Neotropical Cyperaceae

Ana Paula do Nascimento Prata* and David A. Simpson**

*Universidade Federal de Sergipe, Brazil.**Royal Botanic Gardens, Kew, U.K. 

Description

Perennial or annual herbs, terrestrial, rarely submerged aquatics, or scandent; perennial species rhizomatous, stoloniferous, bulbous, or subbulbous; annual species generally caespitose. Some genera have a caudex (e.g. Bulbostylis). Culms usually trigonous to triquetrous, less often terete, flattened or irregular, formed by prominent ribs. Leaves basal or basal and cauline, generally tristichous with a closed sheath; blade usually linear, glabrous, scabrous, hairy, hispid, with central midrib prominent, sometimes with an expanded, 3-veined blade (Hypolytrum, Mapania); ligules usually absent (but present in Scleria, Fimbristylis, Fuirena and Carex).  Involucral bracts usually present, leaf-like or glume-like. Inflorescence simple to compound, lax to condensed and usually highly branched, paniculate, corymbose, spicate, or capitate, comprising 1 to many ultimate inflorescence units, these either indeterminate (= spikelets) or, in a few genera, determinate (= spicoids). Spikelets few to many, sometimes reduced to a single spikelet (Eleocharis), terminal or lateral comprising 1-many scales, usually spirally arranged, or sometimes distichous; flowers bisexual, unisexual, or both types present; spicoids few to many, terminal, with 2-12 membranous scales on a much reduced axis, the lowest 2 scales opposite, keeled, the spicoid subtended and usually hidden by a larger scale-like bract; flowers unisexual. Perianth absent or of 1-many bristles or scales. Stamens 1-3. Ovary superior, carpels usually 2-3, locule 1, ovule 1; style short to elongate, base thickened and sometimes persistent; stigma usually 2-3-branched. Fruit a nutlet, nutlet-like or a nutlet protected by a utricle.

Notes on delimitation

  • Because of their great morphological similarity, Cyperaceae and Poaceae were, for a long time, considered to be closely related families. DNA studies have shown that Juncaceae (along with Thurniaceae) are the sister group of Cyperaceae, rather than Poaceae.
  • Cyperaceae are divided into two subfamilies (Simpson et al. 2007): Cyperoideae and Mapanioideae: Cyperoideae - the most diverse subfamily.  Members of this subfamily have spikelet-type inflorescence units with unisexual or biesexual flowers (Androtrichum, Ascolepis, Becquerelia, Bisboeckelera, Bulbostylis, Calyptrocarya, Carex, Cephalocarpus, Cladium, Cyperus, Didimiandrum, Diplacrum, Egleria, Eleocharis, Everardia, Exochogyne, Fimbristylis, Fuirena, Kyllinga, Lagenocarpus, Lipocarpha, Oreobolus, Pleurostachys, Remirea, Rhynchospora, Scirpus, Scleria, Trilepis, Uncinia); and Mapanioideae - members of this subfamily have spicoid-type inflorescence units with unisexual flowers. Many species occur in the herb layer of tropical rainforests (e.g. the Amazonian and Atlantic coastal forests) (Diplasia, Hypolytrum and Mapania).

Distribution in the Neotropics

  • Cyperaceae have high species diversity in the Neotropics. Of the 5,400 species described in 106 genera (Govaerts et al. 2007), 43 genera and approximately 1,000 species occur in the Neotropics. Brazil has 622 species in 43 genera (Alves et al. 2007).

Distinguishing characters (always present)

Other important characters

  • Tristichous leaves.
  • Ligule.
  • Silica.
  • Persistent style base (stylopodium) in some genera (Bulbostylis, Eleocharis, Rhynchospora).

Key differences from similar families

Cyperaceae are sometimes confused with Poaceae and Juncaceae.  These, however, differ from Cyperaceae in the following characters:

Number of genera

43 genera and approximately 1,000 species.  Larger genera in Neotropics: Rhynchospora (250 spp.), Carex (200 spp.), Cyperus (150 spp.), Bulbostylis (70 spp.), Eleocharis (60 spp.) and Scleria (60 spp.).

