Borah, D., M. Taram & M. Hughes (2023). Begonia egamii (Begoniaceae), a remarkable new species from Arunachal Pradesh, India. Candollea 78: 147–151. In English, English abstract. DOI: http://dx.doi.org/10.15553/c2023v782a5
The new species Begonia egamii D. Borah, Taram & M. Hughes (Begoniaceae) is described based on collections made in Leparada District of Arunachal Pradesh, India. It is superficially similar to B. tamdaoensis C.I Peng in having hispid hairs on the tepals and ovary and a zygomorphic androecium, but differs in having leaves rugulose above (vs. smooth), two stigmas (vs. three), and anthers retuse at the apex (vs. with an extended connective).
Received on May 5, 2023. Accepted on October 5, 2023. First published online on November 20, 2023.
Introduction
Arunachal Pradesh, commonly referred to as “land of dawn lit mountains”, is the largest state of Northeast India, with a high forest cover of 80 % of its area (India State of Forest Report, 2021). Hosting a diversity of habitats and a rich flora, this state has been a paradise for botanists since the 18th century. Begonia L. currently has 2,117 species worldwide and the number is still growing each year due to new discoveries (Moonlight et al., 2018; Hughes et al., 2023). In the state of Arunachal Pradesh 49 species of Begonia are known, eight of which were recently described and six species recorded in the region for the first time (Taram et al., 2020, 2021, 2022, 2023; Borah et al., 2021a, b, c, d; Krishna et al., 2021; Wahlsteen & Borah, 2022). These species fall under four different sections following the sectional treatment of Moonlight et al. (2018).
In recent years, internet based image databases and social media have become an important tool for plant enthusiasts and botanists to share their interest and knowledge of species diversity and taxonomy leading to the discovery of new species (Gonella et al., 2015). Photographs of an interesting Begonia from Leparada District of Arunachal Pradesh were posted on facebook by Egam Basar, Director of State Horticulture, Research and Development Institute, Govt. of Arunachal Pradesh, India in December 2020. After contacting him, the authors of the present contribution collected a few specimens that are here recognized as a new species. It is described and illustrated below and named B. egamii after the discoverer.
Material and methods
Morphological observations and measurements of the species were made on both living material and dried specimens. Comparison was made with the protologues of Begonia species recorded from India and adjacent countries. Digital images of type specimens deposited at ASSAM, BM, CAL, E, G, K, L, P, and PE were examined.
Taxonomy
Begonia egamii D. Borah, Taram & M. Hughes, sp. nov. (Fig. 1, 2).
Holotypus: INDIA. Arunachal Pradesh: Leparada, Basar, EB Project Nature, 27 ′35″N 94′43″E, 1000 m, 4.I.2023, Taram & Borah 10023 (CAL!).
Begonia egamii D. Borah, Taram & M. Hughes has a very unusual combination of characters, making it hard to find a close ally for taxonomic comparison. It shares some characters with B. tamdaoensis C.I Peng such as having hispid hairs on the tepals and ovary and a zygomorphic androecium, but differs in having leaves rugulose above (vs. smooth), two stigmas (vs. three), and anthers retuse at the apex (vs. with an extended connective).
