Neotropical Commelinaceae

Lidyanne Yuriko Saleme Aona

Universidade Federal do Recôncavo da Bahia (UFRB), Brazil. 

Description

Annual or perennial herbs, generally terrestrial and somewhat fleshy or succulent, when perennial with rhizomes or stolons; stems clearly divided into nodes and internodes, simple or branched, sometimes rooting from the stem; roots fibrous, fine or tuberous. Leaves simple, alternate, distichous or spiral, sometimes as basal rosettes, generally sessile, petiolate, if present then not inflated; sheath closed, glabrous, villose to densely hairy, margin generally ciliate. Inflorescence terminal and/or axillary or basal, with few to many unilateral cymes aggregated in thyrses, flowers subtended by foliaceous bracts or enveloped by spathaceous bracts. Flowers hermaphroditic, sometimes hermaphroditic and male, rarely cleistogamous, trimerous with radial or bilateral symmetry; perianth separated into sepals and petals, sepals 3 free, imbricate; petals 3, usually free, often disintegrating easily; stamens 6 in two series, sometimes 1-4, modified into staminodes or suppressed in some genera, filaments free or epipetalous, frequently hairy, anthers basifixed or dorsifixed, sometimes versatile, with longitudinal or poricidal dehiscence; ovary superior, (2-)3-locular, placentation axile, ovules 1 to many per locule, septal nectaries absent, style simple, stigma punctiform or capitate, rarely penicillate. Fruits loculicidal capsules, 2-3-valvate, rarely indehiscent, baccaceous and sometimes crowned by fleshy sepals; seeds normally without aril, hilum linear to punctual, embryo covered by a callous tissue (embryotegium), testa smooth or ornamented.

Notes on delimitation

  • Molecular studies have shown that Commelinaceae are included in the order Commelinales together with Haemodoraceae, Hanguanaceae, Philydraceae and Pontederiaceae (APG II, 2003), with the Pontederiaceae as the nearest family to Commelinaceae.

Distribution in the Neotropics

  • Aneilema R.Br. (Panama, Peru and Brazil, c. 2 species).
  •  Buforrestia C.B.Clarke (tropical South America, c. 3 species).
  • Callisia Loefl. (tropical America, c. 20 species).
  • Cochliostema Lem. (Nicaragua to Ecuador, 2 species).
  • Commelina L. (Over 40 species in tropical America).
  • Dichorisandra J.C.Mikan (tropical America, mainly in Brazil, c. 65 species).
  • Elasis D.R.Hunt (Ecuador, 1 species).
  • Floscopa Lour. (tropical America, c. 2 species).
  • Geogenanthus Ule (tropical South America, 5 species).
  • Gibasis Raf. (México to Argentina, c. 11 species).
  • Gibasoides D.R.Hunt (Mexico, 16 species).
  • Matudanthus D.R.Hunt (Mexico, 1 species).
  • Murdannia Royle (Introduced to the Neotropics where it has c. 3 species).
  • Plowmanianthus Faden & C.R.Hardy (Panama, Peru and Brazil, 5 species).
  • Pollia Thunb. (Panama, 1 species).
  • Siderasis Raf. (tropical South America, c. 3 species). Thyrsanthemum
  • Pichon (Mexico, 3 species).
  • Tinantia Scheidw. (Mexico to Argentina, 13 species).
  • Tradescantia L. (Over 60 species in tropical America).
  • Tripogandra Raf. (tropical America, c. 22 species).
  • Weldenia Schult.f. (Mexico to Guatemala, 1 species).

Distinguishing characters (always present)

  • Leaves with closed sheaths that may be involute in bud.
  • Leaves alternate, distichously or spirally arranged, sometimes in basal rosettes.
  • Inflorescences terminal and also axillary or basal, with unilateral cymes.
  • Sepals and petals 3, clearly distinguishable, petals sometimes disintegrating.

Other important characters

  • Usually fleshy or succulent herbs.
  • The filaments are often conspicuously hairy.

Key differences from similar families

Differs from:

  • Pontederiaceae, which are aquatic and floating or immersed and have inflated petioles.
  • Haemodoraceae, where perianth whorls are fused basally and septal nectaries are present.

Useful tips for generic identification

  • Faden and Hunt (1991) accepted 2 subfamilies: Cartonematoideae (raphide canals absent or next to the leaf veins), which was divided into 2 tribes: Cartonemateae and Tricerateleeae; and Commelinoideae (raphide canals present and mostly between leaf veins, etc), also comprising 2 tribes: Tradescantieae and Commelineae.
  • To identify the genera it is important to observe flower characters in the field, e.g.the colour and shape of the petals, and the number of stamens, their disposition and the dehiscence of the anthers.
  • The plant habit is also important and may vary between rosulate, rhizomatous or stoloniferous, trailing plants, and erect or semi-scandent herbs to 4 m tall.

Notable genera and distinguishing features

Dichorisandra:

  • Anther dehiscence always poricidal, but functionally poricidal anthers with an introrse longitudinal slit are also found.

Status

  • Most genera cited here are native to the Neotropics.
  • Only Murdannia has species introduced from the Old World.
  • Species of Dichorisandra, Tradescantia and Gibasis geniculata (Jacq.) Rohweder are used as ornamentals.
  • Several species of Commelina are weedy.

Important literature

AONA, L.Y.S. 2008. Revisão taxonômica e análise cladística do gênero Dichorisandra J.C. Mikan (Commelinaceae). Tese de doutorado. Instituto de Biologia, Universidade Estadual de Campinas, Campinas.

AONA, L.Y.S. & LEONI, L.S. 2006. Flora Fanerogâmica do Parque Estadual do Brigadeiro: Commelinaceae. Pabstia XVII(3):1-10.

APG II (2003). An update of the Angiosperm Phylogeny group classification for the orders and families of flowering plants: APG II. Botanical Journal of the Linnean Society 141(4): 399-436.

BARRETO, R.C. 1997. Levantamento das espécies de Commelinaceae R. Br. nativas do Brasil. Tese de doutoramento. Instituto de Biociências, Universidade de São Paulo, São Paulo.

FADEN, R.B. & Hunt, D.R. 1991. The classification of the Commelinaceae. Taxon 40:19-31.

FADEN, R.B. 1998. Commelinaceae. In: K. Kubitzki (ed.) The Families and Genera of Vascular plants 4: 109-128. Springer Verlag. Berlin.

HARDY, C.R. & FADEN, R.B. 2004. Plowmanianthus, a new genus of Commelinaceae with five new species from Tropical America. Systematic Botany 29(2):316-333.

How to cite

Aona, L.Y.S. (2009). Neotropical Commelinaceae. In: Milliken, W., Klitgård, B. & Baracat, A. (2009 onwards), Neotropikey - Interactive key and information resources for flowering plants of the Neotropics. http://www.kew.org/science/tropamerica/neotropikey/families/Commelinaceae.htm.