Begonia humillima L.B.Sm. & Wassh., 1983

Moonlight, P. W. & Jara-Muñoz, A., 2017, A revision and recircumscription of Begonia Section Pilderia including one new species, Phytotaxa 307 (1), pp. 1-22 : 12-14

3. Begonia humillima L.B.Sm. & Wassh. ( Fig. 4 ; Fig. 7c )

Phytologia, 53: 297, pl. 1 (1973). Type: VENEZUELA. Estado Yaracuy, Montaña de Maria Lionza, virgin evergreen forest, Quebrada Quibayo, vicinity of sanctuary Tres Casitas, al sur de Quibayo, al sur de Chivacoa, creeping along rocks and ledges, 10˚6–7’ N, 69˚55’ W, alt 800–900m, 13 March 1981, J. A. Steyermark, C. Sobrevila, D. Fernandez, & A. Hernandez 12511 (holotype VEN; isotype US [ US 00425078], US [ US 00115338]) .

Plants caulescent, scandent herbs, 10–15 cm high; stem repent, rooting at the nodes, flexuous, frequently branching; internodes 0.5–4 cm long, to 1.5 cm thick, succulent, sparsely to moderately villous, hairs to 2 mm; stipules persistent, lanceolate, 4–8 × 1.5–5 mm, villous, apex mucronate, margins entire, aciliate. Leaves alternate, spread along the stem, more than 5, basifixed; petioles 0.5–9.5 cm long, very densely villous to sparsely villous with age, hairs to 2 mm; lamina asymmetric, transverse, ovate, 7–13.5 × 2.5–6.5 cm, apex acuminate, base cordate, sinus to 1.3 cm deep, lobes not overlapping to overlapping, acuspidate, margins double-dentate at the apex, teeth 1–4 mm long, long-ciliate, the upper surface bullate, green, with 2 to 3, glandular, villous hairs between each tertiary vein connected to a bifid or trifid gland visible within the leaf lamina, the gland drying black, the veins glabrous to sparsely-villous at the petiolar insertion, the lower surface even, pale green, glabrous between the tertiary veins, the veins densely villous to very-densely villous towards the petiolar insertion; venation palmate-pinnate, with 4–5 veins from the base, with 5–7 lateral veins on the widest side of the lamina, and 4–6 lateral veins on the narrow side. Inflorescences: axillary, terminal, repent, 6–10 cm, densely glandular-villous throughout, thyrsoid with 2 to 4 lateral branches, lateral branches cymose, each cyme branching 1 time, protandrous; peduncle to 4 cm long, internodes to 2.5 cm long, decreasing to ca. 5 mm long at the apex, peduncles of cymes 2–5 mm; bracts persistent, lanceolate, 2–5 × 0.5–2.5 mm, membranous, villous, apex obtuse, margin entire to lacerate, ciliate; pedicels of male flowers 4–10 mm long, fibrous; pedicels of female flowers 8–18 mm long, fibrous. Male flowers: tepals 4, membranous, sparsely villous inside and outside, the outer ovate, 5–9 × 4–8 mm, apex rounded, white, the inner elliptic, 4–7 × 2 mm, apex acute, white; stamens 15–25, united along the length of a 1 mm long column, orange; filaments 0.5–1 mm, anthers linear, 0.5 × 0.2 mm, obtuse, dehiscing through lateral slits, the connective not projecting. Female flowers: bracteoles 2, persistent, ovate, 3–5 × 2–4 mm, membranous, sparsely-villous, margins lacerate, densely ciliate; tepals 5, persistent in fruit, white, subequal, lanceolate, 3.5–5 × 1–2, margins entire, aciliate; ovary body globose, 4–6 × 4–5 mm, sparsely glandular-pilose, white, 3-locular, unequally 3-winged, the wings sparsely glandular-pilose, largest wing triangular, ascending, widest 1/3 of the length towards the apex, 8–10 × 5–8 mm, apex acute, base cordate, margins entire, ciliate, smallest 2 triangular, ascending, 4–6 × 5–8 mm, apex acute, base cordate, margins entire, ciliate; placentae axile, simple, ovuliferous all over; styles 3, 3 mm long, bifid 1 mm from base, the branches erect, spirally twisted two times, greenish-yellow, persistent in fruit. Fruiting pedicel elongating to 20mm. Fruit ovate, enlarging to 4 × 6 mm, largest wing the same shape as in the ovary, enlarging to 18 × 7 mm, the smallest enlarging to a triangular wing 12 × 8 mm. Seeds globose, 0.2 × 0.2 mm.

