Begonia (sect. Sphenanthera) silletensis C. B. Clarke 1879
Creators: name: Camfield, Rebecca
name: Hughes, Mark
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Cucurbitales
Begoniaceae
Begonia
Begonia silletensis

description: Begonia silletensis (A.DC.) C.B.Clarke [sect. Sphenanthera]
Fig. 58
The Flora of British India 2: 636 (Clarke 1879). – Casparya silletensis A.DC., Prodromus Systematis Naturalis Regni Vegetabilis 15 (1): 277 (de Candolle 1864).
– Type: India, Meghalaya, Sillet Hills, Wallich Cat. No. 9107 (lecto-: K-W, barcode K000634631, here designated; isolecto-: BM000017324, G-DC, K-W, barcode K000634630).
Citations in other publications
As B. silletensis: Clarke (1881: 115), Chauhan (1996: 176), Tebbitt & Guan (2002: 134), Uddin (2007: 595), Hughes (2008: 116), Khatun (2008: 13), Dash (2010: 40), Dash & Mao (2011: 2095), Morris (2012b: 146); as Casparya silletensis: Baruah & Choudbury (2014: 41).
Other material
INDIA: Arunachal-Pradesh: Amjee, Sastry 40556 (ARUN n.v.); Bapu Mountain, Rotung, 24 Nov. 1911, Burkill 37376 (CAL n.v.); ibid., Nov. 1911 – Mar. 1912, Burkill 36700 (K); Buyang, Dash 32695 (ARUN n.v.); Kameng District, 24 Mar. 1957, Panigrahi 6029 (CAL n.v.); Mishmi Hills, Kamlang Valley, Glo, 22 Mar. 1949, Ward 18439 (BM); Sangram to Koloring, Dash 31223 (ARUN n.v.). Assam: Cachar, Oct. 1873, Keenan s.n. (K); Cachar, Katakhal Forest, Mar. 1888, Mann s.n. (K); Charduar Forest, Apr. 1887, Mann s.n. (K); ibid., Apr. 1887, Mann s.n. (K); Namchung, 18 Apr. 1885, Clarke 37937A (K). Manipur: Watt 6875 (E).
Description
Rhizomatous, stemless, monoecious herb, 40–60 cm high. Rhizome: 8–10 mm wide, glabrous. Stipules: lanceolate, 10–20 × 4 mm, puberulent hairs on reverse, persistent. Leaves: petiole 10 – 60 cm long, short red tomentose or pubescent; lamina ovate to broadly ovate, basifixed, base cordate with lobes not overlapping, 10–33 × 8.5–21 cm, asymmetric, upper surface green, very sparsely puberulous all over or on veins mostly near petiole attachment or glabrous, underside green, red puberulous all over, denser on veins, venation palmate, midrib 7–23 cm long; margin entire or with small teeth at ends of main veins, with sparse short hairs; apex short acuminate or acute. Inflorescence: cymose, terminal, few; peduncle with puberulous hairs, branching once; male primary 12 –25 cm long, secondary 1–2 mm long, 6–8 flowers; female primary 5–15 cm long, secondary 0.5(–4) cm long, 1–4 flowers; bracts ovate, 11–35 × 2–35 mm, margin entire, deciduous. Male flower: pedicel 1–4 cm long, red puberulous; tepals 4; outer tepals obovate, 4–20 × 10–15 mm, white to pink, red puberulous on reverse denser near base, margin entire; inner tepals spathulate, 13–17 × 7–12 mm, white to pink, glabrous; androecium with 70–100 stamens, symmetric; filaments 1–3 mm long, unequal, slightly fused at base or free; anther oblong elliptic, 1–2 mm long, dehiscing through slits running nearly the entire length of the anther, not hooded, connective extended. Female flower: pedicel 2–5 cm long, red puberulous hairs; bracteoles absent; tepals 4, equal obovate-orbicular, ca 16 × 15 mm, white to pink, puberulous on reverse denser near base, inner tepals similar yet smaller; ovary 3–4-locular, placentae bifid; capsule globose, densely red tomentose, without wings; styles 3–4, convoluted with twisted ends, caduceus. Fruit: upright, globose; capsule spherical, 8–23 × 10–15 mm, sparsely red tomentose to glabrous.
Distribution and phenology
Arunachal-Pradesh, Assam and Manipur; also in China, Bangladesh and Myanmar; 450–1000 m. Flowering: April to September; fruiting: April to October.
Conservation status
Least Concern. Begonia silletensis has an AOO of 44 km 2 and an EOO of 87,700 km 2 suggesting the species could be Vulnerable. There is, however, suitable habitat available in Northeast India, particularly the mountains of Arunachal-Pradesh and down into the Arakan mountain range. The species has been recorded near the Namphada Reserve and the Pakke Tiger Reserve.
Remarks
There has been much confusion over the delimitation of this species and how it can be separated from its nearest relative, B. aborensis, by using hair characters. Begonia silletensis is described as being glabrous (Tebbitt & Guan 2002; Dash & Mao 2011; Morris 2011c, 2012b), however, close examination of specimens cited in Tebbitt & Guan (2002) reveal some with short sparse pubescence, and one (Mann s.n.) with 5 mm long hairs we consider to belong to B. aborensis. After consulting all available specimens including two sheets of type material and the Kew specimen (K000634631) designated as the lectotype, it is clear that B. silletensis has soft short tomentose hairs along the veins on the lamina underside and petiole. The upper surface of the leaf looks glabrous at a glance, but with a hand lens or microscope small, sparsely spread hairs are often visible especially near the petiole attachment and along the veins. The same short tomentose pubescence is also found on the young ovaries but lost as the fruit ripens. The most reliable character for separating the two species is the longer peduncle in B. silletensis, and the longer, red indumentum on B. aborensis. In this account it has been decided to leave them as separate but very closely related species. Further studies on good flowering material and possibly a genetic analysis would be useful to give insight into whether they could be considered as a single, variable taxon. The plant photographed in Morris (2011c) identified as B. aborensis is referable to our concept of B. silletensis considering its very short indumentum and distinct peduncle.
Morris (2012b) shows photographs of a very large glabrous Begonia from Arunachal-Pradesh, referred to as B. silletensis. The plant has 5-locular fruit and flowers with 5–6 styles, and very large solitary female flowers over 10 cm diameter with up to 10 fringed tepals. This differs considerably from the type of B. silletensis and raises the possibility that the plant in the photograph is a new species.
There is variety of this species, B. silletensis var. mengyangensis Tebbitt & K.Y.Guan (Tebbitt & Guan 2002), found in Yunnan, China.All specimens viewed for this account are of the type variety B. silletensis var. silletensis.
description: Published as part of Camfield, Rebecca & Hughes, Mark, 2018, A revision and one new species of Begonia L. (Begoniaceae, Cucurbitales) in Northeast India, pp. 1-116 in European Journal of Taxonomy 396 on pages 91-93, DOI: 10.5852/ejt.2018.396, http://zenodo.org/record/3787049