Bot. Bull. Acad. Sin. (2005) 46: 377-383

LI et al. — Begonia rubinea, a new species from Guizhou, China

Begonia rubinea (sect. Platycentrum, Begoniaceae), a new species from Guizhou, China

Hong-Zhe LI^1,2, Hong MA^1,2, Kai-Yun GUAN^1,*, and Ching-I PENG^3,*

¹Kunming Institute of Botany, the Chinese Academy of Sciences, Kunming, Yunnan 650204, P.R. China

²Graduate School of Chinese Academy of Sciences, Beijing 100039, P.R. China

³Herbarium, Research Center for Biodiversity, Academia Sinica, Nangang, Taipei 115, Taiwan

(Received April 6, 2005; Accepted September 26, 2005)

Abstract. Begonia rubinea (sect. Platycentrum), a new species from Guizhou Province, China, is described and illustrated. Its chromosome number (2n = 22) and pollen morphology are reported. Begonia rubinea was collected from a small damp cliff in Changqiangou, Xishui National Reserve of Evergreen Arbor Forest, in Guizhou. It resembles B. smithiana T.T. Yü ex Irmsch. in aspect, but is distinct by the combination of the following characters: leaves thinly coriaceous and glossy, sparsely hispidulous; leaf margin entire or remotely shallowly denticulate; petioles glabrous; androecium zygomorphic, stamens few (15-30), androphore distinct, 2-3 mm long; and ovary glabrous or nearly so. Line drawings of B. rubinea and color photographs of both B. rubinea and B. smithiana are presented to aid in identification.

Key words: Begonia; Begonia rubinea; Begonia smithiana; Begonia sect. Platycentrum; China; Chromosome number; New species; Pollen morphology; Rare species.

Introduction

The genus Begonia (Begoniaceae) consists of ca. 1,400 species distributed mainly in tropical and subtropical regions (Smith et al., 1986; Doorenbos et al., 1998). China is endowed with a rich, diversified assemblage of Begonia. About 150 species of Begonia were recorded from China and classified into nine sections by Shui et al. (2002). Many new species, however, have been reported in the subsequent years, e.g., Tebbitt and Guan (2002), Shui (2002a, 2002b), Ye et al. (2004), Fang et al. (2004), Ku et al. (2004), Shui and Chen (2004, 2005), Xing et al. (2005), Peng et al. (2005a, 2005b, 2005c), and Liu et al. (2005).

Xishui National Reserve of Evergreen Arbor Forest lies in Xishui Xian, Guizhou Province, China, between 28°07'-28°34' N and 105°50'-106°29' E. It occupies an area of 48,666 ha, of which 89.6% is covered by vegetation. During the field expeditions to Xishui National Reserve of Evergreen Arbor Forest in November, 2002 and September, 2004, the first two authors collected several sterile individuals of a Begonia. These plants were brought into cultivation at the Kunming Botanical Garden, where they flowered and set fruits. After consulting local and national floras (Huang, 1989; Ku, 1999), other relevant literature (see

above) and abundant herbarium specimens and failing to find a name for it, we propose it as a new species, Begonia rubinea (sect. Platycentrum), which is described and illustrated here.

Species Description

Begonia rubinea H. Z. Li & H. Ma, sp. nov.—TYPE: China. Guizhou Province, Xishui Xian, Xishui National Reserve of Evergreen Arbor Forest, Changqiangou, alt. ca. 700 m, on a damp cliff, 8 Nov 2002; type specimens pressed from plants cultivated in Kunming Botanical Garden, H. Z. Li 87 (holotype: KUN; isotype: HAST).

¥É¬`¬î®ü´Å Figures 1, 2

Haec species nova differt a B. smithiana T.T. Yü ex Irmsch. foliis tenuiter coriaceis, sparsissime hispidulis (in illa membranaceis vel herbaceis, setoso-pilosis), margine integris vel remote denticulatis (in illa irregulariter duplo serrratis vel dentatis), petiolis glabris (in illa piloso-villosis), androecio zygomorpho (in illa actinomorpho), staminibus paucioribus 15-30 (in illa 40-85), androphoro distincto, 2-3 mm longo (in illa 1-2 mm), ovario glabro vel subglabro (in illa piloso vel setoso-villoso).

Herbs, perennial, acaulescent, monoecious. Rhizomes branched, creeping, internodes short, rooting at nodes. Stipules rose pink, membranous, glabrous, triangular, 5-7 mm long, 4-7 mm wide, margin entire, apex acuminate. Leaves 3 to many, all basal; petiole 13-31 cm long, ruby-red, glabrous; blade thinly coriaceous, obovate, 3-9 cm

*Corresponding author. Kai-Yun GUAN, E-mail: guangky@ public.km.yn.cn; Tel: +86-871-5223090; Ching-I PENG, E-mail: bopeng@sinica.edu.tw; Fax: +86-871-5219933; Tel: +886-2-2789-3821; Fax: +886-2-2789-1623.

Botanical Bulletin of Academia Sinica, Vol. 46, 2005

Figure 1. Begonia rubinea H. Z. Li & H. Ma. A, Habit; B, Portion of leaf, showing trichomes on adaxial surface; C, Stipule; D, Face view of staminate flower, D', Side view of staminate flower; E, Androecium; F, F', Anthers; G, Carpellate flower; H, I, Style and stigma; J, Capsule; K, Cross sections of capsule (From a living plant of H. Z. Li 87 in cultivation at HAST).

