Begonia rivularis E.L. Jacques, 2018

Jacques, Eliane De Lima, 2018, Four New Brazilian species of Begonia (Begoniaceae), Phytotaxa 381 (1), pp. 86-94 : 89-93

Begonia rivularis E.L. Jacques , sp. nov. ( Figs. 3. H–M )

Begonia rivularis is most similar to B. quetamensis L.B. Sm. & B.G. Schub. , although differs by having smaller male tepals 7–14 mm long (vs. 17 mm long.) and styles bifurcate (vs. multifidis).

Type:— BRASIL. Góiás: Niquelândia, Serra Negra, 27 January 1998, S. P. Cordovil-Silva, S. C. Xavier & L. B. Lima 743 (holotype CEN!, isotype SP!).

Description:—Herbs, perennial, 20–70 cm tall, acaulous, puberulous. Cystoliths absent. Stems thick, rhizomatous; internodes indistinct. Stipules persistent, elliptic to widely triangular, papyraceous to subcoriaceous, scarious, 0.5–1.3 × 0.3–0.4 cm, margins entire to inconspicuously ciliate, apex acute or acuminate to setose, sometimes aristate on the dorsal surface. Leaves with petioles 5–25 cm long, densely to lightly pilose, trichomes simples, glandular, capitate, blades basifixed, entire, oblique, symmetrical to asymmetrical, cordiform, membranaceous, 9.5–31.5 × 6–30 cm, both surfaces puberulous, trichomes glandular, margins dentate-ciliate to serrulate-ciliate, apex acute to acuminate, base deeply cordate, lobes sometimes slightly imbricate, inconspicuously overlapping the petiole, venation actinodromous, veins 6–8. Inflorescence reduced thyrsoids, 30–48 cm tall, bearing 10–20 (–26) flowers, paraclades usually 2, rarely 3; peduncles (16–) 18.5–41.5 cm long, reddish, rachis puberulous, trichomes simple and glandular microscopic, bracts persistent, rarely deciduous, broadly elliptic to elliptic, white to pink, 6–12 mm long, margins ciliate with glandular trichomes, apex acute to obtuse, abaxial surface with microscopic glandular trichomes. Male flowers 15–20 mm long, pedicels (6–) 10–15 mm long, pink, short glandular trichomes; tepals usually 4, rarely 5, white, external pair, orbicular, broadly ovate, broadly elliptic to broadly obovate, 7–13 × 8–12 mm, abaxial surface with microscopic glandular trichomes, margins entire to ciliate, apex acute, or obtuse to rounded, base rounded, inner tepals usually 2, rarely 3, elliptic to obovate, 7–14 × 3–5 mm, glabrous or with diminutive glandular trichomes, margins entire to denticulate, apex obtuse to acute, base acute, stamens 46–82, free, 2–3.2 mm long, filaments 0.5–3 mm long, on a conical receptacle, approximately 1 mm long; anthers cordiform, obovoid to broadly obovoid, 0.5–1 mm long, rimose, extrorse, connectives usually not prominently projecting to rarely prominently projecting. Female flowers 20–65 mm long; bracteoles absent; pedicels 6–27 mm long; tepals usually 5, rarely 6, white, cymbiform, elliptic, obovate to broadly elliptic, of unequal size, 1 tepal significantly smaller, 6–7(–11) × 2.5–3 mm, glabrous, margins denticulate, apex and base acute, hypanthium with glandular trichomes, style ca. 0.5 mm long, stigmas 2–3 mm long, branches bifurcate, base flabelliform, 3–lobed or with two horned projections, stigmatic papillae on the branch margins, placentae divided, lamellae unequal, ovules on both faces of the lamellae. Immature capsules 10–15 (–23) × 25–29 (–40) mm, locular region widely elliptic to elliptic, 6–9 mm wide, pericarp papery, larger wing retilinear on the upper margin to slightly recurved towards the apex, inferior margins rounded, 15–20 mm long, smaller wing rounded, 2–3 (–6) mm long, seeds elliptic, 248–266 μm long.

Etymology:—The specific name refers to the preferred environment of the species, a vegetation formation found along the margins of rivers, lakes, and reservoirs, known locally as ciliary forests, gallery forests, or riparian forests.

Phenology: —Flowering from January to May; fruiting from April to May.

