Introduction
Following extensive field surveys and herbarium-based studies (ABD, BK, BKF, BM, C, E, HAST, K, L, PSU and SING) for the Flora of Thailand project, 47 accepted names in Begonia L. representing eight sections of the genus were reported in the most recent checklist for Thailand (Phutthai et al., Reference Phutthai, Sands and Sridith2009). Eight new species and a new record (Phutthai & Sridith, Reference Phutthai and Sridith2010; de Wilde et al., Reference De Wilde, Hughes, Rodda and Thomas2011; Phutthai et al., Reference Phutthai, Hughes and Sridith2012, Reference Phutthai, Hughes and Sridith2014; Phutthai & Hughes, Reference Phutthai and Hughes2016; this study) have brought the total to 55 native species.
Begonia sect. Diploclinium (Lindl.) A.DC. is one of the largest sections of Asian Begonia, comprising 116 species (Hughes et al., Reference Hughes, Moonlight, Jara and Pullan2015), and is distributed from the Himalayas to Indochina and Malaysia (Doorenbos et al., Reference Doorenbos, Sosef and de Wilde1998). Rhizomatous species from the Philippines previously included in the section have recently been transferred to Begonia sect. Baryandra A.DC. (Rubite et al., Reference Rubite, Hughes, Alejandro and Peng2013), leaving the section somewhat better defined as a tuberous group with bifid placentae, the bulk of the species being restricted to continental Asia. The section as currently circumscribed is paraphyletic, other species of tuberous sections Alicida C.B. Clarke and Reichenheimia (Klotzsch) A.DC. being nested within it (Thomas et al., Reference Thomas, Hughes, Phutthai, Rajbhandary, Rubite, Ardi and Richardson2011). Begonia sect. Diploclinium is represented by 15 species in Thailand (Hughes, Reference Hughes2008; Phutthai & Sridith, Reference Phutthai and Sridith2010; Phutthai et al., Reference Phutthai, Hughes and Sridith2014). Three new species in the section, Begonia exposita Phutthai & M.Hughes, B. pengchingii Phutthai & M.Hughes and B. pseudosubperfoliata Phutthai & M.Hughes, are described here, bringing the number of Thai species in the section to 18. One of the species, Begonia pseudosubperfoliata, is aberrant in sect. Diploclinium in having a single placental branch per locule. However, classification in a different section based on this single, homoplastic character is not desirable (Thomas et al., Reference Thomas, Hughes, Phutthai, Rajbhandary, Rubite, Ardi and Richardson2011), and in all other respects it fits comfortably alongside other Thai members of the section.
Begonia sect. Apterobegonia Warb. was a rather poorly known monotypic section, being based on a description of a single specimen of a single species (Doorenbos et al., Reference Doorenbos, Sosef and de Wilde1998), namely B. delicatula Parish ex C.B.Clarke. Here we add another species, Begonia phutthaii M.Hughes, obviously allied to the type species in habit and leaf shape, and sharing the distinctive narrow wings on the fruit capsule. The new species extends the distribution of the section from Myanmar into Thailand.
Materials and Methods
The new species were described from observations of living plants in the wild, photographs thereof and herbarium material. Herbarium specimens were examined at first hand when necessary, and also via electronic images from Hughes et al. (Reference Hughes, Moonlight, Jara and Pullan2015). The placement of the species into the threat categories specified by the International Union for Conservation of Nature (IUCN) was carried out using the criteria in IUCN (2012), based on information from specimens and field observations.
Species Descriptions
Begonia exposita Phutthai & M.Hughes sp. nov. Sect. Diploclinium. Figs 1 , 2 .
The habit resembles that of Begonia putii Craib, B. discreta Craib and B. soluta Craib in terms of the small number of cordate leaves arising directly from a tuber. Begonia putii and B. soluta differ in being smaller plants, with leaves less than 6 × 6 cm (not up to 15 × 14 cm), and having 4 tepals in the male flowers (not 2). Begonia discreta is a more similar size to B. exposita but differs in having fewer stamens (c.12, not 40–50) and male flowers with 4 tepals (not 2), and in being a higher altitude species (found at c.1350 m, not c.140 m altitude). Begonia exposita further differs from all three species in having succulent leaves (not thin and papery). – Type: Thailand, Sangkhla Buri District. On exposed limestone in direct sunlight area, 15°18′N, 98°23′E, 140 m, 4 x 2009, T. Phutthai 222 (holo BKF; iso E, PSU).