LI et al. — Begonia rubinea, a new species from Guizhou, China

Figure 2. Begonia rubinea H. Z. Li & H. Ma. A, Habit and habitat; B, Putative F1 hybrid individual between Begonia rubinea and B. pedatifida H. Lév; C, Cultivated plant at early anthesis; D, Leaf abaxial surface, showing rufous color; E, Face view of staminate flower; F, Side view of staminate flower; G, Androecium, showing a distinct androphore; H, Carpellate flower; I, Capsule; J, Middle cross section of capsule.

Botanical Bulletin of Academia Sinica, Vol. 46, 2005

long, 2-6 cm wide, base obliquely cordate, margin irregularly crenate, apex acuminate, adaxial surface emerald colored, sparsely white tribuloid when young, gradually glabrescent, veins wine colored, abaxial surface rufous, palmately 6-7 nerved, nerves sparsely rufous tribuloid. Inflorescence of symmetric dichasial cyme, flowers 3-5 in the cyme; peduncle 9-14 cm long, ruby-red, nearly glabrous; bract subulate, 10 mm long, 3 mm wide. Staminate flowers: pedicel ca. 7 mm long, pink; tepals 4, pink, in two whorls, outer two broadly ovate, 14-18 mm long, 13-15 mm wide, pilose outside; inner two lanceolate, 12-14 long, 5-6 mm wide; androecium zygomorphic, stamens 15-30, mostly pointing upward, filaments fused below into a distinct androphore 2-3 mm long. Carpellate flowers: pedicel 7-12 mm long, pink; tepals 5, pink, ovate, sparsely pilose outside; styles 2, connate below middle; stigmas bifid, helically contorted, papillate; ovary 2-locular. Capsule obovate-oblong, 7-8 mm long; wings 3, unequal, abaxial one ligulate, apex obtuse, glabrous, other two narrower, crescent-shaped, nearly in one plane. Seeds many, brown.

Ecology. Moist sandstone rocks in evergreen forests on a mountain at about 700 m elevation.

Etymology. The specific epithet `rubinea' refers to the ruby-red petioles.

Distribution. Northern Guizhou, China (Figure 3); known only from the type locality.

Phenology. Not observed in the wild. Plants in cultivation in the Kunming Botanical Garden flower from June to August and set fruit from September to November.

Chromosome Cytology. Begonia rubinea has a somatic chromosome number of 2n = 22 (Figure 4: A), which agrees with reports for several other species in Begonia sect. Platycentrum (Oginuma and Peng, 2002; Shui et al., 2002; Tian et al., 2002; Nakata et al., 2003; Ye et al., 2004; Li et al., 2005) in China. The chromosomes are small, ranging from 0.712 to 1.38 µm in length. The position of the centromeres was not discernible.

Pollen morphology. Pollen is elongate-ellipsoid, ca. 30 µm long, 13 µm in diam., tricolporate (Figure 4: B). Exine with irregular stripes and dotted with foveolae, which are denser in the polar areas.

Notes. The new species resembles Begonia smithiana T.T. Yü ex Irmsch. (Figure 5) in aspect, but is distinct in having thinly coriaceous and glossy, sparsely hispidulous leaves, leaf margin entire or remotely shallowly denticulate, glabrous petioles, zygomorphic androecium, stamens few (15-30), androphore distinct, 2-3 mm long, and the ovary glabrous or nearly so. We noted that plants of B. rubinea in cultivation produced longer petioles than those in the wild. The morphology of B. rubinea and B. smithiana is compared in Table 1.

Begonia rubinea is an epipetric species on sandstone rocks. Plants of B. pedatifida H. Lév. were abundant in its vicinity. A plant showing intermediate leaf form, presumably representing an F₁ hybrid individual between the two species, was also collected (Figure 2: B). Further studies to verify its putative parentage are in progress.

Acknowledgments. We thank Yu Chen and Jin-Mei Lu (KUN) for assistance in the field expedition in 2002; Masashi Nakata and Makoto Hashiya (TYM) for taking pollen SEM microphotographs; Hidetoshi Nagamasu (KYO) for the Latin description; Ya-Wen Hsueh (HAST) for the handsome line

Figure 3. Distribution of Begonia rubinea (star) in Guizhou Province, China.

Figure 4. A, Metaphase somatic chromosome of Begonia rubinea (2n = 22); B, Pollen SEM microphotograph (From H. Z. Li 87, KUN).

LI et al. — Begonia rubinea, a new species from Guizhou, China

Figure 5. Begonia smithiana T.T. Yü ex Irmsch. A, Habit and habitat; B, Cultivated plant at early anthesis; C, Portion of leaf, showing leaf margin and pubescence; D, Early inflorescence; E, Staminate flower; F, G, Carpellate flower, side view and face view; H, Ovary, cross section.

Botanical Bulletin of Academia Sinica, Vol. 46, 2005

Peng, C.-I, Y.K. Chen, and W.C. Leong. 2005a. Five new species of Begonia (Begoniaceae) from Taiwan. Bot. Bull. Acad. Sin. 46: 255-272.

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Ye, H.G., F.G. Wang, Y.S. Ye, and C.-I Peng. 2004. Begonia coptidifolia (Begoniaceae), a new species from China. Bot. Bull. Acad. Sin. 45: 259-266.

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LI et al. — Begonia rubinea, a new species from Guizhou, China