Typus: BRAZIL. Espírito Santo: Jaguaré county, Giral, 80 m, 18°49′33.9″S 40°03′32.8″W, 17.I.2009, fl. fr., L. Kollmann & R. S. Lopes 11441 (holo-: MBML!; iso-: CEPEC!, MBM!, P!, RB!, SP!, U!, US!, VIES!).

Begonia jaguarensis is very similar to B. thelmae L. B. Sm. & Wassh., but can be distinguished by longer internodes, ovate to elliptic leaves, smaller stipules with a base deeply and laterally cordate as well as overlapping lobes appearing peltate, smaller sepals and petals in the staminate flower.

Herb terrestrial or epiphytic, sub-erect to repent, 2–16 cm tall, with glands and simple trichomes. Stems 3–5 mm diam., green to brownish, glabrescent, without lenticels, internodes (l-)2.2–4 cm long. Stipules 6–9 × 3–4 mm, greenish, persistent, glabrous on both faces, ovate, apex acute, base asymmetric, oblique, margins fimbriate to ciliate. Petioles 0.6–2 cm, whitish, pilose, trichomes red; lamina (2.6-)4–7.5 × (0.9-)1.5–2.7 cm, adaxial face glossy, green to green with pale veins, abaxial face green to red, when red margins green, simple, asymmetrical, ovate to elliptical, glabrous to hispid, apex acute, base cordate, margins serrate to serrulate, ciliate, venation actinodromous, the mid-nerve following the petiole axis, veins 6–7 at base, adaxial face with hispid central vein, abaxial face lightly hispid on vein, stomata clustered. Inflorescences 3–6 cm long, axillary, monochasial, rarely dichasial, glandular to pilose, monochasial inflorescences 1-few-flowered, (3-)5 staminate flowers, 1 pistillate flower, dichasial inflorescences 2-few-flowered, 7–11 staminate flowers, 2 pistillate flowers, peduncles 2–2.5 cm long, white, bracts 0.5–1.4 × 0.25–0.8 mm, green-whitish, apex reddish, translucent, persistent, ovate to lanceolate, apex acute to acuminate, flower scars prominent in dry material. Staminate flowers: pedicels 6–12 mm long, white, glandular to pilose, sepals 2,4.5–6 × 3–4.5 mm, white, ovate, apex obtuse, petals 2,4–6 × 2.1–2.3 mm, white, elliptic to obovate, apex obtuse, lightly concave; stamens 6–8, yellow, on a short column, filaments ca. 0.5 mm long, anthers ca 2.9 × 0.8 mm, oblong, rimose, extrorse, the connective projecting beyond the anthers, apex obtuse. Pistillate flowers: pedicels 2.5–4 mm long, white, glandular; prophylls 2,0.8–1.5 × 0.3–0.7 mm, green, translucent, ovate to oblong, apex acute, red; sepals 2, 4–4.8 × 2–2.1 mm, white, elliptical, apex acute, petals 3(-4), 3.8–5.2 × 1.2–2.7 mm, white, ovate, apex obtuse to acute; styles 3, ca. 2 mm long, yellow, bifid, united at base, stigma lightly spirally twisted, covered by stigmatic papilla; ovary 3-locular, placentation axile, one placenta per locule, ovules on both sides of placentae. Capsules 0.7–1 × 0.5–0.6 mm, white, glabrous, basally dehiscent; wings 3,0.8–1.5 ×0.2–0.55 cm, glandular, sub-equal, rounded to angular, stigma persistent in dry fruit. Seeds 0.27– 0.3 × 0.15–0.2 mm, cylindrical, oblong.

Taxonomy. — Smith & Wasshausen (1981) placed B. thelmae in Begonia sect. Begonia because one of the three placentae is bifid. Doorenbos et al. (1998) did not include it in any section, indicating that it could belong to a new section. Begonia jaguarensis and B. thelmae appear more closely related to sect. Pritzelia (Klotzsch) A. DC. due to the presence of a single placenta per locule with ovules on both sides of the placenta and extended anther connectives, but the two specie appear related also to sect. Doratometra (Klotzsch) A. DC. by the small inflorescence, dichasial to monochasial, few-flowered, with persistent bracts, stamens on a short column, and pistillate flower with prophylls.

Relationships. — Begonia jaguarensis resembles B. thelmae from northern Espírito Santo, in its creeping habit, fimbriate and persistent stipules, axillary inflorescences that are erect, monochasial, exceptionally dichasial, and few-flowered, and male flowers with few stamens. It can be distinguished from B. thelmae by its longer internodes 2.2–4 (vs. 1–2) cm, ovate to elliptic leaves (vs. elliptic to obovate), apex acute (vs. obtuse), smaller stipules (0.65–0.8 vs. 1–1.5 cm long), a stipule base deeply and laterally cordate with overlapping lobes appearing peltate (vs. asymmetric base, not cordate and not appearing peltate), staminate flower with smaller sepals and petals (4–6 vs. 7–9 mm long), and 2 prophylls (vs. 1) (Table 1).

