Strobilanthes spathulatibracteata D.V. Hai, Z.L. Lin & Y.F. Deng, 2023

Hai, Do Van, Thuy, Nguyen Thu, Lin, Zheli & Deng, Yunfei, 2023, Strobilanthes spathulatibracteata, a new species of Acanthaceae from northern Vietnam, Phytotaxa 597 (2), pp. 184-192 : 185-189

Strobilanthes spathulatibracteata D.V. Hai, Z.L. Lin & Y.F. Deng , sp. nov.

( Figs. 1–4 )

Type: — VIETNAM. Lao Cai Province: Van Ban District, Liem Phu Commune , elev. 741 m, 21°57’29.9”N, 104°20’26.8”E, 24 March 2019, Do Van Hai, Zheli Lin, Xixi Zhang HL 322 (holotype HN [ HN000075338 !]; isotypes, HN [ HN000075339 !, HN000075340 !, HN000075341 !, HN000075342 !], IBSC!) .

Diagnosis: — The new species resembles Strobilanthes tonkinensis Lindau (1897: 651) in the solitary terminal spicate inflorescence, but differs in hirsute (vs. pubescent) stem when young, 8–11 pairs (vs. 4–7 pairs) of secondary veins, longer (3–5 cm vs. ca. 2 cm) and hirsute (vs. pubescent) petiole, spathulate (vs. linear-spathulate) bract, spathulate (vs. linear) bracteoles, gland-tipped hirsute (vs. sparsely pubescent and gland-tipped pubescent) bracts, bracteoles and calyx, and 2-lipped (vs. equally 5-lobed) calyx. A detailed comparison between the two species is given in Table 1 .

Perennial undershrubs, up to 2 m high. Stems erect, quadrangular, sulcate, hirsute when young and glabrescent when old, internodes swollen. Leaves opposite, equal or subequal in each pair; petioles 3–5 cm long, hirsute; blades elliptic to ovate, 5–20 × 3–10 cm, adaxially hirsute when young subglabrescent, densely covered with linear cystoliths, abaxially pubescent, hirsute along the veins and secondary veins, apex acute, base cuneate to attenuate and decurrent onto the petioles, margin serrate and ciliate, lateral veins 8–11 pairs. Inflorescence of terminal spikes, 4–8 cm long, 8–14-flowered; peduncle 5–7 mm long, rachis hirsute, internodes 5–6 mm long; flowers in opposite pairs. Bracts pale green except the violet tip, persistent, 23–25 × 2–5 mm, spathulate, pinnately veined, apex truncate or rounded and retuse, margin long-ciliate with gland-tipped hairs, both surfaces subglabrous and covered with linear cystoliths; bracteoles 2, spathulate, ca. 2 × 0.2 cm, apex truncate or rounded, sometimes retuse, margin long-ciliate with gland-tipped hairs, both surfaces subglabrous and covered with linear cystoliths. Calyx ca. 2 cm long, 2-lipped, lower lip 2- lobed to 1/3 length, upper lip equally 3-lobed to 1/3 length; lobes oblong, ca. 1.5 mm broad, green except the violet tips, apex truncate or rounded, margin long-ciliate with gland-tipped hairs; both surfaces subglabrous, the exterior covered with linear cystoliths. Corolla white with purple stripes on throat and lobes, 3.5–4.5 cm long, subventricose, outside puberulent, inside hirsute; tube basally cylindrical and ca. 3 mm broad for ca. 1.5 cm then gradually widened to ca. 1 cm at the mouth; lobes 6–7 × ca. 5 mm, apex rounded. Stamens 4, included, didynamous; filaments monadelphous by a membranous sheath at base, hirsute basally, the shorter pairs 3–3.5 mm long, the longer pairs 7–8 mm long; anthers ca. 3 mm long, oblong, attached at lower 1/3. Pollen grains prolate, 3-colporate, pseudocolpi 12, with 15 longitudinal ribs, exine ornamentation reticulate. Ovary narrowly obovoid, 2.5–2.8 mm long, ca. 1.5 mm in diam., densely covered with glandular hairs; style 2.5 cm long, linear, sparsely glandular-pilose, especially at tip; stigma unequally 2-clefted. Capsule narrowly oblong-obovoid, 15–16 × 4–5 mm, apically pubescent, 4-seeded. Seeds ovate to suborbicular in outline, 4–4.5 × ca. 4 mm, pubescent with appressed mucilaginous hairs, areole small.

Etymology:— The specific epithet is derived from the Latin “ spathulatus ” and “ bracteatus ”, referring to the shape of the bracts of the new species.

Phenology:— Flowering from October to March; fruiting from November to April.