  • Abildgaardia Vahl
  • Androtrichum (Brongn.) Brongn.
  • Ascolepis Nees ex Steud.
  • Becquerelia Brongn.
  • Bisboeckelera Kuntze
  • Bolboschoenus (Asch.) Palla
  • Bulbostylis Kunth
  • Calyptrocarya Nees
  • Carex L.
  • Cephalocarpus Nees
  • Cladium P. Browne
  • Cryptangium Schrad. ex. Nees
  • Cyperus L.
  • Diplacrum R. Br.
  • Diplasia Rich.
  • Egleria Eiten
  • Eleocharis R. Br.
  • Everardia Ridl. ex Thurn.
  • Exochogyne C.B. Clarke
  • Fimbristylis Vahl
  • Fuirena Rottb.
  • Hypolytrum Rich.
  • Isolepis R. Br.
  • Koyamaea W. Thomas & Davidse.
  • Kyllinga Rottb.
  • Lagenocarpus Nees
  • Lipocarpha R. Br.
  • Mapania Aubl.
  • Machaerina Vahl.
  • Oreobolus R. Br
  • Oxycaryum Nees
  • Pleurostachys Brongn.
  • Pycreus P. Beauv.
  • Remirea Aubl.
  • Rhynchocladium T. Koyama
  • Rhynchospora Vahl
  • Schoenoplectus (Reichb.) Palla
  • Schoenus L.
  • Scirpus L.
  • Scleria P. Bergius
  • Trilepis Nees
  • Uncinia Pers.
  • Websteria S.H. Wright

Useful tips for generic identification

Status

Native.

General notes

  • Cosmopolitan, occupying diverse habitats, with a preference for open and wetland environments. The third largest family of monocotyledons and the seventh largest in the Angiosperms.

Important literature

Alves, M., Araújo, A.C, Prata, A.P, Vitta, F., Hefler, S., Trevisan, R., Gil, A.B., Martins & S.,Thomas, W.W. 2007. Diversidade de Cyperaceae no Brasil. In: A Botânica no Brasil: pesquisa, ensino e políticas públicas ambientais (L. Barbosa & N. Santos Junior, orgs.). SBB, São Paulo, pp. 286-290.

Bruhl, J.J. 1995. Sedge genera of the world: relationships and a new classification of the Cyperaceae. Australian Systematic Botany 8(2): 125-305.

Govaerts, R., Simpson, D.A., Bruhl, J., Egorova, T., Goetghebeur, P., & Wilson, K. 2007. Word checklist of Cyperaceae Sedges. Royal Botanic Gardens, Kew.

Kearns, D.M., Thomas, W.W., Tucker, G., Kral, R., Camelbeke, K., Simpson, D.A., Reznicek, A., González-Elizondo, M., Strong, M. & Goetghebeur, P. 1998. Cyperaceae In: Berry, P.E., Yatskievych, K. and Holst, B.K. (eds.), Flora of the Venezuelan Guayana vol. 4, pp. 486-663. Missouri Botanical Garden, Press, St. Louis.

Simpson, D.A., Muasya, A.M., Alves, M., Bruhl, J.J., Dhooge, S., Chase, M.W., Furness, C.A., Ghamkhar, K., Goetghebeur, P., Hodkinson, T.R., Marchant, A.D., Reznicek, A.A., Nieuwborg, R., Roalson, E.A., Smets, E., Starr, J.R., Thomas, W.W., Wilson, K.L., Zhang, X. 2007. Phylogeny of Cyperaceae based on DNA sequence data - a new rbcL analysis. Aliso 23: 72-83.

Thomas, W.W. 2004. Cyperaceae. In: Smith, N., Mori, S.A., Henderson, A., Stevenson, D.W. & Heald, S.V. (eds.), Flowering Plants of the Neotropics, pp. 434-436. Princeton Univ. Press, Princeton.

How to cite

Prata, A.P.N. & Simpson, D.A. (2009). Neotropical Cyperaceae. 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/Cyperaceae.htm.