Observations. — The original description of Begonia thelmae by Smith & Wasshausen (1981) stated that the ovary had two simple placentae and one bifurcate placenta with ovules on both side. Tebbitt (2005), however, wrote that the three placentae are entire. Studies of live plant from the “Conservatoire du Begonia, Rochefort, France”, and from the United States of America, showed three entire placentae (L. Kollmann, unpubl. data). It is possible that a variation of placentation occurs in some cultivated plant of the USA, a phenomenon that is not rare in Begonia. The authors of B. thelmae wrote “deciduous bracts on swollen persistent bases”, but when studying the plant, we observed persistent bracts and what appeared as swollen persistent bases were the bases of staminate flowers and not of bracts, as reported in the description. Begonia thelmae was introduced into the USA in 1974 by Gil Daniels from the collection of Burle Marx, Rio de Janeiro, Brazil and published as a new species by Smith & Wasshausen (1981) (holotype US-2639955).

In the Rio de Janeiro Botanical Garden Herbarium (RB) a voucher of B. thelmae exists, collected by A. P. Duarte (in 1979) at the locality Serra de Cima, Nova Venécia county, north of Espírito Santo State, Brazil.

Etymology. — The specific epithet alludes to the Jaguaré county, where the holotype of the new species was first found.

Distribution and ecology. — Begonia jaguarensis was found growing in leaf litter in “muçununga” forest of “tabuleiro” (tableland), in northern Espírito Santo state, between 30–150 m (Fig. 2, 3), within the Central Corridor of the Atlantic Forest domain. Peixoto & Silva (1997) included the “tabuleiro” forests of northern Espírito Santo as one of Brazil's 14 centers of plant diversity. The “muçununga” forest is characterized by humid, sandy porous soils. The trees in the upper stratum vary in height between 7–10 m (Simonelli et al., 2008), with herbaceous plants like Calathea sp. (Marantaceae), Dichorisandra thyrsiflora J. C. Mikan (Commelinaceae), Anthurium sp. (Araceae), Sinningia richii Clayberg (Gesneriaceae), Bromelia antiacantha Bertol., and Cryptanthus beuckeri E. Morren (Bromeliaceae). Begonia jaguarensis is a very distinctive species in its creeping habit. Its forms “carpet” that can reach about 3 square meter; the stems are creeping, densely jointed, covering the entire floor, and readily rooting on contact with the soil, in semi shaded place (Kollmann 11441) (Fig. 2B, C). The paratype (Kollmann 11418) (Fig. 2D), was found growing in a sunlit, disturbed habitat of a little waterfall, the plants being small with a few bicolor leaves. The others paratypes were found growing in the Sooretama Biological Reserve and Vale Natural Reserve, 20 to 30 kilometers from the holotype. Flowers have been collected between January and June and fruits from January to August.

Conservation status. — Given the distribution of B. jaguarensis, with an extent of occurrence estimated to be less than 100 km² and continuing decline of area, extent and quality of habitat and growing in two Conservation Units (Fig. 3), it seems appropriate to include this species in the Critically Endangered Category [CR B1+B2b(iii)] according to the IUCN red list criteria (IUCN, 2001).

Paratypi. — Brazil. Espírito Santo: Jaguaré, Reserve Biológica de Sooretama, Lagoa do Macaco, 30 m, 15.V.1977, fl., fr., Martinelli et al. 2212 (RB!); ibid, loc., Lagoa do Macaco, 30 m, 15.V.1977, fl., fr., Martinelli et al. 2139 (RB!); Giral, 16.I.2009, fl., fr., L. Kollmann & R. Lopes 11418 (MBML!); Linhares, Reserva Natural Vale, estrada Aderne, 24.III.2004, fl., fr., D. A. Folli 4780 (CVRD!, MBML!); ibid, loc., Estrada Gávea, 5.IV.2002, fl., fr., D. A. Folli 4227 (CVRD!, MBML!); ibid, loc., Estrada da Gávea, km 23.4, 30.III.2011, fl., fr., L. Kollmann et al. 12233 (MBML!, CVRD!); Sooretama, Reserva Biologica de Sooretama, mata de tabuleiro do Macuco, 17.VII.1969, fr., D. Sucre 5708 (RB!); ibid, loc., matas de Quirino, 60–100 m, 12.V.1985, fl., fr., G. Martinelli et al. 10968 (RB!, INPA!, NY!).