Begonia subvillosa Klotzsch, 1854

Moonlight, Peter & Fuentes, Alfredo F., 2022, AN UPDATED CHECKLIST AND KEY TO THE SPECIES OF BOLIVIAN BEGONIA, INCLUDING ONE NEW SPECIES, Edinburgh Journal of Botany 79 (407), pp. 1-66 : 26-29

3.19. Begonia subvillosa Klotzsch , Abh. Kon. Akad. Wiss. Berlin 1854: 152, (1855).

– Type: Brazil, sine loc., von Sello 1571 (lectotype B [ B10024925 , photograph F#20903 ] designated here, first stage designated in: Abh. Kon. Akad. Wiss. Berlin 1854: 151, (1855) by Irmscher, E.; isolectotype B [2: B10024924 , B10024926 ) .

A.P. de Candolle, Fl. Bras. 4: 344 (1861); A.P de Candolle, Prodr. 15(1): 304 (1864); L.B. Smith & B.G. Schubert, Revista Univ. (Cuzco) 33(87): 79 (1944); R.C. Foster, Contr. Gray Herb. 184: 138 (1958); E.L. Jacques & M.C.H. Mamede, Revista Brasil Bot. 28(3): 584 (2005).

Begonia lindmanii auct. non. Brade, D.C. Wasshausen et al . in P.M. JØrgensen et al. (eds), Cat. Bolivia, Monogr. Syst. Bot. Missouri Bot. Gard. 129: 385 (2013).

Caulescent herb, lacking a tuber or rhizome but sometimes with a swollen, tuber-like base to the stem, 10–40 × 12–40 mm, rooting from the lower nodes. Stem erect, 10–30 cm tall, 1.5–5 mm in diameter, branching, internodes 5–10(–42) mm, densely villous, red. Stipules persistent, triangular to broadly ovate, 5–10 × 3–7 mm, apex obtuse, mucronate, glabrous to densely villous, light brown, margin lacerate, long-ciliate. Leaves alternate, basifixed; petioles joining blade at a right angle, 5–35 mm long, densely villous; blades asymmetrical, transversely ovate, 40–65(–120) × 25–40(–65) mm, apex obtuse to acuminate, base cordate, basal lobes to 8 mm, not overlapping the petiole, venation palmate, 7–9 veins from the base, upper surface dark green, sparsely pilose, lower surface deep red, densely villous, margin irregularly dentate, ciliate. Inflorescences 1–3 per stem, axillary, erect to pendulous, arising close to the apex of the stem, a dichasial cyme, protandrous, with up to 8 staminate flowers and 8 pistillate flowers; peduncle 35–45 mm long, sparsely villous, pink to red; pedicels of staminate flowers 5–8 mm long, glabrous to sparsely villous, pink to red; pedicels of pistillate flowers 5–10 mm long, sparsely villous, pink; bracts persistent, elliptic to ovate, 1.5–5 × 1–2 mm, apex acute to rounded, pale pink, glabrous, margin lacerate, ciliate. Staminate flowers: tepals 4, spreading, white, sometimes flushed pink outside, the inner two oblanceolate, 4–9 × 2–5 mm, apex rounded, base narrowly cuneate, margin entire, glabrous, the outer two orbicular, 5–9 × 5–10 mm, apex rounded, margin entire, glabrous; stamens 8–12, fused at the base, spreading, filaments 0.25–1 mm long, anthers symmetrically basifixed, oblong, 1.5–2 mm long, dehiscing via lateral slits, connectives extended c. 0.2 mm. Pistillate flowers: bracteoles 3, persistent, oblanceolate, 5–9 × 1.5–3.5 mm, apex obtuse, pink, glabrous, margin lacerate, ciliate; tepals tardily deciduous in fruit, 5, spreading, oblanceolate, 6.5–10 × 2–6 mm, apex acute to rounded or emarginate, margin entire, aciliate, glabrous, white with a pink flush on outer surfaces; ovary body ovoid, 6–12 × 4–6 mm, green or white flushed pink, 3-winged, wings pink, one wing longer than the other two, triangular, ascending, front edge truncate, apex acute, lower edge rounded, 7–13 × 6–13 mm, the shorter two wings semicircular to triangular, front edge truncate, apex rounded, lower edge gently curved, 7–12 × 5–6 mm, 3-locular, placentas bifid, bearing ovules on both surfaces; styles 3, yellow, free at base, bifid from around half their length, stigmatic papillae in a spirally twisted band. Fruiting pedicel to 12 cm long; fruit held erect, body ovoid, 8–12 × 6–8 mm, light brown, glabrous, wings same shape as in pistillate flower, light brown, longest wing expanding to 15 × 13 mm, shorter two wings expanding to 14 × 7 mm.

Distribution and ecology. Begonia subvillosa is known with certainty from Brazil (Rio Grande do Sul State) and Bolivia. It has been identified from herbarium specimens from Paraguay; however, we have not seen any such specimens so have been unable to confirm these identifications as part of the present study. Within Bolivia, Begonia subvillosa is known from two localities, approximately 55 km apart, in Chiquitos Province of Bolivia: the Cerro Chochís and the Serranía de Santiago. Together, these form a 120 km long, almost continuous northwest–southeast ridge, which is highest in the north. The species has mostly been collected growing from crevices in exposed sandstone ridges on the highest parts of the ridge, but one collection (H. Cutler 7060) may have been collected growing on rocks in gallery forest on the southwest side of the ridge. Begonia subvillosa often has a swollen, hardened stem at the base and may die back to these stems each dry season. It has been collected in flower and fruit from January to April.

