Neotropical Cabombaceae

Lidyanne Yuriko Saleme Aona

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

Description

Perennial aquatic glabrous plants, rarely annual; rhizome elongated, fixed to the substrate, stems elongated and submersed to distally floating. Leaves simple, petiolate, heterophyllous, floating, peltate, narrowly elliptic to broadly ovate, the submerse ones (only in Cabomba Aubl.) dissected, palmate; stipules absent. Flowers on long pedicels, opening above the water, solitary, hermaphrodite, symmetry radial, hypogynous, tepals 6, white, pink, purple or yellow, the inner tepals (petals) with nectariferous auricles near the base; stamens 3-36, free, filaments flattened, anthers oblong, basifixed, with two thecae, extrorse with longitudinal dehiscence, carpels (1- )2-4(-18), free, ovules (1-)2-5, placentation laminar. Fruit achene-like, coriaceous, indehiscent; seeds 1-5 per fruit, embryo small, endosperm reduced, perisperm abundant.

Notes on delimitation

  • Cabombaceae is in the order Nympheales together with Nymphaeaceae and Hydatellaceae.
  • Saarela et al. (2007) suggest a few additional possible synapomorphies for Nymphaeales, such as hydrolysable tannins which in this group (e.g. in Nuphar Sm.) are different from those found elsewhere (Gottlieb et al. 1993; Ishimatsu et al. 1989) - although of course Hydatellaceae are a poorly known group.

Distribution in the Neotropics

Two genera:

  • Cabomba (c. 5 species, widely distributed from the USA to Argentina), leaves heterophyllous, inner tepals bearing nectaries.
  • Brasenia schreberi J.F.Gmel., a wind pollinated species with reduced flowers, distributed worldwide and cultivated for its edible shoots.

Distinguishing characters (always present)

  • Cabombaceae are rather small-flowered 'waterlilies', with few ovules or seeds in each carpel; they have floating stems and all their flower parts are free (Stevens 2008).

Other important characters

  • Petals (inner tepals) with auricular nectaries.
  • Placentation laminar.

Key differences from similar families

Cabombaceae is closely related to the true 'waterlilies', Nymphaeaceae, sharing with it several characters e.g:

However, in Cabombaceae the flowers are trimerous, with 6 tepals (vs. sepals 4-6(-12) and petals 6-70 in Nympheaceae), and leaves may be heterophyllous.

Number of genera

See above.

Useful tips for generic identification

  • Brasenia Schreb. is wind pollinated.
  • Cabomba has paired nectaries on its inner tepals and is pollinated by insects (Stevens 2008).

Notable genera and distinguishing features

See above

Status

  • Both genera are widely distributed and native. Species of the genus Cabomba are often used as aquarium plants.

Important literature

FERES, F. & AMARAL, M.C.E. 2003. Cabombaceae. In Wanderley, M. G. L., Shepherd, G. J. & Giulietti, A. M. (Eds.). Flora Fanerogâmica do Estado de São Paulo. Vol. 3. São Carlos, Editora RiMA. pp: 09-11.

GOTTLIEB, O., R., Kaplan, M. A. C., & Kubitzki, K. 1993. A suggested role of galloyl esters in the evolution of dicotyledons. Taxon 42: 539-552.

ISHIMATSU, M., Tanaka, T., Nonaka, G., Nishioka, I., Nishizawa, M., & Yamagishi, T. 1989. Tannins and related compounds. LXXIX. Isolation and characterisation of novel dimeric and trimeric hydrolyzable tannins, nuphrins C, D, E and F, from Nuphar japonicum DC. Chem. Pharmac. Bull. 37: 1735-1743.

ORGAARD, M. 1991. The genus Cabomba (Cabombaceae) - a taxonomic study. Nordic J. Bot. 11(2): 179-203.

SAARELA, J. M., Rai, H. S., Doyle, J. A., Endress, P. K., Mathews, S., Marchant, A. D., Briggs, B., & Graham, S. W. 2007. Hydatellaceae identified as a new branch near the base of the angiosperm phylogenetic tree. Nature 446: 312-315.

STEVENS, P. F. 2008. Angiosperm Phylogeny Website. Version 9, June 2008 [and more or less continuously updated since]. http://www.mobot.org/MOBOT/research/APweb/.

How to cite

Aona, L.Y.S. (2009). Neotropical Cabombaceae. 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/Cabombaceae.htm.