Spiradiclis danxiashanensis R. J. Wang, 2015

Wang, Rui-Jiang, Wen, Hai-Zhen, Deng, Shu-Jun & Zhou, Lian-Xuan, 2015, Spiradiclis danxiashanensis (Rubiaceae), a new species from South China, Phytotaxa 206 (1), pp. 30-36 : 31

Spiradiclis danxiashanensis R. J. Wang , sp. nov. ( Figs. 1 & 2 : A–E)

Type: — CHINA. Guangdong province: Shaoguan City, Renhua County, Mt Danxiashan, 25°01’ N, 113°44’ E, 145 m, 13 April 2011, short-styled flower, R.- J. Wang & H.- Z. Wen 1548 (holotype IBSC!, isotypes IBSC!).

Spiradiclis danxiashanensis is similar to S. guangdongensis , from which it differs in having concolorous leaves with acute to acuminate apices, 4–5(–6) pairs of secondary veins, smooth projections at the periclinal walls of leaf epidermal cells, and cymose inflorescences with (1–)2–3 flowers.

Perennial herbs, prostrate or decumbent, rooting at basal nodes; stems terete, slender, sparsely pubescent. Stipules entire or bipartite, lobes linear, 2–5 mm long.Petiole 4–12 mm long, sparsely pubescent; leaf blades ovate, 0.5–2.4 (–3.3) × 0.5–1.5 (–2) cm, base truncate to rounded, apex acute to acuminate, papery, margin densely ciliate, adaxially sparsely hispidulous, abaxially usually glabrous or subglabrous, light green, concolorous both sides; secondary veins 4–5 (–6) on each side; leaf epidermal cells irregularly polygonal on adaxial side, 62.3 × 29.3 μm, anticlinal walls sinuous, periclinal walls with large and smooth irregular projections; abaxial cells irregularly polygonal, 72.5 × 34.0 μm, anticlinal walls sinuous, periclinal walls with large and smooth irregular projections; stomata paracytic ( Fig. 3 : A – C). Inflorescence terminal, cymose, (1–) 2–3-flowered; peduncles sparsely puberulent, 1.3–2.8 cm long; bracteoles linear, 2.5–4.3 mm long. Flowers sessile or short-pedicellate, distylous, 5-merous; pedicels (when present) sparsely puberulent, to 5.0 mm long. Hypanthium obconical, 0.5–1.5 mm long, sparsely puberulent to glabrescent; lobes lanceolate, 2.3–3.2 × 0.6–1 mm, glabrous, with inconspicuous glands at each sinus. Corolla salverform, white, subglabrous abaxially, tube 1.1–1.5 cm long, 0.6–1.5 mm wide; lobes subovate, 5.0–8.7 × ca. 3.5 mm; stamens 5; anthers oblong-linear, 1.6–3.0 mm long; stigma bilobed. Long-styled flowers: corolla tube subglabrous, densely pubescent on throat inside; stamens included, filaments adnate to the lower corolla tube, ca. 1.5 mm long; styles exserted, 1.8–2.1 cm long, stigmas capitate. Short-styled flowers: corolla tube sparsely pubescent inside but densely on throat; stamens exserted, filaments adnate to the upper portion corolla tube, 5–6 mm long; styles included, 6–9 mm long, stigmas linear. Capsules ovoid to subglobose, 1.3–1.9 mm long, with persistent calyx lobes. Seeds ca. 0.6 mm long, deep brown or black, angular. Pollen grains released in monads; isopolar; round-triangular at polar view; spheroidal, 29.3 (28.2–31.1) × 28.3 (27–30.5) μm in short-styled flowers, 27.5 (26–28.6) × 25.6 (23.5–27.7) μm in long-styled flowers, with 1.1 P / E value; 3-colporate; tectum microreticulate ( Fig. 3 : G – L).

Distribution and habitat: —Known only from Mt Danxiashan, the type locality. It grows commonly on hill slopes in understory vegetation of secondary forests.

