Spiradiclis hechiensis C.Xiong & L.Wu, 2025

Xiong, Chi, Sun, Fu-Zhang, Yang, Yu-Xin & Wu, Lei, 2025, Spiradiclis hechiensis (Rubiaceae), a new cave-dwelling species from Northwest Guangxi, China, Phytotaxa 689 (2), pp. 262-268 : 263-265

Spiradiclis hechiensis C.Xiong & L.Wu , sp. nov. ( Figs. 1 & 2A–K )

Diagnosis: — Spiradiclis hechiensis resembles S. pauciflora ( Figs. 2 L–O ) in floral characteristics, including the shape and color of the corolla. It is easily distinguished from the latter by its obovate to rhombic-elliptic leaf blade, 4–7 secondary veins, linear bracts, 1–4- flowered inflorescence, ellipsoid capsules, 1.2–2.2 mm in diam., and 0.4–0.6 mm long seed.

Type: — CHINA. Guangxi Zhuangzu Autonomous Region: Hechi City, Celing Town, Laba Village, 24°52′N, 107°44′E, elev. ca. 550 m, 19 September 2023, Chi Xiong et al. XC20230919-02 (holotype IBK!, isotypes IBK!, CSFI!)

Description: —Perennial herbs, up to 15 cm tall. Stems densely white villous, lower part procumbent, rooting at nodes, upper part ascending. Petiole 0–5 mm long, villous; leaf blade drying thin papery, obovate to rhombic-elliptic, 0.8–3.6 × 0.4–1.6 cm, base attenuate to narrowly cuneate, apex obtuse to acute, adaxially green, abaxially pale green or sometimes purplish red, both surfaces densely pubescent, margin entire, ciliate; secondary veins 4–7 on each side; stipules broad triangular, ca. 1 mm long, 0.5 mm wide, pubescent. Inflorescence cymose, generally 1–4-flowered, sometimes up to 6-flowered; peduncles 0.8–3.2 cm long, villous; bracts linear, 3–5 mm long, villous; pedicels 0.5–4 mm long, villous. Calyx 5-lobed, hypanthium obconical, 1.2–1.5 mm long, densely villous; lobes equal, linear lanceolate, 1.6–1.8 × 0.2–0.4 mm, sparsely villous. Corolla white, funnelform, constricted at the throat, sparsely villous along the longitudinally ridge on the outside, densely yellow villous inside the throat, and lobes glandular-pubescent; tube 6–8 mm long, slightly enlarged at the base; lobes triangular-ovate, 2–2.5 × ca. 2 mm. Stamens 5, inserted near the base of tube, filaments 1–1.5 mm long, anthers dorsifixed, linear, ca. 1 mm long. Ovary 2-celled, style 4.5–5 mm long, stigma bilobed, lobes elliptic, 0.5–0.8 mm, appearing near the throat of corolla tube. Capsules ellipsoid, 1.2–2.2 mm in diam., ca. 3 mm long, densely villous, valves 4, slightly twisted when mature. Seed numerous, 0.4–0.6 mm long, brownish yellow to dark brown, irregular pyramid to cuboid, foveolate on surface.

Distribution and Ecology: —This new species is currently found only at the type locality at an elevation of ca. 550 m. This species grows on rocks at the entrance zone of a karst cave.

Phenology: —Flowering from July to September; fruiting from August to December.

Etymology: —The specific epithet ‘ hechiensis ’ refers to the type locality where the new species was found, Hechi City, Northwest Guangxi. The Chinese name is “hé chí luó xù cǎo (OiṀṞ"ḍ)”.

Provisional conservation status: — Spiradiclis hechiensis is currently known to exist only in one population at the type locality. The population size is estimated to be around 50–100 mature individuals. The extent of occurrence (EOO) and the area of occupancy (AOO) of the new species are about 150 m 2 and 25 m 2. This species grows at the entrance zone of a cave located on the mountainside. At the foot of the mountain, there is a farmed citrus orchard. A trail connects the citrus grove to the cave entrance, indicating clear signs of human activity. Following the IUCN (The International Union for Conservation of Nature and Natural Resources) guidelines ( IUCN, 2024), the species is temporarily assessed as Critically Endangered [CR B1+2ab (iii)].

Discussion: — Spiradiclis hechiensis morphologically resembles S. pauciflora in having creeping to ascending stems and a white, funnel-shaped corolla. It can be easily distinguished from the latter by several characteristics, including the shape of leaf blades, bracts, and calyx lobes, the number of secondary veins and flowers, and the size of capsules and seeds. The detailed characteristics of the related species are provided in Table 1.

Approximately 94% of the Spiradiclis species in China are identified as distylous plants, with over 30 species exhibiting both long- and short-styled flowers within the same population ( Wu et al. 2019b). Distylous plants possess two distinct flower types, where the arrangement of the pistil and stamens is complementary, facilitating crosspollination ( Sampson & Krebs 2012). This mechanism can promote mating between different flower types and reduce inbreeding ( Carlson et al. 2008).

In our field survey, we found that all individuals of the new species we studied were of the long-styled form. This observation can be interpreted in two ways: 1) The population may contain both flower types, but the short-styled individuals could be too few to be detected during our study. 2) The flowers in this population might be monostylous, with all individuals being long-styled, a phenomenon that is rarely documented in Spiradiclis , such as S. reticulata L. Wu, Q. Yuan & J. L. Li ( Li et al. 2021) . Consequently, further research on this species is essential to enhance our understanding of its reproductive and pollination mechanisms.

Figures

FIGURE 1. Holotype of Spiradiclis hechiensis (IBK00458114), photographed by Zhu-Fang Bin.

FIGURE 2. Spiradiclis hechiensis.—A. Habitat (the arrow shows the place of growth).—B, D. Habit.—C. Leaves showing variation range.—E. Front view, side view and anatomy of flower.—F. Stipule.—G. Infructescence in side view.—H. Dehiscent capsules.—I. Transverse section of a young capsule.—J. Seeds.—K. SEM micrographs of seeds. S. pauciflora.—L & M. Habit.—N.Short-styled flower opened to show floral parts.—O. Long-styled flower opened to show floral parts. (K photographed by Yu-Jing Wei, L–O by Lei Wu, and others by Chi Xiong)