Begonia tanauanensis Tandang, Bucay & K.F.Chung

Bucay, Mark Angelo C., Tandang, Danilo N., Rubite, Rosario R., Jr, Edison Jallores & Chung, Kuo-Fang, 2024, A new Begonia species (sect. Baryandra, Begoniaceae) from Batangas Province, Luzon Island, Philippines, Phytotaxa 641 (4), pp. 277-285 : 278-284

Begonia tanauanensis Tandang, Bucay & K.F.Chung , sp. nov.

§ Baryandra

Type: — PHILIPPINES. Luzon, Province of Batangas, southern portion of Tanauan City, growing on shaded moist boulders of rocks along streams, near waterfalls, and within a Lansium domesticum plantation at elevation ca. 65 masl, 14 February 2023, MAC Bucay with DN Tandang 0009 (holotype PNH, isotype HAST) .

Diagnosis: —Among the tallest of the currently described Philippine Baryandra species in its section, B. tanauanensis has the closest vegetative and reproductive structures to B. chingipengii from Gabaldon, Nueva Ecija in Eastern Luzon by having broad ovate leaves, boat-shaped bracts and light pink flowers. However, B. tananuanensis’ s stipules have no keels, or sometimes partly keeled (versus strongly keeled in B. chingipengii ), solid green adaxial leaf surface (versus dark green with prominently white midrib and veins of B. chingipengii ), setose abaxial leaf surface and petioles (versus tomentose), and glabrous leaf margins (versus ciliated leaf margins). Other key differences are summarized in Table 1 .

Monoecious, lithophytic, perennial, rhizomatous herb with creeping, stout rhizome. Rhizome light brown, fleshy, glabrous, and lenticelate, 3–12.5 × 1.3–2 cm, internode 3.5–14 mm. Stipules persistent, cream to pale green, asymmetrically broadly ovate, 20–24 × 15–17.5 mm, herbaceous, glabrescent, sometimes having brown setose curly hairs on abaxial surface, sometimes partly keeled, cucullate, margin entire, acute to acuminate at apex with short arista at tip, 3–4 mm long. Leaves alternate, succulent, and brittle when crushed; petioles terete, fleshy, generally ascending, mostly pale green and usually tinged pinkish line on one side, 22–52 cm long, 8–14 mm in diameter at base, gradually narrowing at the middle 5–11 mm thick, 4–8 mm thick apically, sparsely to densely setose with soft brown, appressed trichomes (young petioles densely brown villose), no ring of hairs on the junction of leaf; lamina asymmetrically oblong-ovate to broadly ovate, 16–26 cm from the point of attachment to apex, 21–37 cm from longest basal lobes to tip, 12–23 cm wide, obliquely cordate base, basal lobes rounded, 6–11 cm wide, sometimes overlapping, acuminate at apex, margins with shallow irregular lobes, young leaves entire, maturing to be strongly undulate, adaxial surface dark green (in some individuals the leaves have scattered small white spots at interveins), glabrous, glossy when young, abaxial surface pale green, with appressed brown setose hairs (velvety, reddish or brownish when young), venation basally 11–13 palmate, dichotomously branching towards the margin, shallowly sunken adaxially, raised abaxially. Inflorescence axillary, bisexual, longer than the petioles, 26–80 cm long, cyme, dichotomously branching 2–7 times; peduncle erect when short to slightly arched in longer length, light brown, sometimes with shade of pink, particularly on the upper part, 21–64 cm long, sparsely hairy. Bracts caducous, pale green to pale pink, boat-shaped, lowest pair 17–21 × 14–16 mm, glabrous, apex retuse, margin entire to undulate, bracts of upper inflorescence similar in shape and colour but smaller. Staminate flower: pedicel 25–41 mm long, light to slightly dark pink at the upper portion, glabrous. Tepals 4(–5), pale pink to pink, some outer upper tepals have a deeper shade of pink basally on both surfaces; 2 outer tepals, orbicular to oblong, 14–18 × 12–14 mm, glabrous, apex rounded, slightly incurved, margins entire to sinuate; 2 inner tepals lanceolate, 9–10 × 4–5 mm, glabrous, apex rounded, but upper half slightly folded in the middle, concave at basal half, margin wavy; androecium zygomorphic, 5–6 mm across; stamens yellow, 40–44, filament light green, unequal in length, 1–2 mm long, united at base; anthers obovoid 0.6 mm × 0.6–0.8 mm, apex rounded. Pistillate flowers: pedicel 14–20 mm long, glabrous; tepals 4(–5), pale pink to dark at base on upper tepal; 2 outer tepals orbicular, 11–13 × 14–15 mm, apex rounded, glabrous, margins undulate; 2 inner tepals oblong-obovate, 6–9 × 3–4 mm, light pink to dark pink towards the base, apex rounded and wavy, lower basal half concave, glabrous on both sides; styles 3, pale green to yellow, ca. 3 mm long, united at base; stigmas, spiral and densely setose-papillose, pale green, oblong in general outline, ca. 0.3 mm wide; ovary trigonal-ellipsoidal, ovate to oblong outline, white, 7–8 × 5–6 mm (wings excluded), 3-locular, placentae axial bifid, glabrous; wings 3, unequal, base rounded, apex truncate, pale pink; abaxial wing truncate, 14–17 × 10–11 mm, two lateral wings truncate, 12–14 × 4–7 mm. Capsule: ovate 10–11 × 5–10 mm (wings excluded), nodding, pedicel, 28–33 mm, with 3 subequal wings, pale pink, abaxial wing truncate slightly larger and broader than lateral wings, 15–18 × 10–13 mm, lateral wings truncate, 13–16 × 4–9 mm.

Distribution and ecology: —It is only known from its type locality in Tanauan City, Batangas, Philippines. This unique species is found growing on boulders of rocks within a Lansium domesticum (Corrêa 1807:157) plantation, near the waterfall on moist rocks along the watercourse flows in a deeply shaded habitat at elevation 65 masl ..

Etymology: —The specific epithet “ tanauanensis ” is named after the place of its origin, Tanauan City, Batangas in southern Luzon, Philippines.

Phenology: —It bears flowers and immature fruits from February to March. It was documented bearing dried capsules during the month of May.

Proposed Conservation Status: —The type locality is within the Taal Volcano Protected Landscape (TVPL). With its known range, the plant occupies highly disturbed secondary forest vegetation, and grows in small colonies with a scattered distribution. There are around 8 subpopulations, with an approximate total of less than 200 mature individuals and with an estimated area of occupancy (AOO) of ~400 sqm.Additionally, the possibility of land clearance within the fruit crop plantation and volcanic activities of the nearby Taal volcano may pose significant pressures on the habitat and some subpopulations.

Given these combined threats, we recommend a provisional threat assessment as Critically Endangered. These observations of B. tanauanensis made in situ satisfy the IUCN Red List CR (Critically Endangered) Criteria B1ab(ii,iii,v)+B2ab(i,ii,iii,v) ( IUCN, 2022), i.e. the species has an EOO <100 km 2 and is known from only a single location with inferred and observed declines in area of occupancy, quality of habitat and number of mature individuals, and an AOO <10 km 2 at the single location with a reduction in area of occurrence, occupancy, extent and quality of habitat, and number of mature individuals.