Begonia abbreviata, Peng, Ching-I, Yang, Hsun-An, Kono, Yoshiko, Jung, Ming-Jer & Nguyen, Tien Hiep, 2015

Peng, Ching-I, Yang, Hsun-An, Kono, Yoshiko, Jung, Ming-Jer & Nguyen, Tien Hiep, 2015, Four new species of Begonia (Begoniaceae) from Vietnam: B. abbreviata, B. calciphila, B. sphenantheroides and B. tamdaoensis, Phytotaxa 222 (2), pp. 83-99 : 86-89

1. Begonia abbreviata C.-I Peng, sp. nov. (sect. Petermannia ) ( Figs 1 , 2 )

Type: — VIETNAM. Quang Tri Province, Dakrong District , Trieu Nguyen Commune. Sterile plants collected by Pi-Fong Lu on 4 Nov 2009 ; type specimen made from the collection cultivated in the experimental greenhouse, Academia Sinica, 3 July 2010, Peng 22355 (holotype: HAST 139792 ; isotypes: E, HN) Ž Ḣkȁầ

Herbs perennial, monoecious. Rhizomes green or reddish, terete, 6–8 mm across, to 10 cm or longer, creeping, appressed reddish pubescent, internodes 1–4 cm long. Stipules triangular, 1.3–1.8 cm long, ca. 7 mm wide, puberulent, apex acuminate and cuspidate, cusp 3 mm long, margin entire. Leaves alternate; petiole 2–5 cm long, 3–4 mm across, appressed pubescent; leaf blade ovate to broadly ovate, apex acute to mucronulate, base obliquely cordate, margin entire, 6–17 cm long, 5–12 cm wide; adaxially green or with many silver white patches in intercostal regions; patches elliptic, to 8 mm long, 5 mm wide, minutely puberulent; abaxially reddish tomentulose on red veins and veinlets; primary veins palmate, dichotomous, veinlets reticulate. Inflorescence unisexual or bisexual, in cymosely branching panicle, protogynous, axillary and terminal on the rhizome, erect, reddish, subglabrous, peduncles 0.5–1.5 cm long; female inflorescence 1–3-flowered, male inflorescence single or branched, flowers 5–30. Flowers scented. Bracts reddish, persistent, narrowly ovate at base of inflorescence, ca. 13–18 mm long, 6 mm wide, apex acute, margin ciliate; widely ovate at summit of inflorescence (with staminate flowers), 6–8 mm long, ca. 6 mm wide, margin ciliate. Staminate flower: pedicel 2.5–3 cm long, tepals 4, outer 2 white or pinkish, with apparent red veins, orbicular to ovate, 1.2–1.5 cm long, 1–1.2 cm wide, margin entire, abaxially sparsely reddish-scabrescent or subglabrous; inner 2 white or pinkish, oblanceolate, apex round, base cuneate, 0.9–1.2 cm long, ca. 3 mm wide, glabrous; androecium actinomorphic, stamens 40–52, yellow, filaments free, ca. 0.7 mm long, anthers ca. 1 mm long. Carpellate flower: pedicel 0.5–1 cm long, tepals 5, white or pinkish, with apparent red veins, suborbicular to narrowly oblanceolate, outer 3 suborbicular to broadly obovate, ca. 1 cm long, 0.7–1 cm wide, abaxially sparsely reddish-scabrescent; inner 2 unequal, obovate to narrowly so, ca. 1 cm long, 3–6 mm wide, glabrous; ovary trigonous-ellipsoid, sparsely reddish hirsute, 3-locular, 3-winged, wings subequal, ca. 5 mm tall, placentation axile; styles 3, ca. 5 mm long, each forked at middle, stigmatic band spiralled. Capsule trigonous-ellipsoid, 0.9–1.6 cm long, 5–8 mm across, wings trapeziform with rounded tips and entire margin, 5–7 mm tall.

Ecology and distribution:— Endemic to northern Vietnam, Quang Tri Province ( Fig. 3 ).

Etymology:— The specific epithet refers to the short peduncle in the new species.

Additional specimen examined:— VIETNAM. Thua Thien Hue Province, elev. 500– 600 m. Under broad-leaved evergreen forest, on soil, wet place, very common, 7 June 2004, Nguyen Tien Hiep 5917 (HN).

