Begonia butuanensis Bucay, Tandang & K.F.Chung, 2025

Bucay, Mark Angelo C., Tandang, Danilo N., Chen, Hong-Wun, Rubite, Rosario R. & Chung, Kuo-Fang, 2025, Morpho-anatomical description of new Begonia species (sect. Baryandra, Begoniaceae) from Butuan City, Mindanao Island, Philippines, Phytotaxa 681 (1), pp. 102-108 : 103-107

Begonia butuanensis Bucay, Tandang & K.F.Chung , sp. nov. § Baryandra

Type:— PHILIPPINES. Mindanao, Province of Agusan del Norte, western portion of Butuan City, growing on shaded rocks near a river within a public resort compound, ca. 65 masl, 15 August 2023, MAC Bucay & DN Tandang 0981 (holotype PNH, isotype HAST).

Diagnosis:— Begonia butuanensis was found in northern portion of Mindanao but resembles another Mindanao-endemic species, B. copelandii found only in Mt. Apo, southern portion of the island. Both species have ciliated hairs in the leaf margins and abaxial venation. Main difference is on the perianth size as B. butuanensis is comparatively smaller than that of B. copelandii ’s distinct big flowers. B. butuanensis also differs significantly on capsule’s lateral wing by having triangular shape with subfalcate apex (vs rectangular with subacute to truncated apex), puberulous peduncles (vs glabrous), and generally orbicular to slightly ovate lamina with rounded to obtuse apices (vs ovate with obtuse to acuminate apices).

Monoecious, lithophytic, perennial, rhizomatous herb with creeping, stout rhizome. Rhizome dark green to dark brown, fleshy, glabrous, and lenticelate, 5–6.5 cm × 10–12 mm, internodes 4–10 mm. Stipules subpersistent, light green to red, triangular, 10–12 × 3–4 mm, herbaceous, glabrescent, keeled, sometimes having green to pale red hairs along keel, cucullate, margin entire, apex aristate, arista 4–5 mm long. Leaves alternate; petioles terete, fleshy, generally ascending, red, 35–90 × 3–5 mm, setose with white to light brown hairs; lamina orbicular sometimes slightly ovate, 39–50 mm from the point of attachment to apex, 53–60 mm from basal lobes to tip, 52–57 mm wide, basal lobes rounded, 20–30 mm wide, sometimes shallowly overlapping, hypodermal layer present, margins with ciliate red hairs, entire, sometimes shallowly undulate, apex rounded to obtuse, adaxial surface light to dark green when mature, light purple when young, glabrous, abaxial surface light green, glabrous, venation 5–7 palmate, dichotomously branching, distinct white to pale green coloration of primary and secondary veins, slightly depressed on the adaxial surface, slightly raised on the abaxial surface, stomata in helicocytic clusters of 2–4. Inflorescences axillary, bisexual, 15–25 cm long, racemose, dichotomously branching 2–3 times; peduncle erect, light brown, 10–15 cm long, sparse to dense white hirsute hairs; bracts caducous, light brown, boat-shaped, lowest pair 5–7 × 2–4 mm, glabrous, apex acute, margin entire. Staminate flower: pedicel 5–10 mm long, light pink, glabrous, tepals 4; outer tepals 2, orbicular to oblong, pink, 6–9 × 4–7 mm, glabrous, apex rounded, margins entire; inner tepals 2, obovate to lanceolate, pink, 7–8 × 3–4 mm, glabrous, apex rounded to cordate, margin entire; androecium zygomorphic, 3–4 mm across; stamens 20–37, filament 1–2 mm long, united at base; anthers obovoid 0.4–0.6 mm long, apex rounded. Pistillate flowers: pedicel 5–11. mm long, glabrous; tepals 4; outer tepals 2, orbicular, pink on adaxial surface, red in abaxial surface, 6–9 × 5–6 mm, apex rounded, margins entire, glabrous; inner tepals 2, oblong-obovate, 6–7 × 1–2 mm, pink, apex rounded to cordate, margins entire, glabrous; styles 3, yellow, ca. 2 mm long, united at base; stigmas, spiral and densely setosepapillose, pale green, oblong in general outline, ca. 0.2 mm wide; ovary trigonal-ellipsoidal, ovate to oblong outline, green with red outline, 4–5 × 2–3 mm, 3-locular, placentae axial bifid, glabrous; wings 3, unequal, cup-shaped, base rounded, apex truncate, red; abaxial wing truncate, 4–5 × 2–3 mm, two lateral wings same shape but smaller, 4–5 × 3–4. mm. Capsule: pedicel 8–9 × 0.6–1 mm, body ovoid 4–6 × 8–10 mm (wings included), nodding,, with subequal wings, red, abaxial wing triangular, apex subfalcate, base obtuse, 4–5 × 6–8 mm, lateral wings uneven, same shape but smaller than abaxial wing, 4–5 × 6–7 mm.