Distribution and habitat:— Venezuela. Begonia humillima is known only from four collections on Sorte Mountain in María Lionza National Park in the State of Yaracuy at 780–1000 m. The species is described as creeping along rocks in humid evergreen forest.

Taxonomic notes:— Begonia humillima is a highly distinct species and easily distinguished from all other Andean species in the genus by its combination of a creeping habit and thin, semi-transparent, transverse, ovate and bullate leaves. Bullate leaves are common in Andean Begonia but are not elsewhere found in combination with the habit and described for this species.

Although its transverse, ovate leaves and repent habit superficially resemble B. glandulifera and B. jenmanii , we suggest B. humillima is most closely related to B. buddleiifolia and B. tepuiensis . These three species share simple placentae (those of B. glandulifera and B. jenmanii are bilamellate) and have more similar upper leaf indumenta. Begonia glandulifera , B. jenmanii , and B. mariannensis have single, glandular-pilose or glandular-villous hairs throughout their upper leaf lamina whereas B. buddleiifolia , B. humillima and B. tepuiensis have groups of glandular hairs between the tertiary veins connected to multifid glands within the leaf lamina, which is distinct from a villous or lanate and sometimes stellate indumentum on their venation.

IUCN Redlist Assessment:— Begonia humillima is known from a single population with an AOO and EOO of ca. 10 km 2. This population grows within the Monumento Natural María Lionza protected area. Although this park likely suffers from visitor pressure, no information is available on population trends within the species and an assessment of Vulnerable (VU D2) is therefore appropriate.

Additional specimens examined:— VENEZUELA: Yaracuy: Urachiche, Monumento Natural María Lionza, Cordillera de la Costa, al sur de Chivatoa, subida Quebrada Quibayo-La Fortaleza-Tres Casitas, Tres Casitas, entre Tres Casitas y 1000 m.s.n.m., 10˚6’ N, 68˚55’ W, alt. 780–790 m, 26 iii 2004, W. Meier et al. 10322 ( G) ; Urachiche, Monumento Natural María Lionza, Cordillera de la Costa, al sur de Chivatoa, subida Quebrada Quibayo-La Fortaleza-Tres Casitas, entre Tres Casitas y 1000 m.s.n.m., 10˚6’ N, 68˚55’ W, alt 780–1000 m, 26 iii 2004, W. Meier et al. 10327 ( US [ US 00901446]) ; Urachiche, Monumento Natural María Lionza, Cordillera de la Costa, al sur de Chivatoa, subida Quebrada Quibayo-La Fortaleza-Tres Casitas, Tres Casitas, 10˚6’ N, 68˚55’ W, alt 780–790 m, 26 iii 2004, W. Meier et al. 10345 B ( US [ US 00901447]) .

Figures

FIGURE 4. Begonia humillima L.B.Sm. & Wassh. A. Habit; B. Male flower (front view); C. Female flower (side view); D. Fruit (sidetop view, dissected); E. Androecium (side view) F.Group of styles and stigmas (side view). Reproduced from (Smith & Wasshausen 1983) with the permission of Phytologia.

FIGURE 7. Distributions of species in Begonia sect. Pilderia (Klotzsch) A.DC. A. B. buddleiifolia A.DC.; B. B. glandulifera Griseb.; C. B. humillima L.B.Sm. & Wassh.; D. B. jenmanii Tutin; E. B. mariannensis Wassh. & T.McClellan; F.B. tepuiensis Moonlight & Jara.