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Research Article
Spiradiclis detianensis (Rubiaceae, Ophiorrhizeae), a new species from southwestern Guangxi, China
expand article infoZhao-Jie Wen§, Yun-Fen Huang|, Yan-Hua Hu§, Khang Sinh Nguyen, Lei Wu§
‡ Jiangxi Academy of Forestry, Nanchang, China
§ Central South University of Forestry and Technology, Changsha, China
| Guangxi Institute of Traditional Medical & Pharmaceutical Sciences, Nanning, China
¶ Institute of Ecology and Biological Resources, Vietnam Academy of Science and Technology, Hanoi, Vietnam
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Abstract

A new species of Rubiaceae, Spiradiclis detianensis is described from a limestone karst area of southwestern China. This new species is morphologically similar to S. cordata and S. spathulata. All of them have rosetted habit and long peduncles, but it differs from the former by the cuneate leaf bases (vs. basally cordate) and much longer corolla tubes (1.8–2.2 cm long vs. ca. 5 mm long), and from the latter mainly by its tubular-funnel shaped corolla (vs. slenderly salver shaped), 4.5–6.8 (vs. 1.5–2) mm in diam, inside throat and corolla densely puberulent (vs. glabrous except a ring of long hairs at the middle). It also resembles to S. tubiflora, but differs clearly by its subrosulate habit (vs. procumbent to creeping), longer leaf blades (7.0–10.5 cm vs. 0.5–2.5 cm) and longer corolla tubes (18–22 mm vs. 14–16 mm). At same time, color photos, illustrations, detailed descriptions and conservation status of the new species are provided.

Keywords

China, Guangxi, limestone, Rubiaceae, taxonomy

Introduction

Spiradiclis Blume is a morphological complex genus of Ophiorrhizeae (Rubiaceae). It is usually distinguished from its relatives by the subglobose or linear-oblong capsules with two or four twisted or straight valves when matured (Lo et al. 1983; Robbrecht 1988; Deb and Rout 1989; Lo 1999; Chen and Taylor 2011). In spite of the characteristic capsule form, the monophyly of the genus has been queried based on recent molecular evidence (Rydin et al. 2009; Razafimandimbison and Rydin 2019). Razafimandimbison and Rydin (2019) even reduced Spiradiclis and Keenania Hook.f. to the synonymy of Ophiorrhiza L. However, we find that the relationship between Spiradiclis and its relatives needs further research and thus we prefer to accept the traditional concept of Spiradiclis here, for the unique capsule form of the genus.

There are approximate 58 species of Spiradiclis, distributed in southeastern Asia and concentrated in southwestern China and northeastern India (Chen and Taylor 2011; Deng et al. 2014; Wang et al. 2015; Wen et al. 2015; Wu et al. 2015a, 2015b, 2016, 2019a, 2019b; Wang 2016a, 2016b; Pan et al. 2016, 2019; Liu et al. 2018; Zhang et al. 2018; Wen et al. 2019; Li et al. 2021). In China, 52 known species of Spiradiclis are recorded (Li et al. 2021).

Most representatives have a narrow habitat and prefer to grow at wet places on hill slopes or entrances of caves in limestone areas. During a field investigation to the neighboring regions between China and Vietnam in 2013, the second author came across a peculiar population of Rubiaceae. According to its calciphile habitat and rosetted habit, it is easy to associate with Spiradiclis. However, the flower shape of this population is very different from that of the known species of the genus. Its corollas are tubular-funnel shaped, with 1.8–2.2 cm long tubes, sharply shrunken near base, 4.5–6.8 mm in diam. at throat and 1.8–2.5 mm in diam. near the base, while the corollas of the genus are usually very short or slender. Hence, we revisited this population and collected its capsules. Their subglobose shape and dehiscence with 4 valves clearly indicate this population represents a species of the genus Spiradiclis. After careful comparisons with relevant literatures and examining specimens in herbaria, we found that our plant is most similar to S. cordata H.S. Lo & W.L. Sha and S. spathulata X.X. Chen & C.C. Huang, two species of subgenusSinospiradiclis, but it can be distinguished from the former by the cuneate leaf bases and much longer corolla tubes, and from the latter by its tubular-funnel shaped corolla and without a villous ring inside corolla. We conclude that this population represents an undescribed species and formally treat it here.

Material and methods

Materials are deposited at the herbarium of Forest Plants in Central South University of Forestry and Technology (CSFI) and Guangxi Institute of Botany, Guangxi Zhuang Autonomous Region and Chinese Academy of Sciences (IBK) – herbarium acronyms follow Thiers (continuously updated). Morphological observations and measurements of the new species are based on living material in the field and dry specimens.

Taxonomic treatment

Spiradiclis detianensis L.Wu, Y.F.Huang & Z.J.Wen, sp. nov.

