Begonia sandsiana W.N.Takeuchi, 2013

Takeuchi, Wayne, 2013, Begonia sandsiana sp. nov. (Begoniaceae), a remarkable calciphile from the southern karst of Papua New Guinea, Phytotaxa 138 (1), pp. 31-38 : 32-37

Begonia sandsiana W.N.Takeuchi , sp. nov. ( Figs. 1–4 )

Inter species Begoniae Papuasiae sectionis Diploclinii caulibus in vivo valde magnis usque ad 110 × 2.1 cm et staminibus (3–)5(–6) distinguenda.

Type: — PAPUA NEW GUINEA. Western Province: Strickland drainage, Juha South (Bivouac 2), survey track 1 to sinkhole area, mossy montane forest, 5°53.994'S, 142°26.234'E, 910 m, 21 February 2008, Takeuchi , Gambia & Jisaka 23245 (holotype A!; isotypes E!, K!, L!, LAE!) .

Perennial herbs to 35 cm tall (height exclusive of stoloniferous axes), monoecious. Stems cylindrical, 4–11 mm diameter, monoaxial, straight, adventitiously rooting, glabrous, pithy (or hollow), articulated by transverse ridges, longitudinally wrinkled; surfaces brunnescent, chalky, conspicuously cicatrose; abscission scars crateriform, 5–10 × 4.5–6 mm; internodes 6–14 mm long. Leaves alternate, distichous, crowded in terminal sprays, obliquely spreading; stipules lanceolate-ovate, 22–31 × 4–15 mm, caducous, glabrous, chartaceous, hyaline, not venose; petioles 105–275 × (1–) 2.5–6 mm, laxly pilosulous, glabrescent, flat, thin, weak, pale brown or pink; leaf-blades ovate to orbicular-rotund, 14.3–24 × 12.5–20 cm, asymmetric (rarely ± equilateral), membranous; base obliquely cordate, sinus open or with lobes overlapping; margins ciliate, irregularly repand, toothed, or subentire (senescing leaves erose); apex acuminate, acumen ca. 0.5–2.5 × 1–2 cm; lamina surfaces olivaceous, rufous, or nigrescent, dull, bifacially set with antrorsely adpressed hairs, indument persisting, occasionally crispate; venation 5–9-palmatinerval, furcately branching towards the margin, prominulous on both sides; reticulum coarse, somewhat tessellate, obscure. Inflorescence axillary, paniculiform, to 8 cm long, dichotomously branched through (1–)2(–3) orders, pauciflorous, loose, glabrous, cernuous; peduncle 17–28 × 1–2 mm, angulate or flat; axes copiously bracteate, flaccid, filiform, furrowed, nodulose, usually brunnescent-fuliginous; bracts ovate, obovate, or orbicular, 9–13 × 7–13 mm, paired, distichous, congested, hiding axes and flower buds, membranous, persisting to post-anthesis. Male flowers (measurements from spirit-preserved material) pseudoterminal on ultimate axes, seemingly solitary; pedicels cylindrical, 8–10 × 0.8–1.1 mm, not articulated; tepals 4 in 2 unequal pairs, free, concave; outer (larger) tepals obtusely ovate, 5.3–7.6 × 4.5–5 mm; inner (smaller) tepals lanceolate, (4.5–)5.2–6.2 × 2.7–3.5 mm, subacute, inserted at right angles to the outer pair; stamens (3–)5(–6), usually 4 stamens antetepalous and 1 in the center, free, subequal, ascending; filaments (1–)1.7–2 × 0.2–0.3 mm, incurved or not; anthers oblongoid-claviform, 1.3–1.6 × 0.6–0.8(–1.1) mm, 2-celled, basifixed, longitudinally dehiscent, latrorse, connective not prolonged. Female flowers (measurements from spirit-preserved material): pedicels as for the male but shorter, 4–7 × 0.9–1.2 mm; ovary inferior, 3-locular, unequally 3-alate, placentation axillary, ovules numerous, arising on proliferations from septae; major wing horn-like, (6–)9–13.5 × 2.5–3.1 × 1–1.5 mm, opposite an outer (large) tepal, gradually arcuate (or straight-diverging), planate, obtuse; minor wings (2) deltoid, 4–6 × 4–7.5 × 1–3 mm; tepals 3, free; outer (major) tepals 2, ovate, 9–11 × (5–) 7–8.5 mm, equal; innermost tepal smallest, elliptic-lanceolate, 8–9.2 × 3.5–4.5 mm; staminode(s) absent; styles 3, irregularly cylindrical, 3–4 mm long; stigmatic surfaces comprising nearly all of the style length, thickened, papillate, not divided, not spirally twisted, capitate or 2-lobulate (minutely T-shaped) at the top. Fruits (measurements from spirit-preserved material): 9–11 × 15–18.5(–21) mm, loculicidal, 3-lobed, solitary on ultimate axes, glabrous; pedicels 7.5–11 × 0.9–1.2 mm; major lobe 11–13.5 × 5–7.5 × 2–3 mm; minor lobes 8–10 × 5–8 × 2.5–3 mm.

