Begonia mindanaensis Warb. (1904: 55)

Naive, Mark Arcebal K., Cababan, Mc Arthur L., Lubos, Lesley C. & Hughes, Mark, 2022, Taxonomy of the genus Begonia (Begoniaceae) in Mindanao, Philippines III: New insights into the morphology and distribution of Begonia malindangensis and B. mindanaensis, Phytotaxa 564 (2), pp. 265-272 : 270

Begonia mindanaensis Warb. (1904: 55) .

Type:— PHILIPPINES. Mindanao: Davao Province, Mt. Dagatpan , June 1888, O. Warburg 14633 (lectotype B [B100238393-seen!] designated here). Fig. 3 .

Terrestrial, monoecious, herbaceous or suffrutescent plant, 25–60 cm tall. Rhizome creeping, 1.3 cm in diameter. Stem occasionally branching, erect or ascending, terete, 10–12 mm in diam., reddish green, densely scabrid, nodes swollen, maroon, internodes to ca. 8–14 cm long. Stipules narrowly ovate, concave, 10–15 × 4–6 mm, membranaceous, reddish green, pubescent, apex acute. Leaves alternate, ca. 20–40 per plant, subsessile; petiole 2–3 mm long, ca. 7 mm in diam., terete, succulent, scabrid, reddish green to maroon; lamina asymmetrical, oblong-ovate, 7–10 × 2–4 cm, coriaceous, dark green, sparsely echinate, verrucose adaxially, pale green to brownish green, glabrous to occasionally sparsely echinate abaxially, margin distantly, irregularly dentate, base obliquely asymmetrical, apex long acuminate; venation pinnate, channeled, glabrous, green to reddish adaxially, protruding, pubescent, green to reddish abaxially, midrib distinguishable, with 5–6 lateral veins on each sides, other primary veins branching dichotomously or nearly so, tertiary veins weakly percurrent. Inflorescences axillary, unisexual, 1–few flowered fascicles, congested, ca. 3 cm long; bracts broadly ovate to lanceolate, 0.6–0.8 × 3.0 mm, chartaceous, densely pubescent, pale green to reddish green, margin entire, apex acuminate. Staminate flowers pinkish white to pale pink; pedicel 10–13 mm long, whitish, terete, sparsely puberulent; tepals 4, outer tepals orbicular, 9–12 × 8 mm, glabrous adaxially, pubescent abaxially, margin entire, sparsely ciliate, apex obtusely rounded, inner tepals elliptic to obovate, 10–12 × 5 mm, glabrous, channeled, margin entire, apex emarginate to attenuate, the stamens 30–40, golden yellow; anthers elliptic, 0.5 mm long, apex obtuse; filament 0.3–0.5 mm long. Pistillate flowers pinkish; pedicel 5–8 mm long, green to reddish green, terete, pubescent; ovary trigonous-ellipsoid, reddish green to crimson red, densely pubescent, 8–15 × 5–6 mm (wings excluded), wings bluntly obtuse, 3-locular, placentation axile, bilamellate; tepals 5, glabrous adaxially, pubescent abaxially, outer tepals 2, broadly ovate, 10–12 × 7–9 mm, apex obtuse to acute, inner tepals 3, broadly obovate, 8–12 × 8–10 mm, apex obtuse to rounded; styles 3, 2–3 mm long, greenish yellow, bifid, apically forked; stigmas spirally twisted, papillose all around. Infructescence 1.5–2.3 cm long; pedicel 3–5 mm long, green, pubescent; tepals deciduous; capsule turbinate to trigonous-ellipsoid, pubescent, reddish green to crimson red, with 3-equal bluntly obtuse wings, 10–11 × 12–13 mm including wings.

Distribution:— Endemic to Mindanao, southern Philippines ( Fig. 2 ). The species has so far only been found in Davao Province (Mt. Dagatpan) and Bukidnon (Mt. Malantaw). According to Sangvirotjanapat et al. (2019), Mt. Dagatpan is probably on the southeastern side of Mt. Apo, in the municipality of Santa Cruz.

Ecology:— The species was found growing in steep slopes of lower montane primary broad-leaved forest in shaded to diffusely lit localities at 1200–1300 m above sea level.

Phenology:— Observed flowering and fruiting in the wild in the months of February, October and November.

Provisional conservation status:— So far, two localities are known for this species including its type locality. In Mt. Malantaw, a few populations were observed (with ca. 50 mature individuals) in a limited area giving an approximate area of occupancy of 8,000 km 2 when calculated in GeoCAT based on a user defined cell width of 2 km ( Bachman et al. 2011). It was found growing near human settlement, thus, these populations are prone to the effects of anthropogenic activities such as slash and burn, conversion of forest to agricultural land and poaching. Hence we propose B. mindanaensis to be provisionally treated as “Endangered” (EN B2ab[iii]), following the Red List Criteria of the IUCN Standards and Petitions Subcommittee (2019).

Additional specimens examined: PHILIPPINES. Mindanao: Bukidnon, Valencia City, Concepcion , Mt. Malantaw , elev. 1271 m, 22 nd November 2020, MA Cababan 1 (HNUL, new provincial record) .

Notes:— Begonia mindanaensis was originally described by Warburg (1904) based on his material from Mt. Dagatpan. At present, only a single sheet of the type gathering is known and we here designate it as the lectotype since Warburg (1904) did not indicate how many specimens were preserved and duplicates may therefore yet surface.

The name B. mindanaensis has been broadly applied to specimens belonging to various species of B. sect. Petermannia from Mindanao and Leyte (in Hughes et al, 2015 –), likely in part due to its geographic epithet. Closer examination of the material under this name shows a considerable variation in vestition, petiole length and leaf dentition. The type specimen is vegetative, and the protologue correspondingly lacks descriptions of the staminate and pistillate flowers. However, the hair characters mentioned in the description offer diagnostic information. The stem hairs are described in the protologue as pilis fulvis hispido, and short erect hairs are visible on the image of the type in Berlin. These differ from the much longer curled hairs which form a dense indumentum on B. ciliifera Merr. (1912: 376) , which has a similar leaf shape and habit. The hairs on the leaves are more clearly diagnostic, and described by Warburg as pilis punctiformibus parce interspersis (with sparsely dispersed punctiform hairs) which match those seen in Cababan 001 ( Fig. 1B & C ). Specimens previously determined as B. mindanaensis from near the Agusan River and Mt. Urdaneta (Elmer 13367; Merrill 7310) have leaves that are smooth and glabrous above. Here we consider B. mindanaensis to be a narrow endemic to the mountains running north-south in central Mindanao (viz. Mt. Malantaw of Bukidnon and Mt. Apo of Davao del Sur).

Figures

FIGURE 1. Begonia malindangensis Merr.A. Habit (inset:female flowers); B. Leaves, abaxial surface (above), adaxial surface below; C. Pistillate flowers; D. Bracteole; E. Cross section of the ovary; F. Staminate flower; G. Dried fruit. From MA Cababan 2. Photos by: MAK Naive (A, C, D, E) and P. Pelser & J. Barcelona (B, F, G).

FIGURE 2. Map showing the distribution of Begonia malindangensis and B. mindanaensis.

FIGURE 3. Begonia mindanaensis Warb. A. Habit; B. Leaves, adaxial and abaxial surfaces; C. Details of the stem; D. Pistillate flower, front view; E. Pistillate flower, profile view; F. Detail of ovary; G. Staminate flower; H. Fruit. From MA Cababan 1. Photos by: M.A. Cababan.