1.07–1.28× as long as wide. Tubercle triangular-subulate, 0.79–1.53 mm (avg. 0.96) long × 0.81–1.20 mm (avg. 1.03) wide; basal ¼ of tubercle setulose-margined.

Discussion.— In vegetative features and overall stature, Rhynchospora croatanensis is very similar to R. rariflora , but it consistently displays a single achene per spikelet and larger achenes, slightly longer bristles, and much longer tubercles. The single achene per spikelet is a feature it shares with R.stenophylla . It lacks the sterile fusiform spikelets characteristic of R. stenophylla , and has shorter culms, larger achenes, longer tubercles and shorter perianth bristles. The tubercle of R. croatanensis is significantly longer and wider than in R. rariflora and R. stenophylla (see Table 2).

The species of sect. Rariflorae are keyed as follows:

1. Fertile scale usually aristate;achene body 1.4–1.8 mm long × 1.2–1.65 mm wide; tubercle 0.8–1.55 mm long, 0.8–1.2

mm wide at base _____________________________________________________________________ Rhynchospora croatanensis 1. Fertile scale r arely aristate;achene body (1) 1.2–1.6 mm long × 0.9–1.3 mm wide;tuber cle (0.3) 0.4–0.95 mm long,

0.65–0.95 mm wide at base.

2. Achenes (1)2–4 per spikelet;st erile fusiform spikelets absen t to rare; fertile scale o vate,apex acute to rounded,

1.8–3.2 mm long; per ianth bristles 0.35–1.15 mm long, 0.25–0.8 × as long as achene body; tubercle triangular,

(0.3) 0.4–0.75 mm long, 0.65–0.95 mm wide at base____________________________________________ Rhynchospora rariflora

2. Achenes 1 per spikelet;sterile fusiform spikelets often abundant;fertile scale lanceolate,apex acute to acuminate,

3.5–4.5 mm long; perianth bristles 2.1–2.65 mm long,1.4–1.7× as long as achene body;tubercle triangular-subulate,

0.75–0.95 mm long, 0.65–0.75 mm wide at baseq _________________________________________ Rhynchospora stenophylla