Spiradiclis liboensis L. Wu & W. J. Liu, 2022

Song, Xiao-Fei, Liu, Wen-Jian, Chen, Ao-Xue, Yao, Zheng-Ming, Lan, Hong-Bo & Wu, Lei, 2022, Spiradiclis liboensis (Rubiaceae), a new species from limestone mountain areas in Guizhou, China, PhytoKeys 204, pp. 73-81 : 73

Spiradiclis liboensis L. Wu & W. J. Liu sp. nov.

Figs 1 , 2

Type.

China. Guizhou Province: Libo County, Maolan National Nature Reserve , 107°56'E, 22°5'N, alt. 900 m, 9 May 2018 (flower), L. Wu & F. L. Chen 6410 (holotype: CSFI barcode 069626, isotypes: CSFI, IBK) .

Diagnosis.

The new species is similar to S. guangdongensis and S. jingxiensis , but differs from the former by the triangular (vs. linear), ca. 0.8 (vs. 1-3.5) mm long stipule, 1.6-2.2 (vs. 0.8-1) cm long corolla tube and stigma and anthers positioned at (vs. exserted 5 mm above) the throat of the corolla tube in the long-styled form and short-styled form, respectively, and from the latter by its green (vs. purple) stem, 0.8-2.2 mm (vs. 3-5 mm) long pedicels, white (vs. pink) corolla with tube ca. 1.2 mm wide at the lower part, enlarged at the upper part and ca. 4.8 mm wide at the throat (vs. ca. 2 mm).

Description.

Perennial herbs, creeping, rooting at most nodes; stems terete, slender, densely pubescent, internodes 1-5 mm long. Petiole 2-9 mm long, sparsely pubescent; leaf blades papery when dry, adaxially green to dark green, abaxially lightly green, ovate to orbicular, 0.3-1.4 × 0.3-1.2 cm, base truncate to rounded, apex subacute to obtuse, adaxially sparsely hispidulous, abaxially pubescent along veins; secondary veins 3-4 on each side; stipules triangular, ca. 0.8 mm long, pubescent, usually deciduous. Inflorescence terminal, cymose, with 1-2 flowers; peduncle 0-0.5 mm long; bracteoles linear or narrowly triangular, 1-2.3 mm long, puberulent. Flowers distylous, 5-merous; pedicels pubescent, 0.8-2.2 mm long. Calyx pubescent; hypanthium obconical, 1.3-1.6 mm long; lobes linear, 1.3-1.8 mm long, outside puberulent. Corolla white, salverform, puberulent outside; tube 1.6-2.2 cm long, ca. 1.2 mm wide at the lower part, enlarged at the upper part, ca. 4.8 mm wide at the throat; lobes subovate, 6-9 × 3-6 mm, puberulent inside; stamens 5; anthers linear-oblong, 1.4-1.6 mm long; stigma bilobed; ovary 2-celled. Long-styled flowers: corolla tube inside with a villous ring below throat and densely pubescent from the throat to the base of the corolla lobes; stamens inserted at the middle of the corolla tube; filaments ca. 0.4 mm long; stigmas positioned at the throat of the corolla tube; lobes elliptic, ca. 1.7 mm long; styles 1.5-1.8 cm long, glabrous. Short-styled flowers: corolla tube pubescent inside; stamens positioned at the throat of the corolla tube; filaments ca. 1.5 mm long; stigmas inserted slightly above the middle of the corolla tube; stigma lobes lanceolate, ca. 3 mm long; styles 7-9 mm long, glabrous. Capsules subglobose, ca. 2.5 mm in diam., pubescent, untwisted valves when mature.

Distribution and habitat.

Spiradiclis liboensis is currently only known from limestone hills in the Maolan National Nature Reserve, Libo County, Guizhou Province, south-western China. It grows on humid slopes or within crevices under the evergreen broad-leaved forest, at an altitude of 850-950 m. The forest here is dominated by trees of Fagaceae (e.g. Cyclobalanopsis glauca (Thunb.) Oerst.), Lauraceae (e.g. Phoebe calcarea S. K. Lee et F. N. Wei and Lindera megaphylla Hemsl.) and Sapindaceae (e.g. Handeliodendron bodinieri (H. Lév.) Rehder).

Phenology.

Flowering from May to June, fruiting from June to October.

Etymology.

The specific epithet is derived from the type locality, Libo County, southern China. The Chinese name is given as “荔波螺序草” ( lì bō luó xù cǎo).

Additional specimens examined

(paratypes). China. Guizhou Province: Libo County, the type locality, 9 May 2019 (fruit), F. C. Chen & Z. B. Xiong CFL5029 (IBSC!), 14 October 2019, F. L. Chen 19101401 (CSFI!, IBSC!) .

Provisional conservation status.

After a series of investigations into limestone areas of Guizhou Province, five populations of the new species with approximately 60 individuals at each site have been observed. All the individuals are distributed in Maolan National Nature Reserve and the habitats are mostly in good condition, except for the population adjacent to a tourism road. Hence, according to the IUCN Standards and Petitions Subcommittee (2019) Guidelines, this species is currently evaluated as ‘Vulnerable’ [VU].

Discussion.

Spiradiclis liboensis is morphologically very similar to S. guangdongensis and S. jingxiensis . According to the classification of Lo (1999), the three species belong to the subgenus Spiradiclis Sinospiradiclis . However, the new species differs from S. guangdongensis H. S. Lo mainly by its triangular, shorter stipule, much longer corolla tube and stigma and anthers positioned at the throat of the corolla tube in the long-styled form and short-styled form, respectively, and from S. jingxiensis R. J. Wang mainly by its green stem, shorter pedicels, white corolla with tube ca. 1.2 mm wide at the lower part, enlarged at the upper part, ca. 4.8 mm wide at the throat. The detailed morphological comparisons amongst them are listed in Table 1 .

Currently, there are nine other species of Spiradiclis with creeping or decumbent habits and small leaf blades shorter than 3 cm, viz., S. danxiashanensis R. J. Wang, S. glandulosa L. Wu & Q. R. Liu, S. hainanensis , S. lui Liu Yan & L. Wu, S. karstana L. Wu, X. Li & Q. R. Liu, S. pauciflora L. Wu & Q.R. Liu, S. tubiflora L. Wu, B. M. Wang & B. Pan, S. pengshuiensis B. Pan & R. J. Wang and S. umbelliformis H. S. Lo ( Chen and Taylor 2011; Wang et al. 2015; Wu et al. 2015a, b, 2019b; Zhang et al. 2018). To better differentiate these species, a key is provided.

Figures

Figure 1. Spiradiclis liboensis L. Wu & W. J. Liu. A habit B leaf blade, adaxial and abaxial views C short-styled flower D long-styled flower E infructescence F calyx and disc in face view G stipules. Drawn by X. Y. Zeng.

Figure 2. Spiradiclis liboensis L. Wu & W. J. Liu. A habitat (the arrow shows the place of growth) B habit C leaves showing variation range D inflorescence, side view E-F dissected short-styled flower and long-styled flower showing floral parts G long-styled flower, frontal view H young capsules I discs in face view. S. jingxiensis J habit. (Designed by Lei Wu and Xiao-Fei Song).