Pseudochirita trifoliata T.V.Do & F.Wen, 2021

Do, Truong Van, Hoang, Mai Thi, Xin, Zi-Bing, Wei, Yi-Gang, Meng, De-Chang & Wen, Fang, 2021, Pseudochirita trifoliata (Gesneriaceae), a new species from karst limestone in northern Vietnam, Phytotaxa 489 (2), pp. 182-190 : 183-189

Pseudochirita trifoliata T.V.Do & F.Wen , sp. nov. ( Figs. 1–3 )

The new species differs from Pseudochirita guangxiensis by having leaves in whorls of three (vs. opposite in pairs), infundibuliform calyx tube (vs. campanulate to cupuliform), staminodes number (two vs. three), glabrous ovary (vs. glandular puberulent), glabrescent to glabrous style (vs. glandular puberulent) and longer capsule (5.5–7 cm long vs. 3–4.5 cm long).

Type: — VIETNAM. Thanh Hoa province: Pu Luong Nature Reserve, Ba Thuoc district, Thanh Son commune, Kho Muong village , moist and humic limestone cliffs nearby rice field, 20°28.894’N, 105°07.902’E, elev. ca. 371 m, 26 July 2020, Do Van Truong ĐVT 371 (Holotype VNMN!, isotypes IBK!, VNMN!) .

Perennial herbs to subshrubs. Stems up to 120 cm tall, many branches appearing from base, densely velutinous. Leaves in whorls of three, strongly anisophyllous; petioles 1–8 cm long, densely appressed grey villous; leaf blade ovate to elliptic, (3–)6–22(–25) × (2.5–)4–9(–11) cm, adaxially pubescent, abaxially densely appressed grey villous; base strongly oblique, broadly cuneate to rounded; apex acute to abruptly acuminate, ca. 1 cm long; margin serrulate; lateral veins 9–11 pairs, slightly sunken on adaxial leaf surface and prominent on abaxial leaf surface. Inflorescences dichasial cymes, 1–3-branched, cyme 3–18-flowered, axillary near stem apex; peduncles/1 st hypopodium 10–13 cm long, 2 nd axis hypopodium 2–5 cm long, 3 rd axis 1–1.5 cm long, all pubescent; bracts 2, persistent, semi-orbicular, involucrate, 1–1.2 cm in diam., yellowish-green, outside with dense glandular indumentum, inside glabrous, margin entire; pedicel 3–5 mm long, sparsely spreading villous. Calyx with connate sepals, forming an infundibuliform calyx tube, 10–16 × 5–7 mm, shallowly 5-lobed, actinomorphic, lobes broadly triangular, 4–5 × 2–3 mm, pale yellow, outside densely glandular, inside glabrous, margin entire, apex acute. Corolla zygomorphic, greenish to pale yellow to yellowish-white, 3–4.5 cm long, outside sparsely glandular, inside glabrous; tube infundibuliform-tubular, 3–3.8 cm long, suddenly constricted at ca. a third of corolla tube from the base, 1.4–1.8 cm long from the bottom to a third of tube, 2–3 mm in diam. at the bottom, somewhat constricted at the mouth, 1.6–2 cm long from a third of tube to the mouth, 1.2–1.3 cm in diam. near the mouth; limb distinctly 2-lipped, adaxial lip 2-lobed, usually retroflexed, shorter than abaxial lips, lobes broadly ovate, 3–4 × 2.5–3 mm, apex rounded, abaxial lip unequally 3-lobed, central one symmetrical and narrower than the two lateral lobes, lobes broadly ovate or sub-orbicular, 5–6 × 3–4 mm, apex acute; throat with two yellow ridges on tube floor. Stamens 2, equal, included, adnate to 1.1–1.3 cm above the base of corolla tube; filaments straight, filiform, 1.3–1.5 cm long, white, with some glands at the tip close to the anthers; anthers basifixed, coherent at apex, 1.8–2 mm long, glabrous, thecae parallel, not confluent at the apex, dehiscing longitudinally, not projecting. Staminodes 2, equal, adnate to 1.3–1.5 cm above the base of corolla tube, filaments filiform, 1.2–1.4 cm long, straight, brownish, glabrous, apex capitate. Disc cupular, 2–2.2 mm high, yellow, margin entire, glabrous. Pistil linear, 2.9–3.3 cm long; stipitate, 8–10 mm long, 1–1.2 mm in diam., narrower than ovary, but somewhat wider than style, white, glabrescent to glabrous; ovary 10–11 mm long, 1.5–2 mm in diam., green, glabrous; style 9–10 mm long, 0.8–1 mm in diam., white, glabrescent to glabrous; stigma green, adaxial lobe smaller, broadly triangular, 1–1.2 mm long, apex acute; abaxial lobe larger, narrowly obtrapeziform, 1.5–2 mm long, apex emarginate. Capsule oblong, straight in relation to pedicel, 5.5–7 cm long, 2.5–3 mm in diam., glabrous.

Phenology: —Flowering occurs from May to August, and fruiting from June to September.

Etymology: —The specific epithet “ trifoliata ” is derived from the number of leaves at each node, which is the most notable morphological feature of the new species.

Vernacular name: —Cây giả Ri ta 3 lá (name translation into Vietnamese).

