Gardens’ Bulletin Singapore 73(2): 475–480. 2021 475 doi: 10.26492/gbs73(2).2021-17 Begonia arunachalensis (Begoniaceae), a new tuberous species of Begonia from Arunachal Pradesh, India D. Borah1, M. Taram2, L. Yama3 & E. Wahlsteen4 1 Department of Botany, Goalpara College, Goalpara – 783101, Assam, India dipankar.borah@goalparacollege.ac.in 2 Department of Botany, Rajiv Gandhi University, Rono Hills, Doimukh – 791112, Arunachal Pradesh, India 3 Centre for Bioresources and Sustainable Development, Department of Biotechnology, Kimin, Lower Subanisiri – 787031, Arunachal Pradesh, India 4 Botanical Museum, Lund University, PO Box 117, SE-22100 Lund, Sweden eric.wahlsteen@gmail.com ABSTRACT. A new species, Begonia arunachalensis D.Borah & Wahlsteen (Begoniaceae) is described and illustrated. It is distributed in Papum Pare District of Arunachal Pradesh where it grows near streams in rock crevices. Begonia arunachalensis is similar to B. brevicaulis A.DC. but differs in its pendent fruits, number of locules and capsule wings, and longer lateral wings. It belongs to Begonia sect. Diploclinium. Keywords. Eastern Himalaya, morphology, Papum Pare, taxonomy Introduction Begonia L. with over 2035 accepted species (Hughes et al., 2015–) is one of the largest plant genera in the world and one of two genera in the family Begoniaceae (Taram et al., 2020). However, the total diversity of the genus is still poorly understood due to the high degree of endemism, high diversity and lack of proper documentation in the most species rich areas of the world, such as the Himalayas, Kalimantan and New Guinea. Northeast India has a total of 41 species of Begonia in four different sections (Begonia sect. Diploclinium (Lindl.) A.DC., sect. Parvibegonia A.DC., sect. Platycentrum (Klotzsch) A.DC. and sect. Monophyllon A.DC.) (Camfield & Hughes, 2018; Krishna et al., 2021; Taram et al., 2020, 2021; Borah, 2021a,b). Begonia sect. Diploclinium includes about 85 species distributed in Bhutan, China, India, Laos, Malaysia, Myanmar, Nepal, Pakistan, Papua New Guinea, Sri Lanka, Taiwan, Thailand, Vietnam and West Papua. In northeast India about 10 species are present. The section is phylogenetically close to Begonia sect. Platycentrum and the former B. sect. Sphenanthera (Hassk.) Warb. and would form a monophyletic section if they were to be merged (Moonlight et al., 2018). However, such a treatment would result in a highly polymorphic section distinguished by no obvious morphological characters. The species of Begonia sect. Diploclinium are usually monoecious, tuberous and creeping. The inflorescence may be terminal or axillary with white or pink flowers, 476 Gard. Bull. Singapore 73(2) 2021 and pistillate flowers have 3-locular ovaries and usually 3 styles. It is similar to species in Begonia sect. Platycentrum but differs in its 3-locular ovary (vs 2), connective not extended (vs extended) and tuberous habit (vs rhizomatous). The authors collected several interesting specimens of Begonia spp. while conducting field trips in different districts of Arunachal Pradesh, Northeast India. One of them has recently been described as Begonia oyuniae Taram & N.Krishna (Taram et al., 2020) and others are in press. One such interesting tuberous specimen collected in Kimin, Papum Pare District was found to be a hitherto undescribed species. The taxonomic status was established after critical evaluation of relevant literature (Clarke, 1879; Gu et al., 2007; Camfield & Hughes, 2018) and type materials deposited in different herbaria (ASSAM, CAL, E, K and PE). Taxonomy Begonia arunachalensis D.Borah & Wahlsteen, sp. nov. Similar to Begonia brevicaulis A.DC. but can be distinguished by its pendent (vs recurved) fruit, number of locules 3–4 (vs 2), capsule wings 2–5 (vs 3) and lateral wings to 3 cm (vs 0.7 cm). From Begonia picta Sm. it differs in lateral wings to 3 cm (vs 1.2 cm), pistillate flower with 4 tepals (vs mostly 5) and c. 25 stamens (vs