Malvaceae

Malvaceae
Least mallow, Malva parviflora
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Rosids
Order:	Malvales
Family:	Malvaceae Juss.
Subfamilies
Bombacoideae Brownlowioideae Byttnerioideae Dombeyoideae Grewioideae Helicteroideae Malvoideae Sterculioideae Tilioideae

The Malvaceae, or the mallows, are a family of flowering plants estimated to contain 243 genera with 4225+ species. Well-known members of this family include okra, cotton, and cacao. The largest genera in terms of number of species include Hibiscus (300 species), Sterculia (250 species), Dombeya (250 species), Pavonia (200 species) and Sida (200 species).

Taxonomy and nomenclature

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

Subfamilies

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%).

Byttnerioideae: 26 genera, 650 species, pantropical, especially South America Grewioideae: 25 genera, 770 species, pantropical ♦ Sterculioideae: 12 genera, 430 species, pantropical Tilioideae: three genera, 50 species, northern temperate regions and Central America Dombeyoideae: about 20 genera, about 380 species, palaeotropical, especially Madagascar and Mascarenes Brownlowioideae: eight genera, about 70 species, especially palaeotropical Helicteroideae: eight to 12 genera, 10 to 90 species, tropical, especially Southeast Asia ♦ Malvoideae: 78 genera, 1,670 species, temperate to tropical Bombacoideae: 12 genera, 120 species, tropical, especially Africa and America

It is important to point out the relationships between these subfamilies are still either poorly supported or almost completely obscure, so the circumscription 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.

Names

The English common name 'mallow' (also applied to other members of Malvaceae) comes from Latin malva (also the source for the English word "mauve"). Malva itself was ultimately derived from the word for the plant in ancient Mediterranean languages. Cognates of the word include Ancient Greek μαλάχη (malákhē) or μολόχη (molókhē), Modern Greek μολόχα (molóha), modern Arabic: ملوخية‎‎ (mulukhiyah) and modern Hebrew: מלוחיה‎ (molokhia).

Description

Pavonia odorata

Alcea rosea is a common garden flower in Malvaceae

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

Leaves and stems

Stellate hairs on the underside of a dried leaf of Malva alcea

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, with five imbricate petals. The stamens are five to numerous, and 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, with capitate or lobed stigma. The flowers have nectaries made of many tightly packed glandular hairs, usually positioned on the sepals.

Fruits

Durian fruits

The fruits are most often loculicidal capsules, schizocarps or nuts.

Pollination

Self-pollination is often avoided by means of protandry. Most species are entomophilous (pollinated by insects).

Importance

A number of species are pests in agriculture, including Abutilon theophrasti and Modiola caroliniana, and others that are garden escapes. Cotton (four species of Gossypium), kenaf (Hibiscus cannabinus), cacao (Theobroma cacao), kola nut (Cola spp.), and okra (Abelmoschus esculentus) are important agricultural crops. The fruit and leaves of baobabs are edible, as is the fruit of the durian. A number of species, including Hibiscus syriacus, Hibiscus rosa-sinensis and Alcea rosea are garden plants.

See also

• Florissantia, an extinct Cenozoic genus

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

• 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.

External links

• Malvaceae.info: Malvaceae Gallery
• Topwalks.net: Malvaceae
• Tree of Life.org: Core Malvales
• HEAR.org — Malvaceae: plants of Hawaii — image gallery.
• GREIF Flora: Malvaceae of Mongolia