Creeping herb, 15 – 28 cm long, strigose; rhizome 5–10 × 1–1.5 cm, internodes very short at base, becoming a creeping stem toward apex with internodes 1–4 cm long, mixed with more congested internodes so leaves can appear crowded together, stipules triangular to elliptic-ovate, 1–1.6 × 0.8–1.2 cm, glabrous adaxially, pubescent abaxially, margin ciliate, apex shortly acuminate. Stem decumbent, 8–22 × 0.3–0.5 cm, rooting at nodes, indumentum strigose (trichomes c. 5 mm long), red. Leaves appearing clustered when internodes are close together, on 6–20 × 0.2–0.3 cm petioles; lamina elliptic-ovate, 8–30 × 6–18 cm, rugulose, apex acute to shortly acuminate, base cordate with lobes overlapping, margin subentire, crenate, or serrate, ciliate, densely strigose, veins palmate, 7–9. Inflorescence axillary, cymose; peduncles strigose, primary 7.3–20 cm long, secondary 1.3–7.5 cm long, tertiary 0.5–4.5 cm long; bracts lanceolate to elliptic-ovate, 0.5–1 × 0.3–0.6 cm, acute, entire, pubescent, with a pedicel 1–2 cm long. Staminate flower with 4 tepals; outer tepals 2, broadly ovate to orbicular, 1.3–2 × 1–1.5 cm, glabrous inside, pubescent outside, pink; inner tepals 2, ovate to elliptic ovate, 1–1.3 × 0.5–0.7 cm, glabrescent outside, glabrous inside, pinkish white; stamens 30–60, anthers basifixed, ellipticobovate, c. 2 mm long, connective retuse, filament c. 1.5 mm long, fused at base into a stout column; pedicel 2.5–4 cm long, strigose. Pistillate flower with 5 tepals, unequal, elliptic ovate to broadly ovate, 1–1.3 × 0.9–1.2 cm, strigose outside, glabrous inside, pink; pistil c. 2–3 mm long, styles 2, c. 1 mm long, persistent, stigma papillose, yellow, ovary 2-locular, placentae bifid; pedicel 1–2 cm long, strigose. Capsule 1.2–1.5 cm long, densely strigose, with 1 oblong central wing and 2 shorter obtuse lateral wings, central wing 1–2 × 0.8–1 cm, lateral wings 1–1.2 × 0.3–0.5 cm.
Etymology. – The species is named after Shri. Egam Basar, a dedicated plant grower who first discovered the species in Leparada District of Arunachal Pradesh, India.
Distribution, ecology and phenology. – Begonia egamii is known only from the type locality in the EB Project Nature reserve area, Arunachal Pradesh, northeastern India. This reserve area is spread over 100 hectares dedicated to safeguard the native and threatened plant species of Arunachal Pradesh. It was found growing in two different habitat types: (1) gregariously in a recently cleared patch fully exposed to sunlight along with Dicranopteris linearis (Burm. f.) Underw., Pteridium aquilinum (L.) Kuhn, Pseudodissochaeta assamica (C.B. Clarke) Nayar, Dimetia scandens (Roxb.) R.J. Wang, Carex sp.; (2) on moist shady cliff faces in association with Henckelia adenocalyx (Chatterjee) D.J. Middleton & Mich. Möller, Begonia handelii Irmsch., Hydrocotyle himalaica P.K. Mukh., Rhynchotechum parviflorum Blume, Boeica fulva C.B. Clarke, Alpinia sp., along with mosses and liverworts.
Flowers from November to December, fruiting from December to January.
Notes. – Although the pistillate flowers with two stigmas, two-locular ovaries with axile and bifid placentae conform well with Begonia sect. Platycentrum, the asymmetric androecium is unusual for the section (Fig. 2C). The elongate creeping habit is also unusual; the geographically closest species with the same habit is B. repenticaulis Irmsch. from Yunnan, which considerably differs from B. egamii in having acutely lobed leaves. The unusual combination of characters suggests that the species may represent an isolated lineage. For the time being, the sectional placement of the new species remains undefinied awaiting further research.
In combination with several other recent discoveries, this new species confirms the status of the montane forests of northeastern India as a region of immense floristic diversity and endemism. It also highlights the utility of baseline regional taxonomic revisions in supporting and stimulating further taxonomic work.
Fig. 1.
Begonia egamii D. Borah, Taram & M. Hughes. A. Habit; B. Adaxial leaf surface; C. Abaxial leaf surface; D. Stipule; E. Staminate flower (inner view); F. Staminate flower (outer view); G–H. Outer tepals of a staminate flower; I–J. Inner tepals of a staminate flower; K. Style; L. Pistillate flower; M. Fruit; N. Cross section of a fruit showing locules. [Photos: D. Borah & E. Basar]
Acknowledgements
We thank Ojar Taku for his travel assistance, Egam Basar and Tokar Angu for their help in the field and Edinburgh Botanic Garden (Sibbald) Trust, Project No: 2022#19 for the funding.
© CONSERVATOIRE ET JARDIN BOTANIQUES DE GENÈVE 2023
