Dichanthelium freckmannii LeBlond, 2024

Weakley, Alan S., LeBlond, Richard J., McMillan, Patrick D., Sorrie, Bruce A., Poindexter, Derick B., Fuller, J. Brandon, Bridges, Edwin L., Budach, Brett J., Carr, Susan C., Crowl, Andrew A., Manos, Paul S., Fritsch, Peter W., Orzell, Steve L., Wipff, Joseph K., Messec, Lilly Anderson, Dellinger, Bob, Ungberg, Eric A., Yawn, Noah D., Cressler, Alan M., Oberholster, Chris, Barger, T. Wayne, Carter, J. Richard, Floden, Aaron J., Knapp, Wesley M., Copen, Iris, Jenkins, Amy M., Hughes, Ethan L., Annis, Jenna, Baker, Wilson & Mears, Randy L., 2024, Studies In The Vascular Flora Of The Southeastern United States. X, Journal of the Botanical Research Institute of Texas 18 (1), pp. 17-77 : 66-69

Dichanthelium freckmannii LeBlond , sp. nov. ( Fig. 22 ).

TYPE: U.S.A. NORTH CAROLINA: Onslow and Pender counties : Sandy Run Savannas State Natural Area ,in wet pine savanna habitat recovering from clear-cut, about 800 m N of Shelter Swamp Creek on the border of Onslow and Pender counties ,lat.34.61409, long.–77.63201, 6 Jun 2013, LeBlond 6960, Weakley, & Sorrie (HOLOTYPE: NCU; ISOTYPE: US) .

Diagnosis.— Dichanthelium freckmannii may be a hybrid of D. scabriusculum (Elliott) Gould & C.A. Clark and D. scoparium (Lam.) Gould , but the vernal spikelets are shorter than those of either of the putative parents, and the cauline leaves are fewer. Autumnal spikelets are longer and narrower than the vernal, a condition that has not been reported for the other two species.

Description.— Vernal culms 1-few, cespitose to short-rhizomatous, stout, 70–140 cm long, 1.5–2.5 mm wide at lowest elongate internode. Lower internodes moderately densely ascending papillose-pilose, medial and distal internodes becoming less densely pubescent with mixed orientation hairs 1–2 mm long. Nodes bearded with densely retrorse hairs 1–2.5 mm long at proximal nodes, hairs becoming 0.5–1 mm long on distal nodes. Winter rosette not seen. Basal leaf sheaths erect, their blades erect to retrorse, from 3.8–12.8 cm long × 4–12 mm wide. Cauline leaves 4–7. Sheaths shorter than internodes, moderately densely papillose-pilose with hairs 1–2 mm long of mixed orientation, becoming less dense on distal sheaths; collars densely pubescent; lower and mid-culm sheaths 3.5–9.5 cm long, distal-most sheath (of flag) 4.5–13 cm long.Ligules 1.2–3 cm long, densely ciliate, membranous portion 0.1–0.4 mm long. Blades linear-lanceolate, gradually tapered distally to acuminate-aristate apex, bases narrowly rounded to subcordate to truncate, 7–20 cm long × 5–10 mm wide, averaging more than 15× as long as wide; adaxial surface sparsely pubescent proximally, glabrate distally, the surface smooth to sparsely scabrous; abaxial surface moderately pubescent to moderately densely velvetypubescent; margins scabrous, eciliate to ciliate basally; uppermost blade (flag) 3.5–6 cm long × 4–6 mm wide. Peduncles 5.5–13.5 (–23.5) cm long when mature, moderately short pubescent. Panicles 7.5–14 cm long × 4.5–7 cm wide, averaging less than half as wide as long; rachis short-pubescent proximally, glabrate distally; branches glabrate and spreading-ascending to ascending; pedicels glabrous. Vernal spikelets 1.9–2.3 mm long, 0.9–1.0 mm wide, elliptic, acute, moderately densely puberulent with hairs 0.1–0.2 mm long; lower glumes 0.5–0.7 mm long, 1/2–1/3 as long as spikelet, ovate with rounded (-acute) apex; upper glumes and lower lemmas subequal, exceeding fertile lemma by about 0.2 mm; upper lemma 1.7–1.8 mm long × 0.7–0.8 mm wide. Autumnal culms branching from mid and especially upper nodes, the top-heavy culms sprawling over other vegetation. Primary (aestival) branching begins 35–75 cm above culm base. Fascicled leaves of secondary (autumnal) branches 1–3 cm long × 1.5–5 mm wide. Autumnal panicles hidden in the fascicles. Spikelets 2.2–2.5 mm long, 0.8–1.1 mm wide, longer and proportionately narrower than vernal spikelets.

