Begonia obtecticaulis Irmsch.

Moonlight, Peter. W., Jara-Muñoz, Orlando A., Purvis, David A., Delves, Jay, Allen, Josh P. & Reynel, Carlos, 2023, The genus Begonia (Begoniaceae) in Peru, European Journal of Taxonomy 881, pp. 1-334 : 92-94

16. Begonia obtecticaulis Irmsch.

Figs 1D , 2C , 6E , 24D , 33

Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie 74 (4): 600 ( Irmscher 1949) .

– Type: PERU – Huánuco Region • Yanano; [9°51′ S, 75°49′ W]; ca 1828 m a.s.l.; 13–16 May 1923; J.F. McBride 3721; holotype: F [ V0360598F ] .

Brako & Zarucchi (1993: 194); León & Monsalve (2006: 167).

Etymology

The epithet derives from the Latin words ‘ obtectus ’ and ‘ caulis ’, meaning ‘hidden’ and ‘stem’. This refers to the large, persistent stipules that clasp the stem and hide it from view.

Selected specimens examined

PERU – San Martín Region: Prov. Huallaga • Valley of río Apisoncho , 30 km above Jucusbamba; 7°55′S, 77°10′ W; 2600 m a.s.l.; 25Aug. 1965; A.C. Hamilton & P.M. Holligan 1421; K, NY . – Huánuco Region: Prov. Marañón • route west of Uchiza ; 8°36′29″ S, 76°40′42″ W; 1464 m a.s.l.; 9 Feb. 2016; P.W. Moonlight & A. Daza 208; E [ E00885461 ], G, MO, MOL • ibid.; 8°38′43″ S, 76°48′55″ W; 2086 m a.s.l.; 9 Feb. 2016; P.W. Moonlight & A. Daza 212 ( E [ E00885463 ], MOL, P • Dist. Cholón, San Pedro de Chonta , retorno desde el campamento hacia el pueblo San Pedro de Chonta; 8°38′13.42″ S, 76°53′08.57″ W; 3200 m a.s.l.; 21 Jul. 2021; P. González & P. Arista 10016; USM.

Description

Caulescent herb, to 1.5 m high. Stem erect, branching; internodes to 9.5 cm long, to 8 mm thick, succulent, pale green to dark red, glabrous. Stipules in unequal pairs, persistent, lanceolate to broadly ovate, clasping the stem, 9–35 × 4–18 mm, apex acute, base cuneate, translucent, pale green to brown, glabrous, margin entire, aciliate. Leaves> 5, alternate, basifixed; petiole 0.8–4.5 cm long, pale green to red, glabrous; blade asymmetric, lanceolate to ovate, to 9 × 3.5 cm, succulent, apex acuminate, base transversely cordate, basal lobes rounded, sinus to 6 mm deep, margin irregularly double-dentate, ciliate, upper surface bright green, glabrous, lower surface pale grey-green, glabrous, veins palmate-pinnate, 4–6 veined from the base, with 2–4 secondary veins on the larger side, 1–3 secondary veins on the smaller side. Inflorescences 1–3 per stem, bisexual, axillary, erect, cymose, with 2 branches, bearing up to 4 staminate flowers and 8 pistillate flowers, protandrous; peduncle to 8 cm long, red, glabrous, bracts persistent, lanceolate, 7–10 × 2–3 mm, translucent, white, glabrous, apex acuminate, margin lacerate, ciliate. Staminate flowers: pedicels to 12 mm long, glabrous; tepals 2, spreading, broadly ovate, 12–14 × 12–15 mm, apex obtuse, white to pink, glabrous, margin entire, aciliate or rarely ciliate at the base; stamens 25–30, spreading, yellow, filaments 1.5–3 mm long, free, anthers ellipsoid, 1.5–2 × 0.75 mm, dehiscing via lateral slits, connectives extending to 0.4 mm, symmetrically basifixed. Pistillate flowers: pedicels to 8 mm long; bracteoles 2, lanceolate to ovate, ca 1 × 0.5 mm, translucent, white tinged pink; tepals 5, subequal, deciduous in fruit, spreading, elliptic to ovate, 7–15 × 4–6 mm, apex rounded to acute, white, glabrous, margin entire, aciliate; ovary body ovoid, ca 7 × 6 mm, white, glabrous, unequally 3-winged, wings triangular, largest ca 10 × 10 mm, smallest ca 10 × 3 mm; 3-locular, placentae branches divided, bearing ovules on both surfaces; styles 3, yellow, free, ca 5 mm long, irregularly 2–5 times-divided, stigmatic papillae in a spirally twisted band. Fruiting pedicel to 18 mm long. Fruit body ovoid, to 9 × 6 mm, drying brown, wings same shape as in ovary, the largest expanding 12 × 18 mm, the smallest expanding to 12 × 6 mm.

