Arundinella namprikensis Suparna Saha, D. Maity, Arnab Banerjee, M.D. Dwivedi et D. Pradhan

Saha, Suparna, Banerjee, Arnab, Dwivedi, Mayank D., Pradhan, Durga K. & Maity, Debabrata, 2024, Novelty in Arundinella (Arundinelleae, Panicoideae, Poaceae): Morphological and Molecular Evidences for a New Species from Sikkim Himalaya, Phytotaxa 647 (3), pp. 274-286 : 279-285

Arundinella namprikensis Suparna Saha, D. Maity, Arnab Banerjee, M.D. Dwivedi et D. Pradhan , sp. nov. — Figs. 1–3

Arundinella namprikensis is morphologically most similar to Arundinella nepalensis Trin. (1826:62) but differs by its long smooth rhizome (vs. short scaly rhizome), glabrous culm nodes (vs. nodes appressed silky pubescent), leaf sheath densely ciliate along one margin only (vs. either both margins ciliate or both margins eciliate), up to 8 mm long pedicels (vs. up to 4 mm long), usually 5–7-veined lower glume with only midvein scabrid towards apex (vs. 3-veined and all veins scabrid), strongly 5–7-veined upper glume (vs. faintly 5-veined), always bisexual lower floret (vs. lower floret staminate or barren; rarely bisexual), 7-veined lower lemma (vs. 3–5-veined) and upper palea acute with few cilia (vs. minutely bifid, without cilia).

Arundinella namprikensis also shows resemblance with A. cochinchinensis specially in features such as: both leaf sheaths and leaf blades with tubercle-based hairs, 3–5 mm long spikelets, glabrous glumes and persistent 4–5 mm long awn, however, it can readily be distinguished from the latter by having smooth rhizomes, glabrous culm nodes, shorter ligule up to 0.5 mm high, loose panicle with mostly smooth central axis, loosely spiculate panicle branches never concealing central axis, 5–7-veined lower glume with midvein scabrid towards apex, 5–7-veined upper glume, 7-veined lower lemma and upper palea acute with few cilia. Most importantly always bisexual lower floret in A. namprikensis makes it sufficiently different from A. cochinchinensis where lower floret is always staminate.

Type:— INDIA. North Sikkim, towards river, after Chungthang, 1790 m, 2 September 2022, Saha, Maity, Halder, Ghosh, Midday & Mandal 25835 (Holotype: CUH; Isotypes: CAL, CUH) .

Perennial. Rhizomes long-creeping, up to 1.5 m, 3-6 mm across, woody, smooth, glabrous. Culms erect, often decumbent, simple, rare often branched, stout, up to 2 m tall, 2–5 mm across, 6–8-noded, terete, nodes smooth, glabrous, internodes glabrous. Leaf sheaths 6−18 cm long, 0.4–0.6 cm across, tuberculate-pilose along right margin (hairs up to 1.5 mm long), abaxially tuberculate-pilose, adaxially glabrous, mouth bearded with up to 7.5 mm long hairs. Ligule 0.3–0.5 mm high, truncate, fimbriolate. Leaf blades narrowly lanceolate, flat or convolute, 10–50 × 0.4–1.4 cm, apex long acuminate, margin scaberulous, tuberculate-hispid on both surfaces. Panicle open, 40–65 cm; central axis smooth, scabrid towards apex, strongly striate (striations wavy), nodes villous; branches many, slender, 2–20 cm, alternate, opposite, subopposite or whorled, loosely spiculate; lower branches with several branchlets, upper ones mostly simple; pedicels 1.2-8 mm long, scabrid. Spikelets paired, one long- and other short-pedicelled, 4–8 mm long, green, often purple tinged; lower glume ovate to narrowly ovate, 2.8–4 × 0.9–1.5 mm, apex acuminate, margin usually glabrous, rarely sparsely hairy, (4–)5–7-veined, midvein keeled, scabrid towards apex, rarely scabrid throughout, green to purple-tinged; upper glume ovate, (3.8–)4.2–5 × 1–1.5 mm, apex acuminate, 5–7-veined, sometimes veins with few hispid hairs and margins sparsely hairy, green to purple tinged. Florets 2; lower bisexual, longer than lower glume, unawned; upper bisexual, 2–2.5 × ca. 0.8 mm, awned, with a bearded callus; callus hairs 1/4–1/2 length of upper lemma; disarticulating below florets. Lower floret: lower lemma broadly ovate, boat-shaped, 3–4 × 1–1.6 mm, apex acute, margin usually glabrous, rarely sparsely hairy, (5-)7-veined, midvein somewhat keeled towards apex, glabrous, smooth, pale green with bright green veins; lower palea ovate, 2.5–3 × 0.8–0.9 mm, apex acute, margin infolded, ciliate, base auriculate (door-like flaps), 2-veined, 2-keeled, hyaline; auricles non-overlapping; keel ciliolate (-scabrid) towards apex; lodicules oblong-obovate, ca. 0.3 × 0.2 mm, apex truncate. Stamens 3; anthers oblongoid, 1–1.8 × 0.2–0.4 mm, yellow to purple; filaments 0.1–0.4 mm long, hyaline. Pistil 1; ovary ovoid, 0.2–0.4 × 0.1–0.2 mm; style 0.5–0.8 mm long; stigma 0.5–1.15 mm long, red-purple. Upper floret: upper lemma broadly elliptic, 2–2.2 × ca. 1 mm, apex usually retuse (-emarginate), sometimes one lobe attached with the awn, sometimes obtuse (then awn terminal), fimbriolate, subcoriaceous, granulose, faintly 3-veined, dull white, awned; awn from sinus, sometimes terminal, geniculate, (2-) 4–5 mm long, scabrid (except column), with (1-) 1.8–2 mm long brown twisted column; upper palea ovate to narrowly ovate, 2.3–2.4 × 0.5–0.6 mm, apex acute, margin auriculate (door-like flaps), 2-veined, 2- keeled, glabrous, granulate dorsally, hyaline; auricle obliquely obovate-spathulate, strongly overlapping; keel smooth, glabrous; lodicules oblong-obovate, ca. 0.3 × 0.3 mm, apex truncate, hyaline. Stamens 3; anthers oblongoid, 1–2 × 0.3–0.5 mm, yellow to purple at maturity; filaments 0.2–0.4 mm long, hyaline. Pistil 1; ovary ovoid, 0.2–0.7 × 0.15– 0.2 mm; style 0.3–0.9 mm long; stigma 1–1.4 mm long, red-purple to brownish. Caryopsis not seen.