Figs 1, 2 A – I

Type

China. Guangxi: Daxin county, Shuolong town, Detian village, 22°52'N, 106°43'E, elevation 650–750 m, 30 March 2018 (fl.), Zhao-Jie Wen & Guang-Fu Mou 18033001 (holotype: CSFI [CSFI069613]; isotypes: CSFI, IBK).

Diagnosis

The new species is similar to Spiradiclis cordata and S. tubiflora, but it differs from the former mainly by the cuneate leaf base (vs. cordate) and much longer corolla tubes (1.8–2.2 cm long vs. ca. 5 mm long), and from the latter by its subrosulate habit (vs. procumbent to creeping), longer and wider leaf blades (7.0–10.5 × 2.0–3.5 cm vs. 0.5–2.5 × 0.4–1.5 cm), more secondary veins (7–10 pairs vs. 3–5 pairs) and longer corolla tubes (18–22 mm vs. 14–16 mm).

Description

Perennial herb, up to 15 cm tall; stems densely pubescent, erect or ascending, lower part rooting at nodes. Leaves subrosulate; petiole 0.8–1.7 cm long; leaf blade drying papery, obovate-lanceolate or oblong, 7.0–10.5 × 2.0–3.5 cm, obtuse or acute at apex, cuneate at base, adaxially dark green, puberulent, abaxially light green, pubescent, densely pubescent along veins at lower surface; secondary veins in 7–10 pairs; stipules persistent, pubescent, narrowly triangular, 3.2–5.7 mm long, or 2–5-lobed, lobes linear-triangular, upper part filiform. Inflorescence cymose, 2–7-flowered; peduncle 9–14 cm long, pubescent; bracts linear-triangular, 4–6 mm long, subglabrous; pedicels 0.5–5 mm long, pubescent. Flowers distylous. Calyx puberulent; hypanthium portion obconic, ca. 2 mm long; lobes triangular, 1.2–2.9 mm long, acute at apex. Corolla white to pink, tubular-funnel shaped, puberulent outside; tube 1.8–2.2 cm long, sharply enlarged at the 1/3 lower part of the corolla tube, 4.5–6.8 mm in diam. at throat, 1.8–2.5 mm in diam. near base; lobes triangular-ovate, 4.5–5.6 × 3.5–4.3 mm long. Stamens 5; anthers linear. Stigma bilobed; ovary 2-celled. Long-styled flowers: corolla tube inside with densely pubescence near base and densely puberulent above anther and on to lobes; anthers inserted near base of corolla tube, 1.9–2.3 mm long; style 1.2–1.4 cm long, puberulent; stigma inserted at between middle and throat of corolla tube, 2-lobed, lobes elliptic, 1.8–2.2 mm long. Short-styled flowers: corolla tube inside densely puberulent; anthers inserted often at or a little above middle of corolla tube, 2.6–3.3 mm long; style 1.5–3.4 mm long, glabrous; stigma near base of corolla tube, lobes ovate-triangular, 1.3–1.6 mm long. Capsules subglobose, 2.5–3.2 mm in diam., valves 4 when matured. Seeds many, angular.

Phenology

. Flowering March to April, fruiting from May to July.

Etymology

The specific epithet refers to the type locality, where a famous attraction, Detian Waterfall, is situated.

Chinese name

德天螺序草 (de-tian-luo-xu-cao in Mandarin).

Distribution and habitat

Until now, only two populations of the new species have been found. They are both known from limestone hills of southern Guangxi. Plants of the new species prefer to grow at humid places at elevation range of 500‒800 m, under evergreen broad-leaved forests with tree species of Fagaceae, Lauraceae, Tiliaceae, Theaceae, Myrsinaceae, Magnoliaceae and Sapindaceae.

Figure 1. 

Spiradiclis detianensis A habit B stipule C inflorescence, side view D opened long-style flower E opened short-style flower F capsule, side view G capsule under matured, face view. Scale bar: 1 cm (A, C, D, E); 2 mm (B, F, G). Drawn from the holotype by X.Y. Zeng.

Figure 2. 

Spiradiclis detianensis A habit B inflorescence C leaves D, E stipule F, G short- and long-styled flower, front view H opened long- and short-styled flower, showing style and stamens I ovary, side view J infructescence, side view. S. tubiflora K habit L inflorescence. Scale bars: 1 cm (B, C, H, J, L); 2 mm (D, E, F, G, I). Photos by Z.J. Wen and L. Wu.

Provisional conservation status

. During a series of field investigations at the China-Vietnam border over the past ten years (2009–2019), only three populations of Spiradiclis detianensis have been observed. One site with nearly 59 matured individuals is distributed in Detian Waterfall (type locality), while the other two sites with more than 250 and 114 individuals are in the Longzhou county and Ningming county, respectively. The habitats of the three sites are in good condition and have been rarely influenced by humans. Considering the above, the species can be assigned a status of ‘Least concern’ [LC] following the guidelines of IUCN (2019).

