Begonia akaw Mansibang, Aumentado & Y.P.Ang, 2023

Collantes, Yu Pin Ang John Paul R., Mansibang, Jayson, Dela Cruz, Cyrus Job P., M. Aumentado, Jamieann, Bimeda, Shane B., Callado, John Rey, Fritsch, Peter W. & Bustamante, Rene Alfred Anton, 2023, Two new species of Begonia (Begoniaceae) from Aurora Memorial National Park, Luzon Island, Philippines, Phytotaxa 609 (4), pp. 253-264 : 258-262

Begonia akaw Mansibang, Aumentado & Y.P.Ang , sp. nov.

§ Petermannia ( Figure 4 & 5 ).

Type:— PHILIPPINES. Luzon, Aurora Province, Municipality of Maria Aurora, Barangay Villa Aurora , Sitio Dimani , primary forest, elevation ca. 500 m, 15°41’ 36.5274”N, 121°21’32.0106”E, 29 June 2022, AAMNP173 (holotype PNH, isotypes BRIT, CAHUP) .

Diagnosis:— Begonia akaw belongs to B. sect. Petermannia ( Klotzsch 1854: 124; de Candolle (1859:128) in having an erect habit and protogynous inflorescence ( Doorenbos et al. 1998). It resembles B. ramosii Merr. (1911: 388) in having erect, rarely branched stems, few glabrous, long-ovate leaves, and a clustered terminal inflorescence of staminate flowers with two tepals. Begonia akaw differs from B. ramosii by having larger stipules [(10–)15–21 × 8–10 mm (vs. 10–15 × ca. 5 mm)], longer inflorescences (4.5–12 cm vs. <4 cm), obliquely ovate bracts (vs. orbicular), larger tepals on staminate flowers (12–17 × 10–13 mm vs. ca. 8 × 7 mm), a solitary pistillate flower (vs. in pairs), larger tepals on pistillate flowers (14–15 × 8–13 mm vs. 9–10 × ca. 6 mm), and a larger ovary (ca. 18.5 × 8 mm vs. ca. 10 × 4 mm) ( Table 2 ).

Description:— Lithophytic herb, monoecious, erect, lower parts of the stems prostrate or ascending, ca. 30 cm high. Stem terete, unbranched, with occasional shallow and longitudinal groove, pale green, 3–5 mm in diam., subglabrous, glabrescent, with inconspicuous microscopic indumentum, internodes (1.5–)25–60(–85) mm long. Stipules persistent, pale green, hyaline, ovate to oblong-ovate, obliquely inequilateral, (10–)15–21 × 8–10 mm, abaxially and adaxially glabrous, shallowly keeled, margin entire, apex cuspidate, cusp ca. 1.5 mm long. Leaves alternate; petiole terete, pale green, succulent, 4.0–9.0 × 0.3–0.4 mm, glabrous; lamina asymmetric, basifixed, oblong-ovate, 13.3–17.2 × 4.3–8.0(–10.0) cm, glabrous, adaxially olive green, abaxially pale green, veins raised prominently; base obliquely and prominently cordate on one side of lamina, both lobes rounded, unequal in length, margin very shallowly serrate, apex acuminate; venation basally ca. 8-palmate, branching dichotomously or nearly so, veins sunken adaxially and raised abaxially. Inflorescence terminal, bisexual, protogynous, panicle 4.5–12 cm long, staminate flowers initially clustered, maturing into a solitary monochasial raceme, peduncle 24–50 mm long, glabrous, green, reddish pink at nodes, pistillate flower solitary, axillary on terminal leaf node, basal to staminate flowers along the same panicle. Bracts sub-persistent, hyaline, white, obliquely ovate, consistent in size throughout inflorescence, (12–)18–22 × (12–) 15–18 mm, glabrous, margin entire, apex mucronate. Staminate inflorescence: pedicel 11–21 mm long, glabrous, tepals 2, predominantly white suffused with pink at base, venation distinct, pinkish, oblong-ovate to elliptic,12–17 × 10–13 mm, glabrous, margin entire, apex rounded, androecium zygomorphic, filament 0.3–1 mm long, fused at base; stamens yellow, 18 to 20, oblong in outline, apex rounded, 1.5–2.0 mm long, locules 2. Pistillate inflorescence: pedicel 16–17 mm long, glabrous; tepals 5, white to pale pink with distinct pinkish venation, subequal, glabrous, margin entire, inner tepals orbicular-obovate, ca. 15 mm × 8–11 mm, apex rounded, outer tepals somewhat broader, orbicular-ovate, 14–15 × 12–13 mm, apex rounded; styles yellow, forming 3 divided arms, each arm forked at distal half, ca. 8 mm long, twisted and papillose all around; ovary trigonous-ellipsoid, ca. 18.5 × 8 mm; locules 3, placenta bifid, wings 3, subequal, dorsal wing oblong-lunate, larger than 2 lateral wings, rounded proximally, truncate to subtruncate distally, 17–20 × ca. 9 mm, lateral wings triangular, acute to obtuse proximally, truncate distally, ca. 17 mm × 8 mm, base rounded to subacute. Capsule recurved on stiff pedicel, pedicel 16–17 mm long, dorsal wing distinctly larger than lateral wings, nodding when mature, 2 lateral wings cucullate to form a splash cup, dehiscing along ovary wing attachments when dried, 16–20 × ca. 18 mm.

