Wenchengia wui Bo Li, S. C. Xu & C. L. Xiang, 2025

Xu, Si-Cheng, Xiao, Jin-Fei, Xiang, Chun-Lei & Li, Bo, 2025, Unveiling the hidden diversity: the second species of Wenchengia (Lamiaceae) discovered from a dry mountaintop meadow of Hainan Island, China, PhytoKeys 259, pp. 239-247 : 239-247

Wenchengia wui Bo Li, S. C. Xu & C. L. Xiang sp. nov.

Figs 1 , 2 , 3 a – e

Diagnosis.

This species differs from W. alternifolia by its opposite phyllotaxy (vs. alternate), leaves blade oblong-ovate with round to slightly truncate bases (vs. oblanceolate to lanceolate with cuneate-decurrent bases), calyces shallowly funnelform with spreading lips (vs. funnelform with straight lips), upper lip of calyx intermediately 3 - lobed and the lobes ovate with acuminate apices (vs. shallowly 3 - toothed and the teeth acutely deltoid), lower lip of calyx trapeziform with obliquely deltoid lobes and acute apices (vs. rectangular with rounded lobes and small tines), and nutlets longitudinally 8 - ribbed (vs. 5 - ribbed).

Type.

China • Hainan Province, Sanya City, Tianya District, Baishiling Mountain , in dry mountaintop meadows, alt. 680–740 m, 30 October 2023, LB 1118 (holotype: HITBC, isotypes: CSH, IBSC, HIYBC, KUN, PE) .

Description.

Subshrubs, 15–30 cm tall, bare at base and leafy above; young stems and the petioles, lower leaf surface, and margins of young leaves purple and hirtellous. Stems woody, flexible, prostrate or ascending, branched near base, bending into inflorescences. Leaves opposite; lamina chartaceous, oblong-ovate, 2.0– 7.5 cm long, 2.0– 2.7 cm wide, apex obtuse, base round or slightly truncate, margin shallowly crenate-serrate; adaxially dark green, abaxially greenish-white, primary vein convex below and slightly concave above, lateral veins 4–6 pairs; petioles 1.0–2.0 cm long. Inflorescence raceme-like, 7.0– 17.5 cm long, solitary, terminal, flowers spirally arranged in bud, subsequently twisting and facing the same direction during anthesis; bracts purple, linear-lanceolate, 3.5–7.5 mm long, hirtellous; bracteoles caducous. Calyx green to purple, shallowly funnelform, 6.0–8.0 mm long, hirtellous outside, conspicuously veined; 2 - lipped, lips spreading; upper lip intermediately 3 - lobed, lobes equal, ovate, ca. 3.0 mm long, apex acuminate; lower lip trapeziform, 2 - lobed, lobes dilated and coalescent, obliquely deltoid, ca. 6.0 mm long, apex acute. Corolla pink, tubular-campanulate, 2.8–3.7 cm long, gradually dilated into a broad throat; tube straight, 2.3–2.7 cm long, sparsely puberulent outside, bearded at lower middle inside; 2 - lipped; upper lip 2 - lobed, lobes subequal, ± round, 5.0–6.0 mm wide; lower lip 3 - lobed, middle lobe largest, subelliptic, ca. 1 cm wide, finely crenate at margin. Stamens 4, posterior pair longer, slightly exserted from corolla tube; filaments arcuate, with capitate glandular hairs; anthers ovoid, glabrous, 2 - celled, thecae divaricate. Style longer than stamens, unequally 2 - clefted at apex, lobes subulate. Ovary terete, shallowly lobed, puberulent and glandular at apex, disc poorly developed. Nutlets 4, broadly obovoid, ca. 1.5 mm long, ca. 1.5 mm wide, connected to the receptacle by slender stalks; apically tuberculate and pubescent, longitudinally 8 - ribbed, areole ca. 0.30 times as long as the nutlet.

Phenology.

Flowering from July to October and fruiting from August to December.

Etymology.

The specific epithet “ Wui ” is dedicated to Chengyi Wu for his tremendous contributions to the taxonomy of Lamiaceae in China, who also described and named the genus Wenchengia in honor of his teacher Wencheng Wu.

Vernacular name.

Simplified Chinese: 吴氏韫珍花; Chinese pinyin: wú shì yùn zhēn huā.

Distribution and habitat.

Currently, W. wui is only known from its type locality in Tianya District, Sanya City, in southern Hainan Province, China. It inhabits a dry mountaintop meadow, at an altitude of 680–740 m (Figs 1 A , 3 a ). The place is surrounded by lowland rainforest and has a distinctive microclimate. It contains large, exposed rocks with sparse soil, where precipitation is abundant but poorly retained. The vegetation is predominantly ferns and interspersed with low herbs and shrubs.

