Begonia hemicardia Elmer ex Rubite, 2022

Rubite, R. R., Ubaldo, D. B. H., Salcedo, J. C., Chung, K. - F., Evangelista, L. T., Tandang, D. N. & Hughes, M., 2022, BEGONIA HEMICARDIA (SECT. PETERMANNIA, BEGONIACEAE), A RESURRECTED HETEROTYPIC SYNONYM AND NOMEN NUDUM, Edinburgh Journal of Botany 79 (403), pp. 1-7 : 2-5

Begonia hemicardia Elmer ex Rubite , sp. nov.

Begonia hemicardia Elmer , in sched.; Merrill, Enum. Philipp. Fl. Pl. 3: 120 (1923), nom. nud. Begonia hemicardia is easily recognised by its combination of long internodes, large perSiStent StipuleS, Serrate leaf marginS, and long infloreScence on which Staminate flowerS are borne on a jointed rachiS. It iS Similar to Begonia megacarpa Merr. in its habit, large broad ovate leaveS, and pink and white flowerS but iS diStinguiShed by having lanceolate stipules (vs ovate to oblong-ovate), leaf base obliquely cordate (vs broadly truncate or subcordate-truncate), leaf apex attenuate (vs acuminate), shorter petioles 2–4 cm (vs up to 8 cm), smaller leaves 4–8.5 × 2.5–7 cm (vs 8–15 × 8–15 cm), separate male and female infloreScenceS (vS male and female flowerS in the Same infloreScence), male infloreScence pedunculate 1.5–2.5 cm (vS faScicled), and Smaller capSuleS 1.2–1.6 × 1.2–1.6 cm (vs 3 × 2 cm).

– Type: Philippines, Luzon, Sorsogon Province, Municipality of BuluSan , BuluSan Volcano Natural Park , elevation 350 m, 12°45′02′′N, 124°05′41′′E, 24 v 2006, R. Rubite, Luisito T. Evangelista, Chien-I Huang and Tsui-Ya Liu 297 (holotype PNH [ PNH258565 ]; isotypes HAST [ HAST115385 , HAST115386 ], PNH [ PNH258566 ]). Figures 1 , 2 .

Plant entirely glabrous, monoecious, perennial. Stem scandent 3–4 m long and 4–7 mm in diameter, internodes 6–8 cm long, rooting at the nodes. Stipules pale green, hyaline, lanceolate, 22–25 × 7–8 mm, glabrous, slightly keeled, margin entire, apex acuminate; persistent. Leaves alternate; petioles succulent, green becoming reddish green when mature, 20–40 × 1 mm; blade asymmetrical, obliquely, broad ovate, 4–8.5 × 2.5–7 cm, margin serrate or dentate and shallowly undulate; base obliquely cordate, apex attenuate; primary veins 6 or 7, grooved. Inflorescences: Separate male and female infloreScenceS ariSe in the uppermoSt leaf axilS or oppoSite a leaf; male infloreScence 8–9 cm long, cymoSe with c.5 × dichotomouS branching, becoming rachiS-like aS lower flowerS and pedicelS dehiSce; female infloreScence bearing 1 or 2 pairS of piStillate flowerS on a 1.5–2.5 cm long peduncle. Staminate flower: bracteoles boat-shaped, 4–6 × 5–8 mm, pink, pedicel 6–8 mm long, tepalS 2, orbicular, 7–10 × 8–12 mm, pink with white baSe; StamenS 25–30, filamentS 1 mm long shortly united at the base; anthers yellow, oblong 2 mm long. Pistillate flower: pedicel 10–14 mm long; tepals 5, pinkish white, margin entire, elliptic, 7–13 × 3–5 mm; ovary trigonous-ellipsoid, 8–10 × 6–8 mm (wings excluded), pink to brownish pink, 3-locular, placentation axile; 3-winged, wings equal, round, c.10 × 2–3 mm; styles 3, yellow, c. 3 mm long; stigmas in a spiral band. Capsule obovoid to turbinate, brown 12–16 × 12–16 mm; pedicel 14–18 mm long; wings 3, equal, rounded 12–16 × 2–4 mm.

Distribution and ecology. Endemic to Mount Bulusan, Sorsogon Province, Luzon, Philippines. Observed climbing on old Cyathea Sm. , and scrambling over boulders, at an elevation of 350 m.

Etymology. The epithet hemicardia is derived from the Greek hemi (‘half’ or ‘partial’) and cardia (‘heart’). It refers to the heart-shaped leaf base of the species.

Proposed IUCN conservation category. Begonia hemicardia is currently known only from the Bulusan Volcano Natural Park. In 2006, several populations were found along the forested road towards and inside the Park. During our expedition in 2017, only two populations were located. The Park is a popular tourist destination, thus roadsides are regularly cleared and planted with ornamental plants. Therefore, based on the IUCN Red List categories and criteria (IUCN Standards and Petitions Subcommittee, 2019), Begonia hemicardia is hereby proposed as Endangered (EN C1) due to this observed decline.

Additional specimens examined. PHILIPPINES. Luzon: Sorsogon, Mt Bulusan, x 1915, A.D. E. Elmer 14366 ( B, BM [2], K, L, P, U) ; ibid., xi 1916, A.D. E. Elmer 15262 ( B, BM [2], K, L, P, U) ; ibid., v 1916 A.D. E. Elmer 16083 ( B, BM [2], K, L, P, U) ; Sorsogon Province, Municipality of Bulusan, Bulusan Volcano Natural Park , 24 iv 2006, R. Rubite 297 ( PNH) ; ibid., 30 xi 2017, R. Rubite with J. Salcedo and D. Ubaldo 982 ( PNH) .

Begonia hemicardia is allied to a group of climbing species of Begonia from the Philippines that can be recogniSed by their axillary infloreScenceS, 2-tepaled Staminate flowerS, and numerous asymmetrical to subsymmetrical leaves, for example B. aequata A.Gray , B. binuangensis Merr. , B. edanoii Merr. , B. gracilipes Merr. , B. lagunensis Elmer , B. megacarpa Merr. , B. sarmentosa L.B.Sm. & Wassh. and B. wenzelii Merr. The new species, however, can be distinguished from the allied species by its long internodes, large persistent stipules, Serrate or dentate leaf marginS, and long infloreScence on which Staminate flowerS are borne on a jointed rachiS.

The features distinguishing Begonia hemicardia from allied species are summarised in the Table. We chose a contemporary collection rather than one of Elmer’s specimens as the type, because it matches the description morphologically, is associated with a georeferenced locality, and will be more feasible for generating DNA barcode data.

Figures

Figure 1. Begonia hemicardia Elmer ex. Rubite, sp. nov. A, Habit with female flowerS; B, Stem and Stipule; C, branching pattern; D, Staminate flower bud; E and F, male flower (front and Side viewS, respectively); G, fruit. Drawn by D. N. Tandang from R. Rubite 297.

Figure 2. Begonia hemicardia Elmer ex. Rubite, sp. nov. A, Climbing habit; B, Stipule, C, male flower; D, ripe fruit; E, male infloreScence with moSt flowerS dehiSced. A and E: photographS of R. Rubite 297, taken by Chien-I Huang. B–D: photographs of R. Rubite 982, taken by Cecil H. Ubaldo.