Begonia thyrsoidea 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 : 298-300

75. Begonia thyrsoidea Irmsch.

Figs 90B , 94

Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie 74: 610 ( Irmscher 1949).

– Type: PERU – Cusco Region: Prov. Calca • Lares Valley between Calca and Pasto Grande ; [12°46′ S, 72°09′ W]; 1400–1500 m a.s.l.; 11 Mar. 1929; A. Weberbauer 7927; lectotype: B [ B100186590 ], designated by Moonlight & Tebbitt (2016: 119); isolectotypes: B [ B100186591 ], BM [ BM000926667 ], F [ V0042331 F], GH [ GH00068288 ], NY [ NY01085846 ], U [ U0139626 ], US [ US00115468 ].

Brako & Zarucchi (1993: 195); León & Monsalve (2006: 169); Moonlight & Tebbitt (2016: 119).

Etymology

Named for the resemblance of the unusual androecium of the species to a thyrsus, a wand or staff from ancient Greek mythology.

Specimens examined

PERU – Puno Region: Prov. Carabaya • Dist. San Gabán, between Ollachea and San Gabán, km 259+200, below the hydroelectric substation San Gabán II; 13°38′ S, 70°27′ W; 1450–1555 m a.s.l.; 9 Jan. 2015; M.C. Tebbitt & A. Daza 809; E [ E01059318 ], MOL.

Description

Caulescent, tuberous herb, to 15 cm high. Tuber ellipsoid to sub-globose, 1–3 × 0.5–1 cm, with 1 growing point. Stems 1–5, erect, unbranched or few-branched; internodes to 7.5 cm long, to 1 mm thick, wiry, pale red, glabrous to sparsely tomentose. Stipules persistent, ovate to lanceolate, 1–3 × 0.5– 1 mm, apex acute, aristate, translucent, pale green, glabrous, margin irregularly-lacerate, ciliate. Leaves 3–7 per stem, alternate, basifixed; petiole 0.5–4.5 cm long, pale red, glabrous to sparsely tomentose; blade asymmetrical, broadly lanceolate to ovate, to 7 × 7 cm, succulent, apex acute, base truncate to cordate, basal lobes not overlapping, sinus to 18 mm deep, margin crenate-lobed, the lobes dentate, ciliate, upper surface dark green, sparsely to moderately pilose, lower surface pale green flushed purple, sparsely pilose to densely pilose on the veins, veins palmate-pinnate, 6–9 veined from the base, with 2–4 secondary veins on the larger side, 1–3 secondary veins on the smaller side. Inflorescences 1–6 per stem, bisexual, axillary, erect, an asymmetrical cyme, with 2–3 branches, bearing up to 2 staminate flowers and 1 pistillate flower, protandrous; peduncle to 7.5 cm long, pale red, glabrous to sparsely pubescent, bracts persistent, oblong to narrowly ovate, 2–4 × 1–2 mm, translucent, pale green, glabrous, apex acute, margin irregularly-lacerate, ciliate. Staminate flowers: pedicels to 20 mm long, glabrous; tepals 4, spreading, outer 2 ovate, 4–9 × 3–4 mm, apex rounded, white, tinged red outside, glabrous, margin entire, aciliate, inner 2 elliptic to oblong, 3–7 × 2.5–4 mm, apex obtuse, white, glabrous, margin entire, aciliate; stamens 15–20, projecting, yellow, filaments 0.5–1.5 mm long, fused into a 2–2.75 mm long column, anthers cuboid, ca 0.75 × 0.5 mm, dehiscing via lateral slits, connectives not extended, symmetrically basifixed. Pistillate flowers: pedicels to 17 mm long; bracteoles absent; tepals 5, subequal, deciduous in fruit, spreading, narrowly elliptic to obovate, 4–5.5 × 1.5–3 mm, apex obtuse, white tinged red outside, glabrous, margin entire, aciliate; ovary body ellipsoid to obovoid, 2–4 × 3–5 mm, green tinged purple, glabrous, unequally 3-winged, wings triangular, largest 2–5 × 2–2.5 mm, smallest 3–5 × ca 0.5 mm; 3-locular, placentae branches divided, bearing ovules on both surfaces; styles 3, yellow, fused at the base, 2.5–3.5 mm long, once-divided, stigmatic papillae in a spirally-twisted band. Fruiting pedicel to 1.7 mm long. Fruit body ovoid, to 7 × 4 mm, drying brown, wings same shape as in ovary, the largest expanding to 9 × 7 mm, the smallest expanding to 8 × 3 mm.

Proposed conservation assessment

Assessed by León & Monsalve (2006) and Moonlight & Tebbitt (2016) as Data Deficient (DD). The latter authors noted that they were unable to locate the species at its type locality during fieldwork in either 2014 or 2015, and that the area has undergone widespread deforestation. We consider it appropriate to reassess B. thyrsoidea as Endangered (EN B1ab(iii)).

Identification notes

Unique among small tuberous begonias in Peru in its staminate flowers with its anthers united into a> 2 mm long column. It is also unusual in its asymmetrical inflorescences, which are only found amongst tuberous Peruvian begonias in members of the octopetala group of B. sect. Eupetalum with many more tepals on both the staminate and pistillate flowers.

Distribution and ecology

Endemic to Peru and known from Cuzco and Puno Regions ( Fig. 90A ). Found in lower montane forests at 1400–1555 m a.s.l. on moist, shaded cliffs. As a tuberous herb, B. thyrsoidea presumably dies back to its tuber in the dry season and flowers in the wet season (January to March).

Figures

Fig. 90. Distribution of the Begonia sect. Ignota in Peru and surrounding countries. A. B. bifurcata L.B.Sm. & B.G.Schub. (red), B. erythrothrix Tebbitt & Moonlight (red), and B. occultata J.P.Allen & Moonlight sp. nov. (green). B. B. speculum Moonlight & Tebbitt (red), B. thyrsoidea Irmsch., and B. urubambensis Tebbitt (green). Black lines indicate country borders, grey lines indicate major administrative divisions, blue lines indicate rivers, and shading indicates elevation.

Fig. 94. Begonia thyrsoidea Irmsch. A. Habit. B. Staminate flower, side view. C. Pistillate flower, side view. Illustration by Peter Moonlight from photographs of M.C. Tebbitt & A. Daza 809 (E).