Begonia ahooensis P.L.Sherpa, Aditya Pradhan & Arun Chettri, 2021

Sherpa, Phurba Lhamu, Pradhan, Aditya, Chettri, Arun, Agrawala, D. K. & Biate, David L., 2021, A new species of Begonia (Sect. Diploclinium, Begoniaceae) from Sikkim, India, Phytotaxa 502 (3), pp. 289-294 : 289-291

Begonia ahooensis P.L.Sherpa, Aditya Pradhan & Arun Chettri sp. nov. § Diploclinium ( Figs. 1–2 )

Diagnosis: — Begonia ahooensis is similar to Begonia grandis but differs in the following characteristics: leaf margin entire, undulate (not irregularly serrulate); male-flowers with outer tepals sparsely pilose on reverse (not glabrous); female flowers with 5(3+2) tepals (not 3) and outer tepals pilose on reverse (not glabrous); stamens 11–44 (vs. 28–140); ovary hairy (not glabrous) with many distinct red dots and (not uniform pink or green) ( Table 1).

Type:— INDIA. Sikkim, East District, Ahoo-Yangtam , 895m, 27° 16’ 15.4” N, 88° 35’ 64.6” E. 15 th September 2016, P. L . Sherpa & Arun Chettri 00120 (holotype: BSHC00023659 ), 00120A-D (isotypes: BSHC00023660 , BSHC00023661 , BSHC00023662 , BSHC00023663 ) .

Description:—Perennial tuberous herb; up to 45 cm tall; tuber subglobose. Stem erect, cylindrical, solid, sparsely villose. Stipules caducous, ovate, 0.4–0.5 × 0.3–0.4 cm, membranous, glabrous. Leaves 4–8, simple, 10.4–19.4 × 12.2–14.3 cm; petiole 10.9–25 cm, densely to sparsely villose; lamina ovate, base obliquely cordate, asymmetrical, upper surface green, sparsely hirsute, underside pale green, sparsely villose, mostly on veins; margin entire and undulate, apex acuminate. Inflorescence cymose, axillary, pink; peduncle 0.7–9.6 cm; bracts ovate, 0.4–1.2 × 0.2–0.5 cm, pink pilose. Male flowers: pedicel 0.7–2.2 cm long, 10–19 per plant; tepals 4 (2+2); outer tepals ovate, 0.9–1.4 × 1.2–1.4 cm, larger than inner ones, sparsely pilose on reverse, inner tepals obovate, 1–1.2 × 0.4–0.8 cm, glabrous; androecium with 11–44 stamens, filaments 2–3 mm long, shortly monoadelphous; anther obovoid, 2–4 mm, yellow, basifixed. Female flowers: pedicel 0.2–2 cm long, 4–5 per plant; tepals 5 (3+2); outer tepals ovate, larger than inner ones, 1.3–2.4 × 1.1–1.3 cm, pilose on reverse; inner tepals ovate, 1.1–2 × 1.5– 1 cm, glabrous; ovary 3–locular, inferior 1–2.6 × 0.7–1.5 cm, styles 3, 4– 6 mm long, yellow in colour, deeply forked and twisted once; placentation axile, ovules many per locule. Fruit: capsule large, 1.1–2.4 × 1.6–3.9 cm including wings, pendulous with red dots, silvery white pilose; wings unequal, one ascending wing 1–3 cm long, two lateral wings 0.5–1.8 cm long, dehiscing through longitudinal slits. Seeds 220 × 190 µm, obovoidal, operculum small, elongated collar cells with striated-undulated anticlinal walls, polygonal testa cells with more or less undulated walls.

Phenology:—Flowering and fruiting during September – October.

Etymology:—The specific epithet refers to the name of the type locality.

Ecology:—Sub-tropical, mixed forest, grows along with other Begonia species such as Begonia megaptera A.DC. , Begonia roxburghii A.DC. , and Begonia picta Sm. Prefers moist shady habitat.

Distribution:—Endemic to the Ahoo area of East Sikkim, India ( Fig. 3 ).

Conservation Status:—The Area of Occupancy (AOO) can be estimated as 4 km 2 (Criteria B2) by taking the minimum grid size of 2 × 2 km 2 ( Fig. 1 ). The species is under threat from urbanization and road widening that has affected the quality of its habitat. The species is so far known from only one population/location and is exposed to a continuous decline in area and quality of habitat [Criterion Bab (iii)] and population size estimated to be fewer than 50 mature individuals in number (Criterion D). Therefore, after considering the threats mentioned above, and as per the IUCN (2019) guidelines, the threat perspective of this species can be assessed as ‘Critically Endangered’ [CR B2ab (iii) D].

Figures

FIGURE 1. Begonia ahooensis P.L.Sherpa, Aditya Pradhan & Arun Chettri: A. Habitat; B. Habit; C. Stipule; D. Inflorescence; E. Bract; F. Male flower; G. Female flower; H. Stamens; I. Stigma & Style; J. Transverse section of ovary. Scale 1–100 (e,f,h,i,j) = 16.5mm.

FIGURE 2. Begonia ahooensis P.L.Sherpa, Aditya Pradhan & Arun Chettri, SEM image of seed.

FIGURE 3. Distribution of Begonia ahooensis in Sikkim, India.