Provisional conservation status.

Wenchengia wui is currently known only from the mountaintop meadows of its type locality, where it occupies a small and ecologically specialized habitat totaling less than 1 km 2. Our field observations in October 2023 recorded fewer than 300 individuals in the extant population. Crucially, the type locality is an outdoor tourism hotspot of Sanya City, with large crowds of tourists gathering there for hiking, camping, or picnicking, causing severe disturbance and damage to the local habitat (personal observation by the authors). The site has not yet been included within any protected area, and stringent protective measures are urgently needed. Consequently, we categorize W. wui as Critically Endangered (CR) under criteria B [B 2 a, b (ii, iii)] of the IUCN Red List Categories ( IUCN 2012), for its highly restricted area of occurrence and the likely decline in both its extent and habitat quality. Precise geographic location is therefore not disclosed in the type information to prevent vandalism.

Taxonomic notes.

The two species of Wenchengia can be distinguished from each other by their phyllotaxy, leaves, calyces, and nutlets. Firstly, W. wui has opposite phyllotaxy (Figs 1 E , 3 b ) whereas W. alternifolia has alternate phyllotaxy (Fig. 3 B ); the leaves of W. wui are oblong-ovate with round to slightly truncate bases (Figs 1 D , 3 c ), in contrast to the oblanceolate to lanceolate leaves with cuneate-decurrent bases in W. alternifolia (Fig. 3 C ). Secondly, in W. wui , the calyces are shallowly funnelform with spreading lips (Figs 1 K , 3 e ), the upper lip intermediately 3 - lobed with lobes ovate and apically acuminate, while the lower lip trapeziform with lobes obliquely deltoid and apically acute (Figs 1 M , 3 d ). In contrast, W. alternifolia has funnelform calyces with straight lips (Fig. 3 E ), the upper lip shallowly 3 - toothed with teeth acutely deltoid, the lower lip rectangular with rounded lobes and very small tines (Fig. 3 D ). Thirdly, nutlets of W. wui are longitudinally 8 - ribbed (Fig. 1 O, P ) but those of W. alternifolia are 5 - ribbed. In addition, nutlets of W. wui have fragile stalks and easily detach after maturation (author’s personal observation), unlike those of W. alternifolia , which hang outside the calyx through a crack of the calyx tube ( Li et al. 2014). Furthermore, the two species differ remarkably in their habitat. W. wui grows in dry, open mountaintop meadows (Fig. 1 A , 3 a ), while W. alternifolia inhabits shaded, moist environment within dense rainforests (Fig. 3 A ).

Additional specimens examined.

Wenchengia alternifolia : China • Hainan Province, Baoting County, Xinglong Town, Shuangximu Valley , 20 September 1935, F. C. How 73689 ( HUHA 00002271 !, IBK 00342109 !, SN 004110 !) ; Hainan Province, Wanning County, Nanlin Farm , 18°43'27.45"N, 110°04'51.00"E, alt. 137 m, 22 May 2018, ZXX 18078 ( KUN 1437648 !) . Vietnam • Da Nang Province, Ba Na Hills, Mt Bani, about 25 km from Tourane , 4–13 June 1927, 3376 ( P 03006424 !) ; in the same location, July 1927, 3882 ( P 04442939 !) ; Thua Thien Province, Hai-Mit , 1516 ( P 03006423 !, P 03006423 !) .

Figures

Figure 1. Wenchengia wui sp. nov. A. Habitat; B. Habit; C. Rootstock; D. Leaves; E. Leafy stem, showing its opposite phyllotaxy; F. Inflorescences; G, H. Flowers; I. Lateral and dorsal views of corolla; J. Top view of corolla; K. Top view of calyces; L. Dissected corolla; M. Dissected calyx; N. Lateral view of ovary and pedicel; O, P. Nutlets connected by stalks.

Figure 2. Wenchengia wui sp. nov. A. Branch with leaves and inflorescence; B. Flower (lateral view); C. Calyx (top and dorsal views); D. Dissected calyx; E. Dissected corolla, showing stamens; F. Ovary and style; G. Nutlets connected by stalks (dorsal and ventral views).

Figure 3. Comparison of habitats and morphology between Wenchengia alternifolia (A – E) and W. wui sp. nov (a – e). A, a. Habitat; B, b. Phyllotaxy; C, c. Leaves (adaxial and abaxial views); D, d. Dissected calyx; E, e. General morphology of calyces.