Leaf anatomy and vestiture:— Adaxial surface with sparse glandular trichomes ( Fig. 4A ); cross section ca.320 μm thick, epidermis single-layered on both surfaces, hypodermis absent ( Fig. 4B ); abaxial surface with glandular trichomes, stomata complex single, helicocytic, slightly elevated, subsidiary cells (8–)9(–11) ( Fig. 4C ).

Chromosome cytology:— Somatic chromosomes at metaphase of Begonia abbreviata were determined to be 2 n = 30 ( Fig. 5A ). The thirty chromosomes gradually varied from ca. 1.0 to 1.6 μm long. Several longer chromosomes have centromeres at median or submedian positions. Satellites were not observed.

Asian Begonia section Petermannia comprises ca. 250 species ( Doorenbos et al. 1998; Hughes 2008).Chromosome numbers of only six of them (ca. 2.4 %) were previously reported: 2 n = 30 (3 spp.) and 2 n = 44 (3 spp.) ( Legro and Doorenbos 1969, 1971, 1973). We have examined chromosomes of 14 species in sect. Petermannia (unpublished data), twelve of which had 2 n = 30, one had 2 n = 60 ( B. holttumii Irmscher (1929: 113)) , probably a tetraploid based on n =15, and one with 2 n =44 ( B. bipinnatifida J. J. Smith (1906: 47)) .

Notes:— Begonia abbreviata appears to be allied to B. eberhardtii Gagnepain (1919: 198) , which was known only from a single collection made about a century ago from Vietnam. Both species are members of sect. Petermannia with elongate rhizomes and lacking upright stems. However, they differ markedly in leaf shape. In B. abbreviata , leaves are broadly ovate with entire margin and an acute apex. By contrast, leaves of B. eberhardtii are ovate, with irregularly and coarsely dentate margin and an acuminate apex.

Figures

FIGURE 1. Begonia abbreviata C.-I Peng. A, Habit; B, Leaf adaxial surface; B’, Leaf abaxial surface; C, Petiole; D, Stipule; E, E’, Bracts; F, Staminate flower, face view; F’, Staminate flower, back view; G, Androecium; H, H’, Stamen; I, Carpellate flower, face view; J, Style and stigma; K, Cross section of ovary; L, Capsule.All from C.-I Peng 22355 (HAST). Line drawing by Ya-Wen Hsueh and Ming- Chao Yu.

FIGURE 2. Begonia abbreviata C.-I Peng. A, Habit and habitat; B, Cultivated plant at anthesis; C, Male inflorescence; D, Bisexual inflorescence, also showing leaf abaxial surface; E, Stipules; F, Male inflorescence with numerous staminate flowers; G, Female inflorescence; H, Carpellate flower, face view; I, Staminate flower, face view; J, Carpellate flower (side view), young fruit and bracts; K, Cross section of ovary. [A–D, H–I, K from C.-I Peng 22355 (HAST); E–G, J from NTH 5917(HN)].

FIGURE 3. Distribution map of Begonia abbreviata (■), B. calciphila (Ì), B. sphenantheroides (●) and B. tamdaoensis (▲) in Vietnam.

FIGURE 4. SEM microphotographs of Begonia leaves. A–C, B. abbreviata; D–F, B. calciphila; G–I, B. sphenantheroides; J–L, B. tamdaoensis; A, D, G, J, Leaf adaxial surfaces; B, E, H, K, Leaf cross-sections; C, F, I, L, Leaf abaxial surfaces. Scale bars = 200 μm.

FIGURE 5. Somatic chromosomes at metaphase of Begonia. A. B. abbreviata (2n = 30: NTH 5917); B. B. calciphila (2n = 30: Peng et al. 20226); C. B. sphenantheroides 2n = 22: Peng et al. 20216); D. B. tamdaoensis (2n = 18: Peng et al. 16638); B’, C’, D’, somatic chromosomes serially arranged by chromosome length and centromere position. Scale bars: B’, C’= 2 μm; D’ = 5 μm. Large arrows indicate a pair of the largest metacentric chromosomes with secondary constrictions (SC) at interstitial regions of the long arms; medium arrows indicate metacentric chromosomes with SC at distal regions of the long arms. Small arrows, large arrowheads and small arrowheads indicate metacentric chromosomes, subtelocentric chromosomes and telocentric chromosomes, respectively.