Distribution and ecology: — Strobilanthes spathulatibracteata was found from a few locations in northern Vietnam, and is probably endemic there. It grows under the shade of secondary rain forest on soils or in between soils and limestone, at elevations of 700–800 m asl. The new species is association with Leptochilus wrightii (Hooker ex Baker 1864: 160) X. C. Zhang (2012: 656) , Pteridrys australis Ching (1934: 142) , Tectaria subtriphylla ( Hooker & Arnott 1838: 256) Copeland (1907: 410) (Polypodiaceae) , Dennstaedtia zeylanica ( Swartz 1801: 91) Zink ex Fraser-Jenkins & Kandel (2015: 161) (Dennstaedtiaceae) , Rhaphidophora crassicaulis Engler & K. Krause (1908: 52) (Araceae) , Musa sp. (Musaceae) , Lanxangia tsao-ko ( Crevost & Lemarié 1917: 300) M.F. Newman & Škorničk. (2018: 24) (Zingiberaceae) , etc.

Additional specimens examined (paratypes):— VIETNAM. Bac Kan Province, Na Ri District, Kim Hy Commune , 25 March 2014, Do Van Hai et al., DVH 25032014 ( HN) ; ibid., 10 February 2023, Do Van Hai et al., VAST09- 399B ( HN) ; Lao Cai Province: Van Ban District, Liem Phu commune, elev. 802 m, 21°57’30.2”N, 104°20’22.6”E, 17 April 2011, Do Van Hai et al., DVH17042011 ( HN) ; ibid., elev. 791 m, 21°57’40.5”N, 104°20’11.9”E, 19 April 2011, Do Van Hai et al., DVH19042011 ( HN) ; Tuyen Quang Province: Ham Yen District, Cham Chu Nature Reserve , 2 October 2003, Vu Xuan Phuong et al., Phuong 6674 ( HN) ; Na Hang District, Thanh Tuong Commune, Ban Bung village , 9 December 1997, Nguyen Kim Dao 1018 ( HN) .

Conservation status:— This new species has been collected several times from the cited locations in Bac Kan, Lao Cai, Tuyen Quang provinces in northern Vietnam, but during our fieldwork in this area, we observed only one population growing on soils mixed with limestone in secondary rain forests. All places where S. spathulatibracteata grows, fall within the protected areas like nature reserves or forestry companies. Therefore, we suggest a status of Least Concern (LC) according to the IUCN Red List categories ( IUCN 2022) and criteria.

Taxonomic note: In the genus Strobilanthe s, the term “two-lipped calyx” has been used to describe species having the five calyx lobes form two groups, one with two and another with three. This character was used by Nees (1847) and Bremekamp (1944) to separate seven genera from Strobilanthes s. l., but appears to be of almost random occurrence within the genus and is of relatively little systematic importance except at the level of species ( Wood & Scotland 2003). In Vietnam, some species, e.g., Strobilanthes adpressa J.R.I. Wood (2003: 110) , S. cystolithigera Lindau (1897: 651) and S. longzhouensis H. S. Lo & D. Fang (1997: 34) , have a two-lipped calyx, but the new species can be easily distinguished from these by its spathulate bracts and bracteoles, of which the margin is long-ciliate and with gland-tipped hairs. The stamens are hirsute except the apex and the style is sparsely glandular pilose near the base but densely pilose apically.

Figures

FIGURE 1. Strobilanthes spathulatibracteata. A. Flowering branch, B. Close up of abaxial leaf blade surface, C. Abaxial surface of bract, D. Adaxial surface of bract, E. Bracteoles and calyx, F. Bracteoles, G. Calyx, H. Corolla (open), I. Stamens, J. Stamen (lateral view), K. Pistil, L. Fruit, M. Fruit (open), N. Seed (Drawn by Mrs. Le Kim Chi).

FIGURE 2. Strobilanthes spathulatibracteata. A. Habitat, B. Habit, C. Flowering branches (Photos: A by Zheli Lin; B, C by Do Van Hai).

FIGURE 3. Strobilanthes spathulatibracteata. A. Flowering branches, B. Inflorescence, C. Flower with calyx, bract and bracteoles, D. Bract and two bracteoles, E. Calyx (open), F. Corolla in front view, G. Corolla, lateral view, H. Corolla (open) to show stamens, I. Stamens, J. Anthers (lateral view), K. Pistil, L. Stigma with part of style, M. Fruit, N. Seed (Photos: A, G, L, M, N by Zheli Lin; B, C–F, H–K by Do Van Hai).

FIGURE 4. Pollen morphology of Strobilanthes spathulatibracteata. A. Pollen grain, B. Ornamentation of the pollen grain.