Begonia exposita Phutthai & M.Hughes. A, Habit and habitat of exposed limestone (Phutthai 262); B, tuberous stem; C, pubescent hairs on petioles; D, minute pubescent hairs on lamina and leaf margin; E, hairs on bracts and outer tepals; F, inflorescence; G, male flowers; H, female flowers; I, capsule (B–E from Phutthai 222).
Distribution of Begonia phutthaii (triangles), B. pengchingii (circle), B. pseudosubperfoliata (square) and B. exposita (star).
Monoecious acaulescent herb, 10–30 cm tall. Tuber globose or cordiform, c.5–10 mm in diam., with numerous fibrous roots. Leaves unifoliate, lamina basifixed; petiole dark red, pubescent, reddish brown when dry, 9–15 cm long; leaf blade succulent, subcoriaceous, symmetrical, adaxial surface pubescent, glossy light green, abaxial surface pubescent, pale green; ovate, 3–15 × 4–14 cm, base deeply cordate, apex acute, margin serrate and ciliate; venation palmate, veins 12–14, prominent beneath. Stipules deciduous. Inflorescences arising from tuber, compound cymes, branched up to 4 times, bisexual, 20–30 cm long, staminate flowers basal and pistillate flowers distal, protandrous; peduncles 10–26 cm long, terete, glabrous, dark red, glossy. Bracts ovate, margin fimbriate. Staminate flowers: pedicels dark red, 3–4 mm long, sparsely hairy, erect or occasionally ascending; tepals 4, white with a pale pink flush inside and outer part darker, bright pink on the reverse; outer 2 suborbicular, c.6 × 6 mm, base rounded, margin entire, apex rounded, sparsely hairy on the reverse, inner side glabrous, inner 2 narrowly elliptic, c.5 × 2 mm; androecium actinomorphic, globose, stamens 40–50, bright yellow, filaments fused at the base, c.1 mm long, anthers oblong, c.1 mm long, dehiscing by short slits near the tip. Pistillate flowers: pedicels pale green, sparsely hairy, 2–3 mm long; tepals 2(or 3), same colour as staminate flower; suborbicular, 5–8 × 5–9 mm, base rounded, margin entire, apex rounded, outer parts sparsely hairy, inner parts glabrous; styles 3, fused at the base, dark yellow, stigmatic band crescent-shaped and minutely papillose; ovary green or pink, with 3 subequal wings; 3-locular, placentation axillary, 2 branches per locule. Fruits capsules, glossy, pale green, drying pale brown, 10–15 × 4–5 mm; locules subglobose, 4–5 × 4–5 mm, abaxial wing ligulate with a rounded apex, c.10 mm long, 5–6 mm wide at base, 2 lateral wings deltoid, 2–3 mm long, 5–6 mm wide at base.
Distribution
Endemic to Southwestern Thailand, Kanchanaburi Province, Sangkhla Buri District; growing on an inselberg limestone mountain near Three Pagodas Pass between Thailand and Myanmar.
Habitat and ecology
On exposed limestone rock crevices at an altitude of 140 m. Flowering May to November; fruiting November to January.
Notes
Begonia exposita is endemic to Thailand and a very rare species. Only two other Begonia species can be found in a similar, exposed limestone habitat in Thailand, namely B. alicida and B. soluta. This habitat is unusual for Begonia, being comparatively hot and dry, especially in the dry season. Such habitats can be found only in the north of the Tenasserim range in Kanchanaburi Province. The species is able to grow only on degraded limestone on a rather small flat area. The specific epithet relates to the exposed habitat of the species.
Proposed IUCN category
The new taxon is found only in the type locality, in a very rare and unusual habitat within Thailand, namely exposed limestone in Sangkhla Buri District, Kanchanaburi Province. The observed expansion of a road next to the type locality may have a negative impact on Begonia exposita in the near future. Moreover, the site of the mentioned species is not a protected area. Hence, we consider Begonia exposita to be Vulnerable under the VUD2 criterion.
Begonia pengchingii Phutthai & M.Hughes sp. nov. Sect. Diploclinium. Figs 2 , 3 .
A distinct species, closest to Begonia discreta in having 1 or 2 elongate-cordate symmetrical or subsymmetrical leaves and inflorescence arising from the tuber. It differs in having 2 tepals in the staminate flowers (not 4), variegated leaves, and one enlarged abaxial wing on the fruit, with the others reduced to small ridges (not 3 subequal wings). The leaf variegation is very similar to that in Begonia curtisii Ridl., but that species (in sect. Parvibegonia A.DC.) has asymmetrical leaves and 2-locular fruit. – Type: Thailand, Chiang Rai, Mae Sai District. On limestone cliff face in deep shade of summit cliff, 1350 m, 30 x 2005, C.-I Peng, C.-I Huang, J.F. Maxwell & P. Palee 20670 (holo HAST; iso BKF, E).