Distribution and habitat: — Pseudochirita trifoliata is currently known from two localities: i.e. Kho Muong cave at Pu Luong Nature Reserve, and Doi cave at Ngoc Son-Ngo Luong Nature Reserve, both in northern Vietnam, lying on the Cuc Phuong-Pu Luong limestone mountain range ( Fig. 4 ). This species grows on humid limestone rock surfaces on the ground at limestone cave entrances or on moist and humid limestone cliffs. It is usually accompanied by Adiantum sp. , Begonia sp. , Elatostema sp. , Gynostemma sp. , Henckelia sp. , Microchirita sp. , Pellionia sp. , Petrocodon sp. , Pilea sp. , Tectaria sp. , and Tradescantia sp.

Conservation status: —We currently know of five collection points of Pseudochirita trifoliata , all from the Cuc Phuong-Pu Luong limestone mountain range, northern Vietnam and together appearing to represent at least three distinct populations. One population is at the Kho Muong cave, and another is at the margins of a limestone hill nearby a rice field of the Kho Muong village, both located in Pu Luong Nature Reserve of Thanh Hoa province. A third population is located at the Doi cave in Ngoc Son commune, within the Ngoc Son-Ngo Luong Nature Reserve of Hoa Binh province. Estimated from the locations of the three populations, the Extent of Occurrence (EOO) is ca. 100 km 2 and the Area of Occupancy (AOO) is ca. 12 km 2. All three populations occur in buffer zones of the Nature Reserves. On this basis, and in accordance with the IUCN Red List criteria ( IUCN 2019), we propose to categorize this species as Near Threatened (NT). The Endangered (EN) category could be used (B2a, AOO <500 km 2 and the number of locations ≤ 5). The fact that three populations occur in protected forest areas, however, suggests that if declines and fluctuations are occurring, they are not extensive.

Morphological affinities: — Pseudochirita trifoliata is morphologically similar to P. guangxiensis ( Fig. 3 ) by sharing an obliquely elliptic to ovate leaf blade, appressed grey villous indumentum on the abaxial leaf surface, dichasial cymes, connate sepals, zygomorphic corolla, 2 fertile stamens, and other characteristics. However, it is clearly different from the latter by a combination of morphological differences on the leaves, bracts, calyx, external corolla indumentum, staminode number, pistil length, ovary indumentum, style indumentum, and capsule length. A detailed comparison of the new species with P. guangxiensis is provided in Table 1.

Additional specimens examined (paratype): — VIETNAM. Thanh Hoa province: Pu Luong Nature Reserve, Ba Thuoc district, Thanh Son commune, Kho Muong cave , 20°28.025’N, 105°08.258’E, elev. ca. 371 m, 26 July 2020, Do Van Truong ĐVT 370 ( VNMN!) ; 21 October 2016, Wen Fang et al. 546 (IBK!, VNMN!) . Hoa Binh province: Ngoc Son-Ngo Luong Nature Reserve, Tan Lac district, Ngoc Son commune, Doi cave , 30 October 2019, Wen Fang et al. 1212 (IBK!, VNMN!) .

Figures

FIGURE 1. Holotype of Pseudochirita trifoliata T.V.Do & F.Wen sp. nov. (Do Van Truong ĐVT 371 (deposited at VNMN). (Photo by Do Van Truong)

FIGURE 2. Pseudochirita trifoliata T.V.Do & F.Wen sp. nov. A–B. Habitat & habit; C. Leaves in whorls of 3 (red arrow); D. Adaxial and abaxial leaf surfaces; E. Dichasial cyme inflorescence; F. Oblique frontal view of open flower and involucrate, semi-orbicular bracts (red arrow); G. Densely glandular indumentum outside of bracts; H. Glabrous inside of bracts; I. Infundibuliform calyx; J. Two longitudinally sectioned flowers showing internal floral parts and calyx plus pistil; K. Abaxial part of a longitudinally sectioned corolla tube showing two stamens (white arrow) and two staminodes (red arrow); L. Shape and colour of a range of pistil; M. Close up of an unequally 2- lobed stigma; N. Infructescence; O. Close up of maturing oblong capsules. (All photos by Do Van Truong from the population at the type locality)

FIGURE 3. Morphological comparison between Pseudochirita trifoliata T.V.Do & F.Wen sp. nov. (t) and P. guangxiensis (S.Z.Huang) W.T.Wang (g). A. Leaf insertion on the nodes (3-whorled in P. trifoliata, and opposite in P. guangxiensis); B. Adaxial leaf surfaces; C. Abaxial leaf surfaces; D. Cymes; E. Peduncle indumentum; F. Top view of corolla and calyx; G. Lateral view of corolla and calyx; H. Front view of corolla; I. Cut opened corolla and calyx, and pistil; J. Outside surfaces of cut opened calyx; K. Inner surfaces of cut opened calyx; L. Stamens with anthers and filaments; M. Pistil and discs; N. Top view of stigmas; O. Lateral view of stigmas. (All photos by De- Chang Meng and Fang Wen from living plants of the two species)

FIGURE 4. Distribution map of Pseudochirita trifoliata in northern Vietnam (localities indicated by black dots)