Begonia naemma Y.P.Ang, Aumentado & Magtoto

Ang, Y. P., Aumentado, J. A. & Magtoto, L. M., 2022, Begonia Naemma (Sect. Petermannia, Begoniaceae), A New Species From Nueva Ecija, Luzon Island, The Philippines, Edinburgh Journal of Botany 79 (390), pp. 1-10 : 2-6

Begonia naemma Y.P.Ang, Aumentado & Magtoto , sp nov.

§ Petermannia .

Allied to Begonia polyclada C.I Peng, C.W.Lin & Rubite by having a branched and erect stem with an antrorsely tomentose vestiture and bearing numerous small leaves that are held horizontally. Additionally, both species produce inflorescences in the upper axils or terminally, with 2-tepaled staminate flowers and 5-tepaled pistillate flowers. However, the new species is distinct from Begonia polyclada by having larger leaves (20–45 × 6–19 mm vs 7–16 × 3.5–8 mm); leaf adaxially sparsely hirsute between the veins (vs glabrous); more numerous stamens (c.25 vs c.15); pistillate flower tepals elliptic to obovate (vs narrowly elliptic to ovate); and ovary wings ovate-oblong, rounded proximally and truncated distally (vs rounded triangular in shape) and comparatively larger (c.18 × 5–7 mm vs c.10 × 3.5–5.5 mm).

– Type: Philippines, Luzon, Nueva Ecija, Pantabangan–Carranglan Watershed Forest Reserve , elevation c. 1200 m a.s.l., 16°00′27.2′′N, 121°11′03.3′′E, 12 iii 2021, PTI-PCWFR1-0021 (holotype PNH [accession no. 258608 ]; isotypes CAHUP [accession no. 074230 ], PNH [accession no. 258609 ]). Figures 1 , 2 .

Monoecious herb, perennial c. 25 cm tall. Stem much branched, erect, olive to brown, c. 2 mm thick, antrorsely tomentose; internodes 7–15 mm long on upper axils. Stipules brown, persistent, narrowly triangular, c.3 × 1–1.5 mm, glabrous, chartaceous, margins entire, slightly keeled, apex cuspidate, cusp c. 1.5 mm long. Leaves numerous, alternate, distichous, held horizontally; petiole terete, olive green, 0.5–3 mm long, same texture as stems; lamina oblong-lanceolate-ovate, slightly asymmetrical, 20–45 × 6–19 mm; adaxially dark green, hyaline, sparsely hirsute between the veins; abaxially pale green, appressed puberulous on veins; base shallowly oblique; margins coarsely serrate, pointed on vein endings, apex acute; venation pinnate, midrib 20–45 mm long, lateral primary veins c.3 on each side, adaxially slightly sunken and abaxially slightly raised. Inflorescence protogynous, axillary on upper branches to terminal, typically held under the leaves, staminate flowers on 3–5 few-flowered monochasial cymes, borne on short lateral stems 2–6 mm long; pistillate flowers solitary and basal to staminate flowers; peduncle 3–11 mm long, pale green, same texture as stem. Bracts hyaline pale green, persistent, glabrous, narrowly triangular, lowest bract c.3 × c. 1.5 mm, margins entire, decreasing in size towards summit of inflorescence. Staminate flower pedicel 5–11 mm long, antrorsely puberulous, tepals 2, widely ovate to orbicular, 9–11 mm in diameter, hyaline white to pale pink near attachment, base shallowly cordate, apex rounded, margins entire, abaxially sparsely puberulous; androecium nearly actinomorphic, c. 4 mm in diameter; stamens yellow, c.25; filaments 0.8–1.2 mm long, slightly fused at base; anthers obovate, apex retuse, dehiscing along 2 arched slits that run along the length of the anther, c. 1 mm long. Pistillate flower pedicel c. 12 mm long; tepals 5, antrorsely puberulous, hyaline white to pale pink near apex, margins entire, elliptic to obovate, 9–11 × 5–6 mm, base cuneate, apex rounded to acute; ovary white with a pale pink band along the middle, trigonous-ellipsoid, c.11 × c. 5 mm (wings excluded), wings subequal, ovate-oblong, rounded proximally and truncated distally, c.18 × 5–7 mm, glabrous except sparsely hirsute at the wing margin, 3-locular, placentation axile; styles 3, yellow, bifid, c. 3 mm long; stigmas in a spiral band and papillose all around; ovate to oblong. Capsule not seen.