Discussion

Our unpublished molecular data indicates that Spiradiclis detianensis shows the closest genetic relationship with S. cordata. Both species prefer to grow on limestone hills from southern Guangxi, China, and have similar habit, such as short stems, subrosulate leaves, long peduncles, heterostylous flowers, funnel-shaped corollas and subglobose capsules. However, the former can be easily distinguished from the latter mainly by its leaf blade basally cuneate (vs. basally cordate) and corolla tubes 1.8–2.2 cm long (vs. ca. 5 mm long) (more detailed comparisons are listed in Table 1).

Table 1.

Morphological comparison of Spiradiclis detianensis, S. tubiflora and S. cordata Lo et W. L. Sha.

Spiradiclis detianensis S. cordata S. spathulata S. tubiflora
Habit rosulate to subrosulate rosulate to subrosulate rosulate procumbent to creeping
Leaf blade obovate-lanceolate or oblong, 7.0–10.5 × 2.0–3.5 cm, base cuneate, apex obtuse or acute elliptic-ovate to elliptic-oblong, 5–13 × 2–5.5 cm, base cordate, apex obtuse to rounded spatulate or obovate-oblanceolate, 8–13 × 2–4.5 cm, base acute to cuneate, apex obtuse to rounded ovate to elliptic, 0.5–2.5 × 0.4–1.5 cm, base rounded to obtuse, apex acute to rounded
Secondary vein 7–10 pairs 15–19 pairs 15–25 pairs 3–5 pairs
petiole 0.8–1.7 cm long 1–7 cm long 5–8 mm long 0.3–1.8 cm long
Stipule triangular, entire or bifid deeply 2-lobed, lobes linear lanceolate-linear or linear narrowly linear
Inflorescence cymose, one per plant, 2–7-flowered cymose to paniculate, 1–3 per plant, many flowered cymose, 10– to many flowered cymose, one per plant, 2–5-flowered
Peduncle 9–14 cm long 6–16 cm long 7–12 cm long 1.2–1.5 cm long
Bract linear-triangular, 4–6 mm long linear or subulate, 2 mm long linear-lanceolate, 3–4 mm long subulate, 1.8–3.0 mm long
Calyx lobe triangular, 1.2–2.9 mm long triangular, ca. 0.8 mm long narrowly lanceolate, 1–1.3 mm long triangular, 1.4–1.6 mm long
Corolla color Purple White purple-reddish white
Corolla tube tubular-funnelform, sharply enlarged at the 1/3 lower part of the corolla tube, 18–22 mm long tubular-funnelform, sharply enlarged at the middle or 1/3 upper part of the corolla tube, 5 mm long slenderly salverform, tube 15–25 mm long tubular-funnelform, slightly enlarged from the base to the throat, 14–16 mm long
Corolla inside (long-styled form) without villous ring with villous ring at middle with villous ring at middle Without villous ring

Spiradiclis detianensis is very similar to S. spathulata in morphology, since both have subrosetted habit, obovate-oblanceolate leaf blades, long peduncles and subglobose capsules, but it differs mainly by its corolla tubular-funnel shaped (vs. slenderly salver shaped), 4.5–6.8 (vs. 1.5–2) mm in diam. at the middle and densely pubescence inside corolla near base and densely puberulent above anther and onto lobes (vs. glabrous except a ring of long hairs at the middle) (more detailed comparisons are listed in Table 1).

Spiradiclis detianensis is a distinct species in the genus Spiradiclis due to the corolla tubes 18–22 mm long and having the shape of a reversed wine bottle, with an abruptly narrowed lower third, 4.5–6.8 mm in diam. at throat, 1.8–2.5 mm in diam. near base. Until now, only one other known species, S. tubiflora L.Wu, B.M.Wang & B.Pan (Wu et al. 2019b), has a similar corolla shape (see Fig. 2 K & L). However, S. detianensis differs from S. tubiflora principally by its rosulate habit (vs. procumbent to creeping), leaf blades longer than 7 cm and wider than 2 cm (vs. shorter than 2.5 cm and narrower than 1.5 cm), secondary veins 7–10 pairs (vs. 3–5 pairs) and longer corolla tubes (vs. 18–22 mm vs. 14–16 mm) (more detailed comparisons are listed in Table 1).

Additional specimens examined

(paratypes). China. Guangxi: Longzhou county, Nonggang National Nature Reserve, 2 April 2019 (fl.), Zheng-Quan Nong nzq0004 (CSFI); Niming county, Tingliang Town, Lixin village, 28 July 2011 (fr.), Yu-Song Huang 9422 (IBK).

Acknowledgements

The author is grateful to the curators of herbaria GSMI, IBSC KUN and PE for permission to examine specimens, and to Mr. Zheng-You Nong and Yu-Song Huang for their help in the field investigation. We also appreciate Ms. Xin-Yi Zeng for her excellent drawing. This study was supported by the Scientific Research Project of Education Department of Hunan Province (grant. no. 18B178).

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