Neotropical Limnocharitaceae

Emerson Ricardo Pansarin

Universidade de São Paulo, FFCLRP, São Paulo, Brazil. 

Description

Perennial, laticiferous and glabrous aquatic herbs growing in fresh water; hermaphrodite. Roots fibrous, sometimes adventitious. Stems short, sometimes fleshy, rhizomes or stolons present. Leaves basal or alternate, petiolate, simple, sheathing at base, emergent or more rarely submerged or sometimes with floating blade; petiole terete to triangular; blade orbicular to lanceolate with entire margins and reticulate venation; apex obtuse to rounded-acute, with an apical hydathode; base cordate to attenuate. Inflorescence scapose, umbellate, generally erect, emergent or floating; bracts elliptic to acuminate, erect, membranaceous, much shorter than pedicel. Flowers hermaphrodite, actinomorphic, hypogenous, 3-merous, pedicellate, with perianth differentiated into calyx and corolla; sepals 3, free, persistent, sometimes coriaceous, enclosing fruits; petals 3, free, delicate, ephemeral, yellow, sometimes with a dark spot at  base (Hydrocleys Rich.); stamens 3 to numerous, in one or more series, the more external frequently reduced to staminodes, filaments distinct, anthers rimose, linear, basifixed, with two locules; gynoecium apocarpous, with 3 to many carpels distributed along a receptacle, carpels free or coherent at base, 1-loculate, with many ovules and laminar placentation, stigma linear, style conspicuous or absent. Fruit a membranaceous follicle with adaxial dehiscence; seeds U-shaped, numerous; endosperm absent.

Notes on delimitation

  • Some authors, based on morphological and molecular analysis, include Limnocharitaceae within Alismataceae sensu lato, but this is not a consensus. According to Lethonen and Myllys (2008), only Limnocharis Humb. & Bonpl. is nested within Alismataceae. Furthermore, in most treatments the Limnocharitaceae and Alismataceae have been considered as distinct families because the Alismataceae sensu stricto form a monophyletic group.
  • Limnocharitaceae and related families (Alismataceae and Butomaceae) are considered as primitive monocotyledons.

Distribution in the Neotropics

  • Hydrocleys  is distributed among tropical and subtropical regions of Central and South America, and south of Mexico.
  • Limnocharis is endemic to the Neotropics, occurring mainly in South America.

Distinguishing characters (always present)

Limnocharitaceae is distinguishable on basis in the presence of:

  • Laticifers.
  • Flowers hermaphrodite with yellow petals, sometimes with dark spots on the base.
  • Fruits follicles.
  • Numerous seeds with ornamentation (pubescent or costate).
  • Large, strongly curved embryos.

Other important characters

Key differences from similar families

  • Limnocharitaceae can be distinguished from Alismataceae based on their yellow flowers, many ovules per carpel, laminar placentation and presence of follicles. Members of Alismataceae possess white or pink flowers, generally one ovule per carpel, basal placentation, and achenes.
  • Limnocharitaceae can be distinguished from Butomaceae on the basis of the presence of latex and large, strongly curved embryos. Members of Butomaceae possess straight embryos and lack laticifers.

Number of genera

  • Limnocharitaceae includes three genera and about seven species distributed among tropical regions of both hemispheres.
  • Two genera occur in the Neotropics: Limnocharis and Hydrocleys.

Useful tips for generic identification

  • Limnocharis - Leaves glaucous; carpels numerous, semicircular; styles absent; seeds with transversal ribs.
  • Hydrocleys -Leaves light green; carpels 3-8, linear-lanceolate; styles conspicuous; seeds glandular-pubescent.

Status

  • Both genera (Limnocharis and Hydrocleys) are native to the Neotropics.

General notes

  • Some native species include aquarium and ornamental pond plants.

Important literature

Haynes, R. R. & Holm-Nielsen, L. B. 1986. 192. Limnocharitaceae. In G. Harling, & L. Andersson (eds) Flora of Ecuador 26: 25-34.

Haynes, R. R. & Holm-Nielsen, L. B. 1992. The Limnocharitaceae. Fl. Neotrop. Monogr. 56: 1-34.

Lehtonen, S. & Myllys, L. 2008. Cladistic analysis of Echinodorus (Alismataceae): simultaneous analysis of molecular and morphological data. Cladistics 24: 218-239.

Novelo R., A. & Lot H., A. 1994. Limnocharitaceae. In G. Davidse, M. Sousa S. & A. O. Chater (eds) Flora Mesoamericana. México, D. F.: Universidad Nacional Autónoma de México. v. 6, p. 8-9.

Pansarin, E. R. & Amaral, M. C. E. 2002. Limnocharitaceae. In M. G. L. Wanderley, G. J. Shepherd & A. M. Giulietti (eds) Flora Fanerogâmica do Estado de São Paulo. São Paulo, Hucitec, v. 2. p.155-157.

Pedersen, T. M. & Klein R. M. 1976. Limnocaritáceas. In P. R. Reitz (ed.) Flora Ilustrada Catarinense, parte I, fasc. Limn. Itajaí, Herbário 'Barbosa Rodrigues', 9p., est. 1.

Seubert, M. 1842. Butomaceae. In C. F. P. Martius & A. G. Eichler (eds) Flora brasiliensis. Monachii, Typographia Regia, v. 3, pt. 1, p. 115-118, tabs. 13-16.

How to cite

Pansarin, E.R. (2009). Neotropical Limnocharitaceae. 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/Limnocharitaceae.htm.