Etymology —The specific epithet has been chosen after ‘Namprik’, a small village of North Sikkim, one of the type localities of the new species.

Flowering — May to October

Distribution and Habitat– Arundinella namprikensis has been collected from three localities of North Sikkim. Probably it is endemic to the state Sikkim. The species grows on rocky mountain slopes as well as dry sandy river banks in between 900–2200 m amsl commonly in association with Pogonatherum crinitum (Thunb.) Kunth ( Poaceae ), Neillia thyrsiflora D.Don ( Rosaceae ), Galium sp. ( Rubiaceae ), Selaginella sp. ( Selaginellaceae ), Boehmeria virgata var. macrostachya (Wight) Friis & Wilmot-Dear ( Urticaceae ), Elatostema sp. ( Urticaceae ), Pilea sp. ( Urticaceae ), Vitis sp. ( Vitaceae ), etc.

Paratypes — North Sikkim, Namprik, 6 June 2023, Saha, Maity, Halder & Mandal 26125; North Sikkim, before Chungthang, 19 August 2023, Saha, Maity, Halder, Ghosh & Mandal 26819 (CAL, CUH and SSFH).

Molecular diagnosis

A/G at position 189; C/T at position 440; A/G at position 458; INDEL of GC at Position 460-461; T/C at position 462; G/T at position 494; T/C at position 582. TreeBase link:http://purl.org/phylo/treebase/phylows/study/TB2:S31118?xaccess-code=568dccfaab414e957fb76a15b94cdba4&format=html.

Sequence analysis and alignment

The ITS dataset comprised of 56 sequences with 730 aligned nucleotide characters, of which 563 characters were constant and 113 were potentially informative sites. The Maximum Likelihood (ML) tree of the ITS data set is presented here, with Bootstrap support values being indicated on the branches. Arundinella is shown to be monophyletic with three strongly supported clades. The three accessions of A. namprikensis aggregated together (BS = 100) and are recovered within one of the three clades as sister to A. stenostachya and A. bengalensis with well support value (BS= 93). The other two morphologically allied species A. nepalensis and A. cochinchinensis are distantly related as depicted from the phylogenetic interpretation.

Maximum likelihood and Bayesian phylogeny estimates

The ingroup taxa belonging to Arundinella is recovered monophyletic (100 BP; 1 PP) in ML and Bayesian Analyses. The topologies recovered is congruent after common rooting on Miscanthus lutarioriparius Coix lacryma-jobi , Ischaemum afrum and Cymbopogon flexosus ( Fig. 4 ).