Etymology. The specific epithet, naemma , is the word in Ilocano that means ‘shy and humble’. This reflects the difficulty in noticing the species in situ due to its resemblance to other herbaceous plants such as Elatostema pilosum Merr. ( Merrill 1919: 376) , with which it was growing sympatrically. The species was discovered only by chance because it was flowering. Distribution and ecology. Begonia naemma is narrowly distributed and currently known only from its type locality in the PCWFR ( Figure 3 ). It is found growing on soil slopes or lithophytically at least 1200 m a.s.l., along with Elatostema Wight and Selaginella P.Beauv. species. It occurs in two localities: one at c. 1200 m a.s.l. and another at 1500 m a.s.l. Proposed IUCN conservation category. Begonia naemma has a restricted distribution and a relatively small number of mature individuals (only two localities [one location sensu IUCN] were observed with fewer than 100 mature plants per locality). It has an EOO and AOO of 4 km 2. Moreover, a potential threat of land conversion is noted, because economic crops are introduced in the lower slopes of the mountain. Presently, pockets of illegal logging have been observed in the area by locals, and this activity has shown no sign of stopping despite the locality being designated as a protected area. Because the survival of Begonia naemma is strongly tied to the overall health of the ecosystem, any forest disturbances are likely to affect this species negatively. Following the IUCN criterion B, Begonia naemma is hereby assessed as Critically Endangered CR B1ab(iii)+2ab(iii) ( IUCN Standards and Petitions Committee, 2019).

The dainty morphology of Begonia naemma , with its numerous small, horizontally held leaves, is seen in only one other Philippine Begonia species: B. polyclada . Such adaptation could potentially help the species avoid herbivory by blending in with the surrounding vegetation; in this case, looking like Elatostema pilosum by having a much-branched lignified habit, oblong leaves with few marginal teeth, narrowed to the base, acuminate-caudate leaf apex, antrorse pilose stem, and sessile inflorescence. As observed, Begonia naemma and Elatostema pilosum are growing sympatrically ( Figure 4 ).

The characters of Begonia naemma and B. polyclada are compared in the Table.

Figures

Figure 1. Begonia naemma Y.P.Ang, Aumentado & Magtoto, sp. nov. A, Habit; B, stipule; C and C′, leaf (adaxial and abaxial surface, respectively); D, bract; E and E′, staminate flower (face view and side view, respectively); F, stamen; G, pistillate flower (face view); H, pistillate flower (side view, showing ovary); I, ovary (cross-section). Drawn from the type collection (PTI-PCWFR1-0021) by Y. P. Ang.

Figure 2. Begonia naemma Y.P.Ang, Aumentado & Magtoto, sp. nov. A, Habitat and habit; B, stem vestiture and stipules; C and C′, leaf (adaxial and abaxial surface, respectively); D, immature staminate flower and bracts; E, pistillate flower (face view); F, pistillate flower (side view, showing ovary); G, ovary (cross-section). All photographs of the type collection (PTI-PCWFR1-0021), taken by M. N. Tamayo (A), R. A. A. Bustamante (B–F) and L. M. Magtoto (G).

Figure 3. Distribution map for Begonia naemma (star) and B. polyclada (triangle).

Figure 4. Sympatric relationship of Begonia naemma and Elatostema pilosum. A, Begonia naemma (top arrow) in situ, growing sympatrically with Elatostema pilosum (bottom arrow); B, E. pilosum (close-up). All photographs taken at the type locality by M. N. Tamayo.