Malvaceae

Malvaceae, or the mallow family, is a family of flowering plants containing over 200 genera with close to 2,300 species. Well known members of this family include okra, jute and cacao. The largest genera in terms of number of species include Hibiscus (300 species), Sterculia (250 species), Dombeya (225 species), Pavonia (200 species) and Sida (200 species).

Taxonomy

The circumscription of the Malvaceae is very controversial. The traditional Malvaceae sensu stricto comprises a very homogeneous and cladistically monophyletic group. Another major circumscription, Malvaceae sensu lato, has been more recently defined on the basis that newer techniques have shown that the commonly recognised families Bombacaceae, Tiliaceae, and Sterculiaceae, which have always been considered very close to Malvaceae s.s., are not monophyletic groups. Thus the Malvaceae have been expanded to include all of these families so to have a monophyletic group. Adopting this circumscription, Malvaceae incorporates a much larger number of genera.

This article is based on the second circumscription, as presented by the Angiosperm Phylogeny Website. The Malvaceae s.l. (hereafter simply "Malvaceae") comprise nine subfamilies. A tentative cladogram of the family is shown below. The diamond denotes a poorly supported branching (<80%).

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It is important to point out the relationships between these subfamilies are still either poorly supported or almost completely obscure, so that the very definition of the family may change dramatically as new studies are published.

If looking for information about the traditional Malvaceae s.s., we recommend referring to Malvoideae, the subfamily that approximately corresponds to that group.

Description

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Most species are herbs or shrubs but some are trees and lianas.

Leaves and stems

Leaves are generally alternate, often palmately lobed or compound and palmately veined. The margin may be entire, but when dentate a vein ends at the tip of each tooth (malvoid teeth). Stipules are present. The stems contain mucous canals and often also mucous cavities. Hairs are common, and are most typically stellate.

Flowers

The flowers are commonly borne in definite or indefinite axillary inflorescences, which are often reduced to a single flower, but may also be cauliflorous, oppositifolious or terminal. They often bear supernumerary bracts. They can be unisexual or bisexual and are generally actinomorphic, often associated with conspicuous bracts, forming an epicalyx. They generally have five valvate sepals, most frequently basally connate. Five imbricate petals. The stamens are five to numerous, connate at least at their bases, but often forming a tube around the pistils. The pistils are composed of two to many connate carpels. The ovary is superior, with axial placentation. Capitate or lobed stigma. The flowers have nectaries made of many tightly packed glandular hairs, usually positioned on the sepals.

Fruits

fruits.|thumb]] Most often a loculicidal capsule, a schizocarp or nut.

Importance

A number of species are pests in agriculture, including Abutilon theophrasti and Modiola caroliniana, and others that are garden escapes. Cotton (4 species of Gossypium), kenaf (Hibiscus cannabinus), cacao, kola nut and okra (Abelmoschus esculentus) are important agricultural crops. The fruit and leaves of baobabs are edible, as is the fruit of the durian.

References

Bayer, C. and K. Kubitzki 2003. Malvaceae, pp. 225-311. In K. Kubitzki (ed.), The Families and Genera of Vascular Plants, vol. 5, Malvales, Capparales and non-betalain Caryophyllales.

Judd, W. S., C. S. Campbell, E. A. Kellogg and P. F. Stevens. Plant Systematics: A Phylogenetic Approach.

Maas, P. J. M. and L. Y. Th. Westra. 2005. Neotropical Plant Families (3rd edition).

(abstract online here).

See also

Florissantia -- an extinct Cenozoic genus

External links

Malvaceae in Topwalks

Alverson, William S., Barbara A. Whitlock, Reto Nyffeler, Clemens Bayer and David A. Baum. 1999. Phylogeny of the core Malvales: evidence from ndhF sequence data. American Journal of Botany 86: 1474-1486.

Core Malvales from Tree of Life

Malvaceae: plants of Hawaii (image gallery) from HEAR

Malvaceae Gallery

Malvaceae of Mongolia in FloraGREIF

Category:Malvales families