Begonia pengchingii Phutthai & M.Hughes. A, Habit and habitat; B, adaxial and abaxial lamina; C, inflorescence; D, mature capsules (all from Peng et al. 20670).
Perennial monoecious herb, 10–20 cm tall. Tubers globose or subglobose, c.10 mm in diam., with numerous fibrous roots. Stems succulent, glossy, erect or suberect, with sparse multicellular hairs, dark red. Leaves only 1 or 2 per plant, basifixed, arising from the tuber or 1 or 2 cauline leaves present subtending the inflorescence; petiole dark red, 3.5–7 cm long; leaf blade succulent, subsymmetrical, chartaceous when dry, adaxial surface with sparse multicellular hairs, dark green or brownish–dark green with a silver band running inside the margin, glossy, abaxial surface pale purplish red or vinaceous, with dense multicellular hairs especially on veins, cordate, 6–13 × 3–10 cm, base cordate, apex acute, margin sinuate or remote sinuate with multicellular hairs, venation palmate-pinnate, veins 6–8. Stipules not seen. Inflorescences arising directly from tuber, polychasium, bisexual, branched 1 or 2 times, 9–13 cm long, with many staminate flowers and 2 pistillate flowers per branch, protandrous; peduncles terete, 3–14 cm long, pale green or dark red, glossy, glabrous. Bracts not seen. Staminate flowers: pedicels 3–10 mm long, erect; tepals 2, white, ovate, c.7 × 4 mm, base rounded, apex obtuse, margin entire, sparse dark red multicellular glandular hairs on outsides, glabrous inside; androecium zygomorphic, stamens 10–15, yellow, filaments c.1 mm long, anthers obovate, c.1 mm long, dehiscing by longitudinal slits near the tip, filaments fused at the base. Pistillate flowers not seen; ovary with 1 wing and 2 small ridges; 3-locular, placentation axillary, 2 branches per locule. Fruits dehiscent, glossy, pale green, pendulous, drying pale brown; capsule locules ellipsoid, 15–20 × 5 mm, abaxial wing obliquely triangular tapering at the end of the fruit body, 10–15 mm long, 2 lateral wings reduced to ridges.
Distribution
Endemic to Northern Thailand; Chiang Rai Province, Mae Sai District, Huay Krai Subdistrict, in front of Doi Tung Temple.
Habitat and ecology
On limestone rock crevices in seasonally dry evergreen forest at an altitude of 1350 m. Flowering May to November; fruiting November to January.
Notes
Begonia pengchingii has an unusual fruit with only one oblique triangular wing, which is unique in Begonia section Diploclinium; most other species have three subequal wings. The zygomorphic androecium and staminate flowers with two tepals are also unusual in the section, with only five members of the section having the latter (Doorenbos et al., Reference Doorenbos, Sosef and de Wilde1998). The epithet pengchingii honours Dr Ching-I Peng, who first collected the species.
Provisional IUCN category
VUD2. Begonia pengchingii is restricted to karst limestone and known only from the type locality in the environs of the Phra That Doi Tung Temple, which although not a formally protected area should be safe from destruction by mining because of its status as a sacred area. However, shifting cultivation, as sometimes practised by farmers in nearby villages, can drastically alter the microhabitat of karst vegetation, especially in terms of causing reduced shade and humidity (Kiew, Reference Kiew2001; Clements et al., Reference Clements, Sodhi, Schilthuizen and Ng2006). Karst limestone areas can also attract tourists in large numbers, which can lead to habitat degradation. Therefore, we consider B. pengchingii to be vulnerable to human activities and assign the Vulnerable category under criterion D2.
Begonia phutthaii M.Hughes sp. nov. Sect. Apterobegonia. Figs 2 , 4 .
Differs from the allied Begonia delicatula in having caducous (not persistent) stipules, a denser indumentum over all vegetative parts (B. delicatula has glabrous stems, not densely hairy, and leaves with scattered, not dense hairs). The leaf lamina of Begonia delicatula is orbicular-reniform, whereas in B. phutthaii it is orbicular-ovate; the lamina margin of B. phutthaii is acutely dentate, whereas in B. delicatula it is shallowly and broadly crenately lobed and denticulate. The basal lobes of the lamina overlap in Begonia phutthaii, and do not overlap in B. delicatula. – Type: Thailand, Mae Hong Son, Pang Ma Pha District, Road between Pai and Pang Ma Pha. On vertical limestone in deep shade of dry evergreen forest on limestone, 19°30′8.3″N, 98°16′41.5″E, 632 m, 22 x 2014, D.J. Middleton, C. Hemrat, P. Karaket, C. Puglisi & S. Suddee 5822 (holo E; iso BKF, SING).