Etymology:— The epithet “ akaw ” is a Balereño word used to convey awe, disbelief, or surprise. The species had been documented and observed on multiple occasions, being misidentified as B. ramosii . This can be considered as a case of an overlooked undescribed species, which is true for other threatened flora in the country ( Daipan et al. 2022).

Distribution and habitat:— Aside from the locality from which the type was collected in AMNP ( Figure 6 ), local populations were also found in the Caunayan Falls and Ditumabo Falls areas, San Luis; the vicinity of Bulawan Falls, Dimayuga; and Amro River Protected Landscape, Dilasag. It occurs locally on rock walls with dripping water, streams, waterfall areas, deeply shaded humus-rich forest soil, and along forest trails. This taxon was often observed growing sympatrically with B. droseroides , B. cf. megacarpa Merr. (1914: 378) , and B. aff. negrosensis Elmer (1910: 736) , among other shade-tolerant herbs and rock wall associates.

Phenology:— This species flowers and fruits year-round.

Proposed conservation assessment:— Because the localities of Begonia akaw have developed into tourism spots, the local rock wall populations of Caunayan Falls and Ditumabo Falls, Barangay San Luis have been observed to be largely removed. Furthermore, the creation of logging trails, forest conversion, and clearing also devastate localities where B. akaw occurs. From our surveys, we estimate the EOO is to be <800 km 2 with an AOO of about 20 km 2 These threats for B. akaw satisfy the IUCN 15.1 Red List EN (Endangered) Criteria B1ab (ii,iii)+2ab(ii,iii) ( IUCN Standards and Petitions Subcommittee, 2022).

Notes:— The stem and stipule may appear glabrous in fresh specimens. However, there are minute trichomes that can only be seen with a dissecting scope at 160×.

Other specimen examined:— PHILIPPINES. Luzon, Aurora Province, Municipality of Maria Aurora, Barangay Villa Aurora, Sitio Dimani , primary forest, elevation 535 m, 15°40’51.654”N, 121°23’37.9932”E, 26 February 2022, PTI-AMNP-1-46 ( PNH, CAHUP, PPC) .

Figures

FIGURE 4. Begonia akaw. A. Habit; B. Stipule; C. Bract; D. Inflorescence; E. Androecium; F. Pistillate flower lateral view; G. Ovary cross section. Illustrated by J. Mansibang based on AAMNP173 (PNH, BRIT, CAHUP).

FIGURE 5. Begonia akaw. A. Habitat and habit; B. Stem; C. Stipule; D. Leaf adaxial (left) and abaxial (right) surface; E. Inflorescence showing bracts; F. Inflorescence showing peduncle; G. Staminate flower ventral view; H. Staminate flower ventral view, a variant with rounder tepals; I. Staminate flower lateral view; J. Pistillate flower ventral view; K. Pistillate flower lateral view showing ovary; L. Ovary cross section; M. capsule. All photos by Y.P. Ang.

FIGURE 6. Map of Aurora Province showing the locality of B. masilig and B. akaw (star).