Neotropical Begoniaceae

Description

Annual or perennial herbs, shrubs or subshrubs, frequently succulent, erect or climbing, rarely epiphytic; stems erect or creeping, with rhizomes or tubers, generally fleshy. Leaves alternate, simple, entire or lobed, margins serrate, asymmetric, venation palmate or pinnate; petiolate, with caducous or persistent stipules. Inflorescences cymous or thyrsoid. Flowers unisexual (plants monoecious or dioecious), white, pink or reddish. Pistillate flowers slightly zygomorphic, tepals (2-)3-5(6-8) in one whorl, ovary inferior, carpels (1-2)3(4-6), locules (1-2)3(4-6), 1-3(-6)-winged, placentation axile or parietal, placentae bilamellate or entire, styles usually 3, often twisted, united at the base, apically free, stigmas usually 3. Staminate flowers actinomorphic, tepals 2-4(-8) in two whorls, stamens usually numerous, filaments free or fused, anthers with two thecae, dehiscence by longitudinal slits or pores, the connective usually extended beyond the thecae. Fruits usually loculicidal capsules, frequently chartaceous, the mesocarp rarely mucilagionous (Begonia salesopolensis S.J.Gomes da Silva & Mamede), rarely a berry, wings well-developed or rudimentary, seeds numerous, small (235-)300-600(-1450) µm, with a collar of cells at the microphylar-hilar end, testa brown, ornamented, endosperm absent or if present then represented by a single cell layer, embryo erect, cystoliths sometimes present. 2n = 22, 24, 26, 32, 34, 38, 42 and 48.

Distribution in the Neotropics

Begonia L.:

• Mexico
• Central America
• Antilles
• Colombia
• Venezuela
• Trinidad-Tobago
• Guyana
• Suriname
• French Guiana
• Ecuador
• Peru
• Bolivia
• Brazil

(Steyermark, 1997)

Distinguishing characters (always present)

The Begoniaceae can be characterized by:

• An often asymmetric leaf shape.
• Inferior ovary with axile  placentation.
• Bifid style.
• Dry three-winged fruit.
• Seeds with a lid and collar cells.

Other important characters

• Begonia species typically inhabit moist and cloud forest habitats.
• Succulent herbs.
• Leaf base one side much broader than the other.
• Four staminate tepals and five pistillate tepals.  
• One large capsule wing.

Key differences from similar families

• In Datiscaceae fruits dehisce between the styles, pistillate flower tepals are absent in Datiscaceae.
• In Begoniaceae fruits dehisce between the wings, pistillate flower tepals (2-)3-5(6-8), never absent.

Number of genera

• Begonia (1).

Useful tips for generic identification

Begonia:

• Inferior ovary.
• Completely closed ovary.
• Fruits dehisce between the wings.
• (2-)3-5 (6-8) pistillate flower tepals.

Notable genera and distinguishing features

Begonia can be characterized by:

• Often asymmetric leaf shape.
• Four staminate tepals and five pistillate tepals.
• Inferior ovary with axile placentation.
• Dry three-winged fruit.
• Seeds with a lid and collar cells.

Status

• Native.

General notes

• Begoniaceae includes the monotypic genus Hillebrandia, distinguished by a semi-inferior ovary, incompletely closed ovary, fruits that dehisce between the styles, and more numerous, more highly differentiated sepals and petals. It is the only member of the family native to the Hawaiian archipelago (Forrest et al. 2005). 
• The genus Begonia L. (Begoniaceae) has approximately 1,400 named species largely distributed in the tropical and subtropical areas of the world, and within this area is absent only from Australia and Polynesia. It is well represented in Brazil, with approximately 200 species, in almost all ecosystems, except in the mangroves. In Brazil, one of the centers of distribution of the genus is the Atlantic rain forest (Gomes da Silva & Mamede, 2000; Jacques, 1996; Jacques & Mamede, 2004).

Important literature

De Candolle, A. 1861. Begoniaceae. In  Flora brasiliensis (C.P.F. Martius, ed.). F. Fleischer, Leipzig, v. 3, pars. 1, p. 338-396.

Forrest, L.L. & Hollingsworth, P.M.  2003. A recircumscription of Begonia based on nuclear ribosomal sequences. Plant Systematic and Evolution 241: 193-211.

Forrest, L.L.; Hughes, M. & Hollingsworth, P.M. 2005. A phylogeny of Begonia using nuclear ribosomal sequence data and morphological characters. Systematic of Botany. 30(3): 671-682.

Gomes da Silva, S.J. & Mamede, M.C.H. 2000. A new species of Begonia (Begoniaceae) from the Atlantic Coastal Forest in the State of São Paulo, Brazil. Novon 10: 22-25.

Irmscher, E. Begoniaceae. In (A. Engler & K. Prantl, eds.) Die natürlichen Pflanzenfamilien. 2 ed. v. 21, p. 548-588.

Jacques, E.L. 1996. Begoniaceae. In: Lima, M.P.M. & Guedes-Bruni, R.R. (eds.). Reserva Ecológica de Macaé de Cima, Nova Friburgo, RJ - Aspectos Florísticos das Espécies Vasculares - Volume 2: 93-133. Jardim Botânico do Rio de Janeiro, Rio de Janeiro.

Jacques, E.L. 2002. Estudos taxonômicos das espécies brasileiras do gênero Begonia L. (Begoniaceae) com placenta partida. Tese de Doutorado. Instituto de Biociências. Universidade de São Paulo.

Jacques, E.L. & Mamede, M.C.H. 2004. Novelties in Begonia (Begoniaceae) from the coastal forests of Brazil. Brittonia 56(1): 75-81.

Jacques, E.L. & Mamede, M.C.H. 2005. Notas nomenclaturais em L. (Begoniaceae) Revista Brasileira de Botânica 28: 579-588.

Steyermark, J.A.  1997. Begoniaceae in Flora of Venezuelan Guayana. v. 3: p. 397-403.

Warburg, O. 1894. Begoniaceae. In (A. Engler & K. Prantl, eds.) Die natürlichen Pflanzenfamilien. Leipzig: Wilhelm Engelmann, v. 3, n. 6a, p. 121-150.