Begonia phutthaii M.Hughes. A, Habit, habitat and inflorescence (Middleton et al. 5827); B, adaxial lamina; C, abaxial lamina; D, female flower (Middleton et al. 5822); E, male flowers and; F–G, mature capsules; H, ovary, middle cross-section (B, C, E and F–H from Phutthai 263).
Monoecious herb, 10–30 cm tall. Tubers globose or subglobose, 5–10 mm in diam., with numerous fibrous roots; stems succulent, glossy, erect or suberect, densely pubescent, pale green or pale purple-red. Leaves 6–8 per plant, basifixed, alternate; petiole pale green, or pale to dark claret, reddish brown when dry, 5–20 cm long; leaf blade chartaceous, asymmetrical, broadly ovate, 4–13 × 4–14 cm, base cordate, apex acute, margin irregularly dentate, venation palmate, veins 7 or 8, adaxial surface densely pubescent, dull light green or vinaceous-greenish, glossy, abaxial surface densely hairy especially on veins, green or dark vinaceous. Stipules persistent, pale green or pale vinaceous, triangular, 4–5 × 2–2.5 mm, apex acute, margin entire, hairy. Inflorescences terminal, compound cymes, bisexual, branched 1–4 times, 4–13 cm long, with 4–6 staminate flowers and 2 pistillate flowers per branch, protandrous; peduncles 3–5 cm long, terete, densely pubescent, glossy. Bracts caducous, membranous, lanceolate, c.1–2 × 0.5–2 mm, greenish pink, pale green, glossy, apex acute or obtuse, margin entire, pubescent. Staminate flowers: pedicels 5–10 mm long, erect (or ascending); tepals 2 or 4(–5), crimson or pale pink or white; outer 2 orbicular, 4–10 × 5–10 mm, base rounded, apex obtuse or acute, margin entire, glabrous inside, hairy outside; inner 2 oblong, 4–5 × 2 mm, base cuneate, apex obtuse, margin entire, glabrous on both sides; androecium actinomorphic, globose, stamens 40–50, yellow, filaments c.0.5 mm long, fused to androecium, anthers c.0.5 mm long, oblong, dehiscing by short slits near the tip. Pistillate flowers: pedicels pale crimson, 6–9 mm long; tepals 2–4(–5), same size and colour as the staminate flowers; styles 3, fused at the base, stigmatic band kidney-shaped, surface once spirally twisted, yellow; ovary with 3 equal wings, pink or very pale green, densely pubescent; 3-locular, placentation axillary, 1 branch per locule. Fruits: capsules, pinkish white, pendulous, drying pale brown, 5 × 5–6 mm, dehiscent at the end of the wings; locules ovoid, 4–5 × 3–4 mm, 3 equal wings, crescent-shaped.
Distribution
Endemic to Northern Thailand; Mae Hong Son and Chiang Rai Provinces.
Habitat and ecology
On damp and shaded limestone cliffs in seasonally dry evergreen forest. Flowering May to November; fruiting November to January.
Notes
The specific epithet phutthaii is was coined by the second author of this manuscript, in recognition of the first author's endeavours in the field and herbarium which have done so much to increase our understanding of Thai Begonia. The tepal number and shape varies within populations in this species; the type locality has individuals with both 2 and 4 (or 5) tepals in the male and female flowers, with either acute or obtuse apices. Moreover, the leaf colour in different populations in Chiang Rai and Mae Hong Son Provinces varies from pale light green to dark vinaceous according to light, shading and soil composition.
Proposed IUCN category
Vulnerable (VUD2). Currently known from only two localities, both karst limestone areas, which are not in National Parks (hills in the Tham Lod Cave area, and cliffs surrounding the Wat Phra That Doi Tung Temple).
Other material examined. Thailand. Chiang Rai, Doi Tung, en route from Huai Krai to Wat Doi Tung, c.900 m, 24 ix 1967, K. Iwatsuki et al. 10951 (A, AAU, BKF, L); Chiang Rai, Doi Tung, upper catchment valley N of Doi Tung temple, c.1,300 m, 29 x 2005. C.-I Peng et al. 20658a & b (HAST); Mae Hong Son, Pang Ma Pha, Tham Lod Cave area, 657 m, 22 x 2014, D. J. Middleton et al. 5827 (BKF, E, SING).
