Begonia tiradpassensis Calaramo, Rubite, & C.W.Lin, 2023

Calaramo, Michael Agbayani, Rubite, Rosario Rivera & Lin, Che-Wei, 2023, Two new endemic Begonia species named after historical landmarks of Ilocos Sur, Philippines, Phytotaxa 613 (2), pp. 171-179 : 172-175

Begonia tiradpassensis Calaramo, Rubite, & C.W.Lin , sp. nov.

§ Baryandra ( Figs. 1 & 2 )

Type: — PHILIPPINES. Luzon: Ilocos Sur Province, Suyo-Cervantes, Amburayan River headwaters, on semi-shaded, wet, mossy rocks nearby a small waterfall in a cascading tributary along the river, ca. 1,300 m elevation, 28 June 2017, Calaramo 18051 (holotype PNH) .

Diagnosis: — Begonia tiradpassensis is closest to B. trichochila Warb. in having petioles covered with brownish hairs, leaves thick and slightly folded, staminate flowers with 4 tepals and an actinomorphic androecium. However, it is distinct from B. trichochila in having young leaves densely velutinous on the upper surface (vs. glabrous), sometimes with slightly raised venation (vs. flat), stamens 24–30 (vs. 50–60), pistillate flowers with 5 tepals (vs. 4 tepals), and a smaller capsule 15–18 × 11–15 mm (vs. 20–22 × 18–20 mm). Geographically, B. tiradpassensis is endemic to Ilocos Sur in northwestern Luzon, while B. trichochila occurs in Rizal, 250 km south of Ilocos Sur. It also resembles B. tandangii C.-I Peng & Rubite in vegetative characters and ovoid capsules with an acute apex, but differs in having brownish velutinous petioles (vs. glabrous or very sparsely puberulous), larger leaves 15–23 × 8–11 cm (vs. 8.4–12.5 × 6.8–10.5 cm), sparsely brown velutinous (vs. glabrous) on the adaxial lamina and peduncle, and caducous pistillate tepals (vs. sometimes persistent when fruiting).

Monoecious perennial rhizomatous herbs. Rhizome creeping, greenish-brown, 10–13 cm long, 15−20 mm thick, densely velutinous, hairs 6–8 mm long, internodes 8–11 mm long. Stipules ovate, pink to pale green, 20–33 × 16– 23 mm, herbaceous, keeled, margin entire, adaxially brownish velutinous, apex aristate. Leaves alternate; petiole terete, cream, 6−20 cm long, 3.5−5 mm thick; young leaves densely velutinous with 8–10 mm long hairs (pinkish when young becoming brownish when mature); blade asymmetric, obliquely ovate, 15–23 × 8–11 cm, basal lobes rounded overlapping, adaxial lamina olivaceous green, slightly folding (adaxially in-curved), with few remaining velutinous brown hairs in matured leaves; abaxial lamina pale green to cream, sparsely villous, more densely so on primary veins and petiole apex, margin subentire and shallowly lobed, undulate, apex acute; venation palmate, 6–8 primary veins, midrib distinguishable, secondary veins ca. 3 on each side, sometimes all venation slightly raised on upper surface, major and secondary veins prominent on lower surface, tertiary veins reticulate. Inflorescence axillary, bisexual, dichasial cymes branched 2 or 3 times; peduncle 15–20 cm long, cream to pale brown, basal parts covered with brownish villous hairs. Bracts widely ovate to elliptic, 4–6 × 3–4.5 mm, entire, adaxial surface light red to pink, subglabrous or with a few brown velutinous hairs. Staminate flower: pedicel pink to white, 15–20 mm long with sparse velutinous hairs 1–2 mm long; tepals 2+2, white to light pink, glabrous, outer pair ovate to suborbicular, 8–15 × 8–13 mm, apex rounded, inner pair oblanceolate to obovate, 9–12 × 3–6 mm, conduplicate with retuse apex; androecium actinomorphic, 6–8 mm across; stamens yellow, 24–30, filaments ca. 1.5 mm long, fused at base; anthers obovate, ca. 1 mm long. Pistillate flower: pedicel pink to white, 15–20 mm long with sparse velutinous hairs 1–2 mm long; tepals 2+3, white to light pink, glabrous, outer pair ovate to widely obovate, 8–15 × 7–10 mm, apex rounded, inner 3 obovate to narrowly obovate, 10–12 × 5–9 mm, apex slightly retuse to rounded; ovary pale green to pale pinkish-green, trigonous-ellipsoid, 7–9 × 3–4 mm (wings excluded), glabrous; wings 3, unequal, ca. 8 mm long, lateral wings very narrowly lunate, 2–4 mm wide; abaxial wing narrowly lunate, 3–5 mm wide, base cuneate; ovary 3-locular, placenta bilamellate; styles 3, pale yellowish-green to bright yellow, ca. 4 mm long, stigma spirally twisted. Capsule pendent, pedicel 15–20 mm long, ovary narrowly ovoid to trigonous-ellipsoid, 10–15 × 5–7 mm (wings excluded), light green when fresh; wings unequal, 15–18 mm long; lateral wings 3–4 mm wide, abaxial wing slightly larger at 6 mm wide.

Distribution and habitat: — Begonia tiradpassensis thrives on mossy rocks along a small ravine inside the Bessang Pass Natural Monument/Landmark at about 1,300 elevation on the southern ridge near the headwaters of Amburayan River that pass through the adjacent Tirad Pass Protected Area. Initially a small population was discovered with a few sporadic plants at the foot of Bessang Pass, but later a few plants were also found in Tiradpass Protected Area where more vigorous plants were documented. The small populations of B. tiradpassesensis occur in the said two protected areas in a sporadic manner. As of the last monitoring of the biodiversity research team, there are no other populations found outside this range.

Phenology: —Flowering between August to September.

Etymology: —Named after the historical site of the battle of Tirad Pass in Ilocos Sur, Philippines.

Conservation status: — Begonia tiradpassensis is currently known only from a small tributary along theAmburayan River in Ilocos Sur less than 500 km 2 in area. The entire population consists of about 200 to 250 including small individuals but fluctuates down to less than 200 matured plants. It is also frequently affected by annual landslides and erosion. Following IUCN Red List Categories and Criteria and Guidelines ( IUCN Standards and Petitions Committee, 2022), the species is provisionally assessed as being Endangered under the criteria (EN A2a; B2ab(iii,iv)).

Specimen examined (paratype):— PHILIPPINES. Luzon: Ilocos Sur Province, Suyo-Cervantes, Amburayan River , on semi-shaded, wet, mossy rocks nearby a small waterfall in a cascading tributary along the river, ca. 1,300 m elevation, 28 June 2017, Calaramo 18052 ( HNUL) .

Figures

FIGURE 1. Begonia tiradpassensis Calaramo, Rubite, & C.W. Lin. A, Habit; B, B’, Portion of leaf, adaxial and abaxial surface; C, Stipule; D, D’, Bracts; E, Staminate flower adaxial and lateral view; F, Stamens, dorsal and ventral view; G, Pistillate flower adaxial and lateral view; H, Style and stigmatic band, ventral and dorsal views; I, Cross section of young capsule; J, Capsule. All from Calaramo 18051.

FIGURE 2. Begonia tiradpassensis Calaramo, Rubite, & C.W.Lin. A, Matured capsules; B, Staminate flowers; C, Pistillate flower; D, Young leaves; E, Leaf position; F, Adaxial surface of mature leaf nearly folding; G, Adaxial leaf surface; H, Petiole and leaf-base attachment; I–K, Stipule; L, Growth habit; M, magnified indumentum on abaxial side.All from Calaramo 0018051.