numerous). – TYPE: India, Arunachal Pradesh, Papum Pare District, Kimin, 210 m, 22 August 2019, D. Borah, M. Taram & L. Yama 5671 (holotype CAL; isotype CAL). (Fig. 1, 2) Plant monoecious, tuberous, perennial, 3–20 cm tall. Stem 4–17 cm long, 2–5 mm thick, internodes 0.7–9 cm long. Stipules translucent, green, ovate, 1.8–2.0 × c. 1 mm, pubescent, margin entire, apex cuspidate. Petiole whitish green, terete, 0.5–10.5 cm long, 1–3 mm thick, pubescent, hairs white. Blade green, broadly ovate to orbicular, 4–11 × 3.5–10 cm, asymmetric, densely hairy on both surfaces; venation palmate, 7–9 veined; slightly cordate at base, lobes not overlapping, margin irregularly dentate, apex acuminate. Inflorescence axillary, 2.5–15 cm long, 1–3 branched, peduncles reddish green, densely pubescent, 1–3 mm in diam.; bracts ovate, 1.8–2 × 0.8–1 mm, pubescent on both sides, margin entire. Flowers 2–10 per inflorescence. Staminate flower: pedicel light green to reddish green, pubescent, flowers 1–3 cm in diam.; tepals 4; outer 2 larger, ovate, 8–11 mm long, pubescent outside, glabrous inside, whitish pink; inner 2 smaller, obovate, 4–7 mm long, glabrous, white; androecium 3–5 mm long, 1–2 mm wide, stamens 25+, filaments 1–2 mm long, anthers yellow, ovate, 0.8–1 mm, apex rounded. Pistillate flower: pedicel pink, pubescent, 2–4.5 cm long; flowers 0.8–1 cm in diam.; tepals (3–)4, pinkish white, pubescent outside, glabrous inside; outer 2 broadly ovate to round, 4–6 mm long; inner tepals broadly obovate, 2.5–5 mm long; styles fused, 1–3 mm long; stigma 3–4, yellow; ovary 4–5 mm long, pinkish green, densely pubescent, 2–5 winged. Capsule 0.7–1.1 cm long, pendent, lateral wings up to 3 cm; locules 3–4. Begonia arunachalensis, a new species from India 477 Fig. 1. Begonia arunachalensis D.Borah & Wahlsteen. A. Habitat. B. Habit. All photographed near Kimin, Papum Pare disctrict, Arunachal Pradesh. (Photos: D. Borah) Distribution, habitat and phenology. The new species is endemic to Arunachal Pradesh. It grows near streams, waterfalls, and moist shaded areas at about 200 meters above sea level in rock crevices by the roadside. It is associated with Henckelia hookeri (C.B.Clarke) D.J.Middleton & Mich.Möller, Globba multiflora Wall., Elatostema sp., Rhynchotechum ellipticum (Wall. ex D.Dietr.) A.DC., Monolophus coenobialis Hance, etc. Begonia arunachalensis flowers and fruits from August to September. Etymology. The specific epithet refers to the state of Arunachal Pradesh, where the species was discovered. Provisional IUCN conservation assessment. Least Concern (IUCN Standards and Petitions Committee, 2019). Approximately 2000 individuals were found in several scattered locations in Kimin, Lower Subansiri District of Arunachal Pradesh over a range of 10 km. Notes. Begonia arunachalensis belongs to Begonia sect. Diploclinium which is characterised by its tuberous habit, three locules and two placental branches per locule. Although Begonia brevicaulis is rather similar to the new species, it belongs 478 Gard. Bull. Singapore 73(2) 2021 Fig. 2. Begonia arunachalensis D.Borah & Wahlsteen. A. Tuber. B. Leaf adaxial surface. C. Leaf abaxial surface. D, E. Inflorescence. F. Buds showing pubescence. G. Male flower. H. Female flower. I–K. Fruit. (Photos: D. Borah) Begonia arunachalensis, a new species from India 479 to Begonia sect. Parvibegonia with two locules and terminal inflorescences and is found in Meghalaya. Begonia picta is in the same section as the new species, and is also found in Arunachal Pradesh, but is easy to identify by its variegated leaves. The new finding adds to the species richness of Arunachal Pradesh and shows that ongoing botanical surveys of the area are essential for a better understanding of the species composition and ecology of the state. Identification key to the species of Begonia sect. Diploclinium in Arunachal Pradesh 1a. Leaves peltate ........................................................................................ B. josephi 1b. Leaves basifixed .................................................................................................. 2 2a. Plants rhizomatous ............................................................................ B. scintillans 2b. Plants tuberous ..................................................................................................... 3 3a. Plant caulescent, stem upright, inflorescences born on the main stem ................... ....................................................................................................... B. pedunculosa 3b. Plant acaulescent, inflorescences born directly from tuber .................................. 4 4a. Plant dioecious; capsule wings equal; petiole short (1–5 cm) ................. B. dioica 4b. Plant monecious; capsule wings unequal; petiole long (3–16 cm) ...................... 5 5a. Tepals glabrous, small (2–7 mm long) ............................................... B. ovatifolia 5b. Tepals hairy, long (5–21 mm long) ...................................................................... 6 6a. Number of stamens 8–10; tepals 5–10 mm long ................................. B. labordei 6b. Number of stamens 16–100; tepals 8–21 mm long ............................................. 7 7a. Leaves often variegated; tepals serrate, female tepals 5 ........................... B. picta 7b. Leaves plain green; tepals entire, female tepals 4 ..................... B. arunachalensis ACKNOWLEDGEMENTS. We are thankful to Rajiv Gandhi University and Goalpara College for providing necessary facilities for conducting the work. We are thankful to Dr Mark Hughes of the Royal Botanic gardens, Edinburgh for his comments on the novelty. We also extend our sincere gratitude towards Mr Roopan Likha, Miss Timba Mepi and Mr Milan Bharali for their work on the field trips. 480 Gard. Bull. Singapore 73(2) 2021 References Borah, D., Taram, M. & Wahlsteen, E. (2021a). Begonia dicressine (Begoniaceae): a new record for India. Nat. Conservation Res. 6(4): 1–2. Borah, D., Taram, M. & Wahlsteen, E. (2021b). Begonia limprichtii Irmsch. (Begoniaceae) – a new record for India. Biodivers. Res. Conservation 61: 29–33. Camfield, R. & Hughes, M. (2018). A revision and one new species of Begonia L. (Begoniaceae, Cucurbitales) in Northeast India. Eur. J. Taxon. 396: 1–116. Clarke, C.B. (1879). Begoniaceae. In: Hooker, J.D. (ed.) Flora of British India, vol 2, pp. 636–656. London: L. Reeve & Co. Gu, C., Peng, C.I & Turland, N.J. (2007). Begoniaceae. In: Wu, Z. & Raven, P. (eds) Flora of China, vol. 13, pp. 153–207. Beijing: Science Press; and St Louis: Missouri Botanic Garden Press. Hughes, M., Moonlight, P.W., Jara, A. & Pullan, M. (2015–). Begonia Resource Centre. http:// padme.rbge.org.uk/begonia/. Accessed 31 Aug. 2021. IUCN Standards and Petitions Committee (2019). Guidelines for Using the IUCN Red List Categories and Criteria. Version 14. Prepared by the Standards and Petitions Committee. Available from http://iucnredlist.org/documents/RedListGuidelines.pdf. Krishna, N., Pradeep, A.K., Amrutha, A. & Jayakrishnan, T. (2021). A new species and a new record of Begonia (sect. Platycentrum, Begoniaceae) from northeastern India. Phytotaxa 482(3): 261–267. Moonlight, P.W., Ardi, W.H., Padilla, L.A., Chung, K.F., Fuller, D., Girmansyah, D., Hollands, R., Jara-Muñoz, A., Kiew, R., Leong, W.-C. et al. (2018). Dividing and conquering the fastest-growing genus: towards a natural sectional classification of the mega-diverse genus Begonia (Begoniaceae). Taxon 67(2): 267–323. Taram, M., Borah, D., Krishna, N., Pradeep, A.K., Amrutha, A. & Hughes, M. (2020). Begonia oyuniae (Begonia sect. Monophyllon, Begoniaceae), a remarkable new species from Northeast India. Gard. Bull. Singapore 72: 109–115. Taram, M., Borah, D. & Hughes, M. (2021). Begonia kekarmonyingensis (Begoniaceae), a new species from Arunachal Pradesh, Northeast India. Phytotaxa 494(3): 268–272.