Proposed conservation assessment

Previously assessed by León & Monsalve (2006) as Endangered (EN); however, their concept of the species included specimens of B. albomaculata C.DC. Known from three populations, but the type locality has undergone severe deforestation in the last century and it was last collected there in 1923. Given its EOO of <5000 km 2, that is known from three populations, and its probable extirpation from the type locality, we assess B. obtecticaulis as Endangered (EN B1ab(iv)).

Notes

Description of the pistillate flowers made using living accession 20160137a at the Royal Botanic Garden Edinburgh.

Identification notes

Begonia obtecticaulis is one of three Peruvian caulescent begonias with large, persistent stipules that clasp the internodes and are longer than the internodes. This character is shared with B. inbrexiformis and B. serratistipula sp. nov. Begonia obtecticaulis can be distinguished from B. imbrexiformis sp. nov. by its palmate-pinnate (vs pinnate) leaf venation and from B. serratistipula sp. nov. by the entire margins to its stipules (vs lacerate in the bottom third).

Distribution and ecology

Endemic to Peru and known from San Martín and Huánuco Regions ( Fig. 24D ). Found in lower, middle, and upper montane forest at an elevation of 1400–3200 m a.s.l. The species has most frequently been collected on the margins of humid forests, particularly in areas of transition to drier Andean shrublands. There are only a few natural areas of dry shrubland in the Andes of San Martín and Huánuco Regions at the elevation favoured by B. obtecticaulis but some, such as Ongón District, remain poorly collected.

Figures

Fig. 1. Leaf margins of Peruvian Begonia. A. Entire, aciliate margins (B. stenotepala A.DC.). B. Crenate, aciliate margins (B. joshii Moonlight). C. Denticulate, ciliate margins (B. acerifolia Kunth). D. Irregularly double-dentate, ciliate margins (B. obtecticaulis Irmsch.). E. Serrulate, aciliate margins (B. glauca (Klotzsch) Ruiz & Pav. exA.DC.). F. Serrate, ciliate margins (B. foliosa Kunth). Photographs taken by D.A. Purvis & P.W. Moonlight in the living collections of the Royal Botanic Garden Edinburgh.

Fig. 2. Venation in Peruvian Begonia. A. Pinnate venation (B. yaracuyensis Moonlight). B. Pinnate venation, 3-veined from the base (B. glabra Aubl.). C. Palmate-pinnate venation (B. obtecticaulis Irmsch.). D. Palmate venation with one primary vein (B. stenotepalaL.B.Sm. & B.G.Schub.).E. Palmate venation (B. lamolina Moonlight). F. Peltate venation with one primary vein (B. acerifolia Kunth.). G. Peltate venation (B. joshii Moonlight). Primary veins are shown in white, secondary veins from the petiole insertion in blue, and secondary veins from the primary veins in green. Photographs taken by D.A. Purvis & P.W. Moonlight in the living collections of the Royal Botanic Garden Edinburgh.

Fig. 6. Styles and stigmas in Peruvian Begonia. A–C. Bifid styles. D. Reniform styles. E–F. Irregularly multifid styles. A. Three styles and stigmas of B. bracteosa A.DC. B. Three styles and stigmas of B. glabra Aubl. C. Single style and stigma of B. yuracyacuensis Moonlight sp. nov. D. Three styles and stigmas of B. pedemontana Moonlight sp. nov. E. Three styles and stigmas of B. obtecticaulis Irmsch. F. Single styles and stigma of B. pleiopetala A.DC. Photographs taken by D.A. Purvis & P.W. Moonlight in the living collections of the Royal Botanic Garden Edinburgh.

Fig. 24. Distribution ofBegonia sect.Cyathocnemis (Klotzsch)A.DC. in Peru and surrounding countries. A. B. amoeboides Moonlight (red) andB. imbrexiformis Moonlight sp. nov. (blue).B. B. bracteosaA.DC. (red) and B. longinqua Moonlight (blue). C. B. cyathophora Poepp. & Endl. (red), B. serratistipula Moonlight sp. nov. (blue) and C. vargasii Moonlight sp. nov. (green). D. B. lamolina Moonlight (red), B. lophoptera Rolfe (blue) and B. obtecticaulis Irmsch. (green). Black lines indicate country borders, grey lines indicate major administrative divisions, blue lines indicate rivers, and shading indicates elevation.

Fig. 33. Begonia obtecticaulis Irmsch. A. Habit. B. Leaf, abaxial surface. C. Leaf, adaxial surface. D. Stipule. E. Inflorescence. F. Bract. G. Pistillate flower, side view. H. Pistillate flower, front view. I. Cross section of ovary. J. Largest tepal of the pistillate flower. K. Smallest tepal of the pistillate flower. L. Pistils, side view. M. Pistils, front view. N. Staminate flower, side view. O. Staminate flower, front view. P. Androecium, side view. All photographs taken by D.A. Purvis in the living collections of the Royal Botanic Garden Edinburgh (Accession 20160137a, grown from seeds collected as part of P.W. Moonlight & A. Daza 209).