Etymology: — Begonia sandsiana is named after M.J.S. Sands (Royal Botanic Gardens, Kew), a specialist in Malesian Begoniaceae .

Field characters: —Saxicolous herbs; stems adhesively rooted to limestone walls, vertically climbing, firm (not juicy), pithy, brown, terete at base, distally cylindrical, to 110 × 2.1 cm, copiously cicatricatous; abscission scars crateriform, 9–17 × 6–12 mm; stipules lanceolate-ovate, chartaceous, hyaline; leaves crowded in terminal sprays (rarely sprouting along stems), fleshy, adaxially dark dull green, abaxially glaucous; inflorescence flaccid, cernuous or hanging; bracts white, induplicative; flowers unscented; perianth (both sexes) entirely white; anthers white; stigma yellow; fruits green turning brown when mature.

Distribution: —Endemic to the Strickland drainage of Western Province, from remote and uninhabited uplands ( Fig. 5 : B).

Habitat and ecology: —Epilithic on limestone in perhumid montane forest at 910–975 m.

Phenology: —Flowering and fruiting in February.

Additional specimen examined (paratype): — PAPUA NEW GUINEA. Western Province: Strickland drainage, Juha South , mossy montane forest on limestone, 5°53.951'S, 142°26.037'E, 975 m, 18 February 2008, Takeuchi , Gambia & Jisaka 23097 (A!, BO!, LAE!) .

With respect to the reproductive structures, Begonia sandsiana is closest to B. brassii Merrill & Perry (1943: 43) of Irian Jaya, but with easily discerned differences in stem morphology, leaf shape/size, and indument. The new plant's astonishingly large stem and the inflorescences densely obscured by bracts, are instantly distinguishing. Table 1 provides a concise summary of the principal contrasts between B. sandsiana and its presumed ally.

Of the 79 Begonia Linnaeus (1753: 1056) species from New Guinea, only 7 were previously known to have male flowers with 4 tepals (section Diploclinium in Sands 2009; see also Merrill & Perry 1943, Doorenbos 1978, Doorenbos et al. 1998). Including the species described here, 4 of the Diploclinium begonias from mainland New Guinea are distinctively characterized by horned fruits and a reduced androecium with only 3–8 stamens. These features are aberrant within Diploclinium s. s. and possibly indicative of a separate section presumably comprised of Begonia brassii , B. chambersiae Takeuchi (2012: 44) , B. oligandra Merrill & Perry (1943: 44) and B. sandsiana (M. Hughes pers. comm.).

Begonia sandsiana Begonia brassii a

known only from the Strickland drainage ( PNG) at 910–975 m known only from the type locality in Papua Province

( Indonesia) at 2,300 m

always growing directly on limestone from forest undergrowth in moist gullies, not on limestone (as

far as can be determined)

rooting stems massive, to 110 × 2.1 cm in vivo, usually rooting stems delicate, considerably smaller, ca. 12 × 0.1 cm

unbranched (dry), simple or sparingly branched

petioles 10.5–27.5 cm long, glabrescent petioles 1–3 cm long, hirtellous

leaf-blades ovate to orbicular-rotund, 14.3–24 × 12.5–20 cm; leaf-blades lanceolate-elliptic, 3.5–9 × 1–3.5 cm; adaxially

bifacially adpressed-hairy; venation palmatinerval glabrous, abaxially adpressed-hairy along veins; venation

pinnatiform

stamens (3–)5(–6) stamens 4

female flowers with 3 tepals; styles unbranched female flowers with 3–4 tepals; style-branches well-developed

a. extracted from Merrill & Perry (1943), and/or refined by examination of the LAE isotype.

Figures

FIGURE 1. Begonia sandsiana W.N.Takeuchi. A, climbing stems (to 110 × 2.1 cm) adhesively rooted to limestone wall; B, in situ detail of stem, conspicuously marked by abscission scars. A–B from Takeuchi, Gambia & Jisaka 23245.

FIGURE 2. Begonia sandsiana W.N.Takeuchi. A, leaves, adaxial surfaces; B, leaf, abaxial surface. A–B from Takeuchi, Gambia & Jisaka 23245.

FIGURE 3. Begonia sandsiana W.N.Takeuchi. A, aspect; B–C, male flowers. A–C from Takeuchi, Gambia & Jisaka 23245.

FIGURE 4. Begonia sandsiana W.N.Takeuchi. A, infructescence, aspect; B, female flowers; C, fruit, proximal view; D, fruits, distal view; E, overmature fruits with germinating seeds. A–E from Takeuchi, Gambia & Jisaka 23245.

FIGURE 5. Island of New Guinea. A, Mt. Mabiom, bivouac from the Second Archbold Expedition; B, Juha South, type locality for Begonia sandsiana. Overlay (shaded area) shows distribution of the southern karst formations.