IUCN Conservation assessment: — Spiradiclis danxiashanensis is only known from the type locality, although it is very common under forest at the lower land area of Mt Danxiashan World Geological Park. There are no significant or plausible threats because of the strict protection. It is therefore classified as Least Concern (LC), according to the guideline 8.1 of the IUCN Standards and Petitions Subcommittee (2014).

Phenology: —Flowering in March–April and fruiting in April–July.

Additional specimens examined (paratypes): — CHINA. Guangdong province: Shaoguan city, Renhua County, Mt Danxiashan , 14 November 1973, C.- C. Huang & Y.- T. Chang 038 ( IBSC, paratype of S. guangdongensis with typo error “ 34 ”) ; ibid., September 1980, H.- S. Lo 1447 ( IBSC, paratype of S. guangdongensis ) ; Mt Danxiashan, roadside in the Zhanglaofeng Scenic Area , 113°44’ E, 25°01’ N, 103 m, 24 May 2010, R.- J. Wang 1326 ( IBSC) ; Mt Danxiashan, hill slope nearby the Telpher Station , 113°44’ E, 25°02’ N, 91 m, 13 April 2011, R.- J. Wang & H.- Z. Wen 1546, 1547, 1549 ( IBSC) ; ibid., 11 May 2011, R.- J. Wang & H.- Z. Wen 1592 ( IBSC) ; Mt Danxiashan, hill slope nearby the entrance of Zhanglaofeng Scenic Area , 113°44’ E, 25°02’ N, 147 m, 22 April 2014, R.- J. Wang 2674, 2675 ( IBSC) .

Taxonomic notes: — Spiradiclis danxiashanensis is similar to S. guangdongensis in leaf size, corolla color and shape, but differs in habit, leaf color and shape, number of secondary veins, morphological pattern of epidermal cells, and flower number per inflorescence ( Table 1). The separation of S. danxiashanensis from S. guangdongensis makes it necessary to provide an emendation to the description of S. guangdongensis ( Lo 1987) . In addition, the characters of long- and short-styled flowers are supplemented. Apparently S. danxiashanensis is also similar to S. hainanensis H. S. Lo (1987: 301) , but the latter has cordate leaf bases and densely pubescent stem, petioles, abaxial side of leaf blade, peduncles, and abaxial side of calyx. Moreover, the flowering season of S. hainanensis is in October, while S. danxiashanensis is in March and April.

Figures

FIGURE 1. Spiradiclis danxiashanensis. A. Habit. B. Stipules, adaxial (left) and abaxial (right) views. C. Dissected short-styled flower, showing stamens and hairy corolla throat. D. Style of short-styled flower, showing the linear bilobed stigma. E. Dissected long-styled flower, showing the stamens and hairy throat. F. Style of long-styled flower, showing the capitate stigma. G. Inflorescence of long-styled flowers. H. Capsule (A–D, H from the type; E, F, and G from R.-J. Wang & H.-Z. Wen 1547). Drawn by Ms Yun-Xiao Liu.

FIGURE 2. Morphological characters of Spiradiclis danxiashanensis (A–E) and S. guangdongensis (F–J). A, F. Habit. B, G. Leaves. C, H. Long-styled flowers. D, I. Short-styled flowers. E, J. Young capsules. Photos by Rui-Jiang Wang

FIGURE 3. Micro-morphology of leaf and pollen of Spiradiclis danxiashanensis and S. guangdongensis. A–C. showing adaxial and abaxial epidermis and stomata of S. danxiashanensis (from R.-J. Wang & H.-Z. Wen 1549), respectively. D–F. showing those of S. guangdongensis (from R.-J. Wang, X. Guo, S.-J. Deng 1689), respectively. G–I. showing equatorial and polar views and microreticulate surface of pollen grains of long-styled flowers of S. danxiashanensis (from R.-J. Wang & H.-Z. Wen 1547), J–L. showing those of short-styled flowers of S. danxiashanensis (from R.-J. Wang & H.-Z. Wen 1546), and M–O. showing those of long-styled flowers of S.