Notes:— Amongst other Mindanao Baryandra species, orbicular leaves were initially observed only on B. butuanensis , as most of the orbicular to suborbicular species in the Philippines are Palawan endemics. However, upon examination of other specimens from Mindanao, it was found that the B. copelandii syntype in Berlin [B100366047] includes a plant with leaves that are broadly ovate to orbicular with a rounded apex, which resembles those of B. butuanensis . Hence, further comparison between B. butuanensis and B. copelandii was carried out. The variation in the B. copelandii syntypes, in particular the presence of both ovate-orbicular leaves and ovate leaves, was not indicated on the protologue. The original description indicated that its leaves are ovate with a cordate base and acuminate apex—which are indeed also observed in some leaves of the same syntype in Berlin. Another syntype deposited in PNH (of the same collection Copeland E.B. 1255) was examined which matched the protologue description of B. copelandii ’s leaves. These observations show the plasticity of leaf forms of B. copelandii which was not documented in the protologue, hence the necessity to examine all available syntypes. Upon comparing B. butuanensis with the B. copelandii syntypes, more differences and similarities between the two species where observed ( Table 1). One of the most obvious differences to notice is the perianth size difference which Merrill (1912) also emphasized in his B. copelandii description; in both syntypes, the ‘unusually large flowers’ with ‘comparatively large, unequally 3-winged capsules’ as described by the author were evident.

Distribution and Ecology:— The species was found only in one locality in the western portion of Butuan city, and only two subpopulations were found in the area ( Fig. 4 ). It grows along shaded streams where the individuals carpet rocky surfaces.

Etymology:— The specific epithet, “ butuanensis ” is derived from the type locality, Butuan City, province of Agusan del Norte, Mindanao island.

Phenology:— The plant was observed to be on the reproductive phase in the months of July to August.

Proposed Conservation Status:— Assessment of the proposed conservation status follows the IUCN Red List Categories and Criteria (2024). Based on observation of the type locality, the population of the plant occupies less than 400 square metres, and with only ca. 150 individuals observed. Based on personal observation of the habitat from 2010, there is an evident decline of its population size mainly attributed to habitat quality alteration restricting its observed Area of Occupancy (AOO) (Criteria A2a,b,d) and thereby causing the possible irreversible decline on its populations, subpopulations and mature individuals on the single locality where it was found (Criteria B2a,c(ii, iii, iv). Currently, the area is within a property of a freshwater resort where visitors bathe. Possible disturbance due to unregulated collection and destruction of habitat due to possible future construction activities may pose significant irreversible risk of extinction to the observed type population. It has to be noted that as early as 2010, adjacent river systems with suitable conditions for Begonia ’s growth were also assessed but no other B. butuanensis populations were observed. This current small, and further declining population are the only known B. butuanensis population (Criteria C2a(i, ii)). We hereby recommend the species to be listed as Critically Endangered A2abd; B2a,c(ii, iii, iv); C2a(i, ii).

Figures

FIGURE 4. Map fo the general location of the type locality. Map by MACB.