Etymology. The epithet refers to the sparsely to densely villous indumentum found over most of the stems and leaves in this species.

Proposed IUCN conservation category. Within Bolivia, Begonia subvillosa is known from two localities in the Serranías Chiquitanas. These populations are disjunct from the only other confirmed localities in Brazil. The species’ known EOO is> 216,000 km 2, but its known area of occupancy is significantly smaller (40 km 2). The Serranías Chiquitanas remain relatively pristine but may in the future be threatened by mining, which is common on similar geological features in Brazil. A second potential threat is wildfires, which are an increasing threat in lowland Bolivia and has affected granitic outcrops northwest of the Serranías Chiquitanas. The Serranías are sandstone, and their relative topographical complexity compared with granitic outcrops may afford some protection against fire ingress. Finally, the incidence of drought in the area has increased markedly since 2010 ( Maillard et al., 2019). Within Bolivia, the species has an EOO of <50 km 2, so we assess the Bolivian population of Begonia subvillosa as Critically Endangered (CR), B2ab(iii), under IUCN criteria ( IUCN Standards and Petitions Subcommittee, 2019).

Additional specimens examined. BOLIVIA. Santa Cruz Department. Chiquitos Province: Cerro Chochís , on the meseta at the summit, [18°7′S, 60°0′W], 1200 m, 22 ii 2006, J.R.I. Wood 22239 ( K) ; On ascent from top of pass on Santiago de Chiquitos to Susas road , to serrania immediately E of road , [18°20′S, 59°34′W], 650 m, 1 iv 2002, J.R.I. Wood 18003 ( K, LPB) ; North slope of Serrania de Santiago , 10 km ENE of Santiago de Chiquitos, c. 18°20′S, 59°28′W, 900 m, 21 vii 1983, D.C. Daly, M.J.G. Hopkins, L.E. Forero, S. Beck, N. Hernandez, H. Phipps III & H. Wolf 2234 ( NY) ; 2 km northwest of Santiago, [18°19′S, 59°37′W], 630 m, 10 ix 1942, H.C. Cutler 7060 ( GH) ; Serrania de Santiago de Chiquitos , E of pass on road to Sunsás , [18°20′S, 59°34′W], 850 m, 25 i 2001, J.R.I. Wood & D.J. Goyder 16955 (K) ; cerca de la cumbre de las serranías de Santiago , 18°20′47′′S, 59°33′44′′W, 803 m, 10 iv 2008, J.R.I. Wood, N. Hind, P. Pozo & D. Villarroel 24361 ( K [ K000374263 ], LPB) ; Santiago de Chiquitos , subida a el Mirador de la Serranía de Santiago de Chiquitos , sobre el camino a Santo Corazón , 18.3226°S, 59.5716°W, 846 m, 21 iii 2009, J.R.I. Wood, D. Villarroel & S. Renvoize 25847 (holotype K [ K00374265 ], LPB) .

Notes. Begonia subvillosa is a member of Begonia sect. Ephemera and is most similar to B. leptotricha C.DC. Begonia leptotricha is treated as a synonym of B. subvillosa by the most recent floras of Brazil ( Brazil Flora Group, 2015) and Argentina ( Delfini, 2017), following Jacques & Mamede (2005). We instead follow Irmscher (1953) and Jaramillo (2017) in recognising Begonia leptotricha as a distinct taxon.

The two species are best determined by their leaf margins (serrate in Begonia subvillosa , entire to crenate in B. leptotricha ) and their leaf indumentum. The indumentum of Begonia subvillosa is persistent, pilose on the upper leaf surfaces and densely villous on the lower surfaces, whereas both leaf surfaces of B. leptotricha are densely arachnoid, easily rubbing off in patches.

Nomenclatural notes. In the protologue of Begonia subvillosa, Klotzsch cited material collected by von Sello in Brazil but did not cite any herbaria. Irmscher (1953) cited material in Berlin herbarium as the type; however, because there are three sheets in Berlin, this effected only the first stage of lectotypification. Jacques & Mamede (2005) incorrectly cited material in Berlin as the holotype, but this was incorrect because there is no holotype. We choose the sheet B10024925 as the lectotype of Begonia subvillosa , partially because this is the best of the three sheets in Berlin herbarium and partially because this sheet was photographed by staff of the Field Museum in the 1920s and has therefore served as a de facto type ever since.

Identification notes. Within Bolivia, Begonia subvillosa is most likely to be confused with B. alchemilloides . Both species are delicate herbs that grow in crevices in rock outcrops in the Bolivian lowlands and die back in the dry season to a perennial, swollen stem base. Begonia subvillosa is best distinguished by its transversely ovate leaves (vs reniform in B. alchemilloides ) and its much larger staminate (up to 20 mm across vs 12 mm across) and pistillate flowers (15 mm across vs 11 mm across). Begonia subvillosa also differs in its densely villous stems, petioles, and lower leaf laminae, which contrast with the glabrous to sparsely villous stems, petioles, and lower leaf laminae of B. alchemilloides .