Discussion and conclusion

Arundinella namprikensis is presented here with detailed morphological description, illustration and photoplate. The novelty of the species is also supported through phylogenetic analysis based on nuclear ITS data.The molecular evidences clearly support its segregation within the genus Arundinella . A comparison based on most prominent morphological features among the close allied species, viz. A. nepalensis , A. cochinchinensis and A. stenostachya H.Peng & L.Q. Jiang (2022: 83) are also tabulated herewith ( Table 1 ). The circumscription of the new species appears sufficiently distinct from its allied species. The status of the new species is supported by morphological as well as molecular data. A key to the species of Arundinella found in Sikkim is also constructed for better taxonomic understanding.

The proposed new species, Arundinella namprikensis is a unique member of the genus Arundinella . It can be readily identified by the universal presence of bisexual lower floret. Besides, its glabrous and smooth (not scaly) rhizome and glabrous culm nodes are other features through which this taxon maintains its uniqueness sufficiently from its close relatives A. nepalensis and A. cochinchinensis as well as also from other members of the genus.

Apparent resemblance of Arundinella namprikensis has been noticed with A. stenostachya , a recently re-evaluated species, particularly in similar habit, tuberculate-hispid leaf blades, villous rachis axils, almost equal callus hairs, however, the new species can be readily distinguished from the latter one by its glabrous and smooth rhizomes (versus whitish pubescent and scaly), glabrous culm nodes (versus bearded or glabrescent), leaf sheaths ciliate along one margin only (versus both margins densely cilicate), 0.3–0.5 mm high ligule (versus 0.5-1 mm), loose and larger panicle (versus dense and shorter), mostly smooth and glabrous central axis (versus scabrid, sparsely pubescent), up to 20 cm long panicle branches (versus up to 10 cm long), 4.0–5.0 mm long spikelets (versus 2.5–3.7 mm long), 1.2-8 mm long pedicels (versus 0.3–2.2 mm long), 2.8–4 mm long lower glumes (versus 1.9–3.1 mm long), (4-)5–7-veined with keeled midvein scabrid towards apex (versus 3–5-scabrous veined), 5–7-veined upper glumes (versus strictly 5-veined), bisexual lower floret (versus staminate or barren), 3–4 mm long (versus 1.9–2.9 mm) 7-veined (versus 3–5- veined) lower lemma, 2.3–2.4 mm long upper palea (versus 1.6−2.1 mm), 1/4–1/2 length of lemma long callus hairs (versus 1/10–1/5 length of lemma), 4.5–5.0 mm long persistent awn (versus up to 2 mm, soon deciduous) and 1.0–2.0 mm long anthers (versus 0.7–1.1 mm long).

Based on culm, leaf sheath indumentum and mostly quantitative characters of spikelets, the presumed new species appears superficially similar to Arundinella intricata (1920:112). Though the significantly smaller panicle (below 20 cm long) with scabrid-hispidulous central axis and lower staminate floret of A. intricata makes noteworthy difference from Arundinella namprikensis sp. nov. where panicle is much larger (40-65 cm long) with smooth central axis (scabrid towards apex only) and lower floret is always bisexual.

Figures

FIGURE 1. A. namprikensis: A: Habit. B: Synflorescence in part (inset arrangement of spikelets). [Photo by SS]

FIGURE 2. Arundinella namprikensis: A: Habit (part). B: Ligule. C: Spikelet pair. D: Lower glume (abaxial surface). E: Upper glume (abaxial surface). F–I: Parts of lower floret: F: Lower lemma (abaxial surface). G: Lower palea (adaxial surface). H: Lodicules. I: Stamens & pistil. J: Upper floret. K–N: Parts of upper floret. K: Upper lemma (abaxial surface). L: Upper palea (adaxial surface). M: Lodicules. N: Stamens & pistil. [Drawing by SS]

FIGURE 3. A. namprikensis: A: Spikelet pair. B: Lower glume (lateral view). C: Lower glume (abaxial surface). D: Upper glume (lateral view). E: Upper glume (abaxial surface). F: Florets after removing the glumes. G: Lower floret. H–L: Parts of lower floret: H: Lower lemma (abaxial surface). I: Lower palea (abaxial surface). J: Lower palea (adaxial surface). K: Lodicules. L: Stamens & pistil. M: Upper floret. N–R: Parts of upper floret. N: Upper lemma (abaxial surface). O: Upper palea (abaxial surface). P: Upper palea (adaxial surface). Q: Lodicules. R: Stamens & pistil.

FIGURE 4. Best ML tree inferred with RaxML from ITS region (730 aligned nucleotides) for 56 accessions of 21 ingroup species plus four outgroup rooted on Miscanthus lutarioriparius Coix lacryma, Ischaemum afrum and Cymbopogon flexosus. Support values ≥ 75% BS are displayed above the branches. Bayesian Posterior probability values≥ 0.95 below or side of BP values. [Photo by MDD].