Begonia pseudosubperfoliata Phutthai & M.Hughes sp. nov. Sect. Diploclinium. Figs 2 , 5 .
Resembles Begonia subperfoliata Parish ex Kurz in habit but differs in having 5 tepals in the female flowers (not 2) and glabrous lanceolate bracts (not deeply dissected and papillose). Also similar to Begonia rabilii Craib in habit but differs in having 5 tepals in the female flowers (not 4), and leaves with a more deeply crenate margin. – Type: Thailand, Chon Buri, Bo Thong District, Khao Cha Ang On cave. On limestone karst in deep shade, 350 m altitude, 10 ix 2007, T. Phutthai 162 (holo BKF; iso E, PSU).
Begonia pseudosubperfoliata Phutthai & M.Hughes. A, Habit and habitat of shaded karst limestone; B, inflorescence; C, male flowers; D, female flower; E, capsule (all photographs from Phutthai 162).
Monoecious herb, 5–15 cm tall. Stems tuberous, globose or subglobose, c.10 mm diam., with numerous fibrous roots. Leaves 1–(2 or 3) per plant; petiole dark red 2–7 cm long; leaf blade membranous, symmetrical, chartaceous when dry, peltate, petiole insertion 10 mm from the margin, 2–6 × 1–5 cm, base rounded, apex acute, margin crenate or undulate, venation palmate, veins 5 or 6, prominent beneath, adaxial surface dull dark green or bright light green, sparsely echinate, abaxial surface pale green, glabrous on both sides. Stipules caducous, lanceolate, c.2 mm long. Inflorescences arising from tuber, cymose, bisexual, 5–10 cm long, staminate flowers basal and pistillate flowers distal, protandrous; peduncles terete, dark red or pale green, glabrous, 4–8 cm long. Bracts persistent, lanceolate, c.2 × 1 mm. Staminate flowers: pedicels glabrous, c.10 mm; tepals 4, pink or pale pink, outer 2 obovate, 5 × 4 mm, base obtuse, apex obtuse, margin entire, glabrous on both sides, inner 2 oblanceolate, 3–4 × 1.5–2 mm, base obtuse, apex obtuse, margin entire, glabrous; androecium zygomorphic, stamens 8–12, filaments nearly free c.0.5 mm long, anthers oblong c.1 mm long, dehiscing by longitudinal slits. Pistillate flowers: pedicels 10–15 mm long, pale green, sparsely hairy or nearly glabrous; tepals 4, pink or pinkish white, outer 2 ovate or obovate, c.5 × 4 mm, glabrous, inner 2 oblanceolate, 3 × 1–2 mm, glabrous on both sides; styles 3, fused at base; stigmatic band crescent-shaped; ovary with 3 unequal wings, sparsely pubescent; 3-locular, placentation axillary, 1 branch per locule. Fruits dehiscent, drying pale brown, 10–13 × 10 mm including wings; capsule locules globular, c.5 × 4 mm, abaxial wing triangular, 5–8 mm long, 2 lateral wings narrower, narrowly rectangular, 4 mm long and curved along length of capsule.
Distribution
Endemic to Southeastern Thailand, Bo Thong District, Chon Buri Province.
Habitat and ecology
On karst limestone cliffs in shade, with water seepage at 350 m. Flowering July to September; fruiting September to November.
Notes
The specific epithet pseudosubperfoliata highlights the similarly of this species to Begonia subperfoliata.
Provisional IUCN category
Vulnerable VU D2. Endemic to a single locality, the karst cave of Khao Cha-ang. The status of the cave as a tourist attraction means it is less likely to be destroyed by mining, but disturbance through climbing and reduction in the quality of the local microclimate through vegetation clearance have the potential to affect this species adversely.
Acknowledgements
The authors would like to thank the curators and staff of the following herbaria: AAU, ABD, BK, BKF, BM, C, E, HAST, K, L, PSU and SING. The Royal Botanic Garden Edinburgh is supported by the Scottish Government's Rural and Environment Research and Analysis Directorate. We thank Mr Preecha Karaket (BKF) for his beautiful photographs; Ching-I Peng (HAST) for fieldwork supported by research grants from Academia Sinica, Taiwan, and photographs. This work was supported by the Newton Fund Researcher Links programme, part of the UK's official development assistance programme administered by the British Council.