Etymology.— The speci fic epithet honors Robert W. Freckmann, co-author with Michel G. Lelong of the Dichanthelium treatment in Flora of North America Volume 25 ( Freckmann & Lelong 2003). His extensive research while at the University of Wisconsin has greatly clarified and expanded our knowledge of this large and complex genus.

Additional collections: U.S.A. North Carolina. Onslow / Pender cos.: Sandy Run Savannas State Natural Area , in wet pine savanna habitat recovering from clear-cut, about 800 m N o f Shelter Swamp Creek on the border of Onslow and Pender counties , lat. 34.61409, long. –77.63201, 29 Oct 2014, LeBlond 7159 (PARATYPE: NCSC, NCU);76 Jun 2022, LeBlond 7189 ( PARATYPES: FLAS, MO, USCH) .

Distribution and ecology.— The type locality on the border of Onslow and Pender counties in North Carolina is currently the only known population of Dichanthelium freckmannii . Habitat is a fire-adapted wet pine savanna recovering from a circa-1980 clear-cut and surface disturbance, with the soil having a calcareous influence from a subterranean coquina limestone layer. The natural community has been classified as a Very Wet Loamy Pine Savanna by the North Carolina Natural Heritage Program. “These communities are very rare, with a limited and patchy geographic range. They often, maybe always, have inclusions where soils are high in calcium and have a higher pH (5.5 to 7.2), but the majority of their soil is similar to other pine savannas (pH 3.8–4.1)” ( Schafale 2023). The site is also the type locality for Scleria bellii , and associates include Rhynchospora thornei , Carex lutea , Coreopsis aristulata , Thalictrum cooleyi , Allium species 1 (sensu Weakley & Southeastern Flora Team 2023), Dichanthelium scoparium , D. scabriusculum and Scleria pauciflora Muhl. ex Willd. var. caroliniana Alph.Wood.

Discussion.— The stout, long sulcate culms, leaf blade length and subcordate bases, and top-heavy autumnal branching align this entity with Dichanthelium scoparium and D. scabriusculum , both of which occur at the site. It differs from both primarily by vernal spikelet length, in number of nodes per culm, and in having longer and relatively narrower autumnal spikelets. Several other characters can be used to separate D. freckmannii from the other two species individually, as in the following key.

KEY

1. Culm nodes glabr ous to puberulent;ligule an ecilia te membrane 0.5–1.3 mm long; blade abaxial sur face glabrous (-sparsely pubescent basally); peduncle scabr ous to smooth (r arely pubescent);panicle r achis glabrous,usually pellucid-punctate___________________________________________________________________ Dichanthelium scabriusculum

1. Culm nodes r etrorsely bearded; ligule densely cilia te, 0.5–3 mm long;blade abaxial sur face moderately to densely pubescent;peduncle moderately to densely short-pubescent;panicle rachis pubescent proximally,glabrate distally, not pellucid-punctate.

2. Lowest elongate internode 2.1–3.5 mm wide; cauline leaves 7–11; ligule 0.5–2 mm long; vernal culm blades 9–20 mm wide,averaging 10× or less as long as wide, adaxial surface densely soft-pubescent; vernal panicles 5–12 cm wide,more than half as wide as long when ma ture;vernal and autumnal spikelets 2.2–2.8 mm long × 1.3–1.5 mm wide,ovoid-ellipsoid to obovate,abruptly pointed; upper glume shorter than fertile lemma _______ Dichanthelium scoparium

2. Lowest elongate internode 1.6–2.5 mm wide; cauline leaves 4–7;ligule 1.2–3 mm long; vernal culm blades 5–10 mm wide,averaging 15× or more as long as wide,adaxial surface sparsely pubescent proximally,glabrate distally;vernal panicles 4.5–7 cm wide,less than half as wide as long when mature;vernal spikelets 1.9–2.3 mm long × 0.9–1.0 mm wide,ellipsoid,acute;autumnal spikelets 2.2–2.5 mm long× 0.8–1.1 mm wide,narrowly elliptic,acute to long-acute; upper glume exceeding fertile lemma __________________________________________________ Dichanthelium freckmannii

Figures

FIG. 22.Holotype of Dichanthelium freckmanii. Image by Shanna Oberreiter (NCU).