Distribution and ecology: —The species is endemic to central Brazil, occurring in the states of Goiás, Mato Grosso, Mato Grosso do Sul, and northwestern Minas Gerais. It grows in dense alluvial ombrophilous forests (gallery forests), sometimes disturbed, on rock outcrops and between larger rocks on forested slopes or on sandy-clayey soils with superficial leaf litter; encountered at elevations near 400 m. During dry periods, the species will lose its aerial portion and re-sprout after the rains. This survival mechanism during dry periods of the year is likewise encountered in other Brazilian species of Begonia , such as B. alchemilloides A. DC. (pers. obs.).

Additional specimens examined (paratypes):— BRAZIL. Goiás: Niquelândia, estrada Niquelândia a Colinas , 14 April 1992, B. M. T. Walter et al. 1284 ( CEN!) ; ib., Serra da Mesa, segmento Rio Bagagem , 13°59´57”S, 48°19´05”W, 30 January 1997, B. M. T. Walter et al. 3708 ( CEN! SP!). Mato Grosso: Chapada dos Guimarães, 26 March 1987, G. Hashimoto 557 ( GHSP!) ; ib., Rancho Paredão da Serra, 24 February 1997, A. G. Nave et al. 1206 ( ESA!). Municipal district uncertain, Rio Garças , 6 May 1958, A. Lima 58-3132 ( K!). Mato Grosso do Sul: Municipal district uncertain, [Rio Taquaraçu] Taquaraussú, Chapada, March 1911, F. C. Hoehne Comissão Rondon ( CR) 3880 ( R!) ; Municipal district uncertain, March 1911, F. C. Hoehne em Comissão Rondon 3881 ( B!). Minas Gerais: Cabeceira Grande, Área de influência da Usina Hidrelétrica de Queimado , 18 February 2003, A. A. Santos & J. B. Pereira 1836 ( CEN!) .

Taxonomic notes:— De Candolle (1864: p. 330, 517) described Begonia novogranatae in his original publication based on material collected by Linden in Nova Granada, Columbia. Smith & Schubert (1946: p. 8) described B. quetamensis likewise based on material collected in Columbia (Pennell 1853 holotype NY!), citing B. inamis Irmsch. (M.T. Dawe 272 holotype US! isotype K!) in synonymy of that species.

In the treatment of the Begoniaceae of Columbia, B. novogranatae and B. quetamensis were recognized as distinct species that differed in terms of length of petioles (5 cm vs. 22–24 cm), leaf attachments (peltate vs. basifixed) and number of pistilate tepals (5 vs. 6) ( Smith & Schubert 1946), although those authors had not analyzed the holotype of B. novogranatae , nor any material similar to that species deposited in Colombian herbaria. Smith & Wasshausen (1984: p. 469) synonymized B. quetamensis under B. novogranatae , thus creating more confusion in terms of the concepts of the taxa. Those authors elected B. novogranatae as the correct name for the species, probably based on the principle of priority under the International Code of Nomenclature for algae, fungi, and plants (Division I, Principles III). Everything indicates, however, that the synonymization was proposed without having examined the holotype of B. novogranatae (Linden s.n.). That classification was accepted by Smith et al. (1986) although, once again, those authors did not make it clear that they had analyzed the holotype of B. novogranatae ; that species is, in fact, represented in their publication (Smith et al. 1986) by an illustration of B. quetamensis .

Although it has not yet been possible to locate the holotype of B. novogranatae (Columbia, Nova Granada, Linden s.n., Herbarium probably BR), the protolog of that species leaves no doubt concerning its identity (principally by the presence of peltate leaves—a diagnostic character for species of Begonia ) being quite distinct from B. quetamensis , which has basifixed leaves. As such, B. quetamensis needs to be re-established as the correct name, distinct from B. novogranatae .

Begonia rivularis is most similar to Begonia quetamensis L.B. Sm. & B.G. Schub. and B. novogranatae A. DC. , although it differs from Begonia quetamensis by having smaller male tepals 7–14 mm long (vs. 17 mm long.) and styles bifurcate (vs. multifidis) and from B. novogranatae by having basifixed leaves (vs. peltate), stigmas with bifid branches (vs. multifids) and larger capsules 10–15 (–23) × 25–29 (–40) mm (vs. 8–10 × 10–12 mm).

Figures

FIGURE 3. A–G. Begonia mamedeana E.L. Jacques. A, Flowering branch; B, Male flower bud; C, Male flower; D, Stamens; E, Female flowers; F, Stigma; G, Fruits. H–M. Begonia rivularis E.L. Jacques (del from R. Lupo). H, Habit; I, Bracts; J, Male flower; K, Stamens; L, Female flowers; M, Stigma. (A, from Furlan 1056; B–F, from Fernandez 109; G, from Jacques 33; H, J–M from Walter 1284; I, from Nave 1206).