Saturday, 19 October 2019
The Four Tribes of Malvoideae
Subfamily Malvoideae now comprises the traditional Malvaceae and has consistently emerged as a very homogeneous, monophyletic group. In a recent treatment of Malvoideae, Bayer and Kutbitzki (2003) divide the subfamily into four tribes: Gossypieae, Hibisceae, Kydieae, and Malveae.
The Malvoideae can be further ranked into the tribes listed below:
Tribe Gossypieae has been redifined to include eight genera: Gossypium, Cephalohibiscus, Cienfuegosia, Hampea, Kokia, Gossypioides, Lebronnecia and Thespesia. It is specifically separated from the Hibisceae tribe based on embryo structure and the presence of pigment glands. These glands are associated with the capacity to synthesize the pigment gossypol. The Gossypieae appear to be unique in possessing these glands and this capacity.
More than 50 species of Gossypium are distributed in arid to semi-arid regions of the tropics and subtropics. Of these, four species were independently domesticated for their fiber (cotton) in Africa, Asia and the Americas. Gossypium species exhibit extraordinary morphological variation, with a diverse array of characteristics, ranging from trailing herbaceous perennials to 15m tall trees.
Tribe Hibisceae is best known for its largest genus, Hibiscus — one of the world's most popular horticultural plant genera — which includes more than 300 species worldwide. The tribe Hibisceae includes (but is not limited to) : Abelmoschus, Hibiscadelphus, Hibiscus, Kosteletzkya, Malvaviscus, Pavonia, Radyera, Talipariti and Wercklea.
Tribe Malveae includes approximately 70 genera (1000 species) that encompass the majority of the morphological and taxonomic diversity in the Malvoideae subfamily. The genera of Malveae exhibit a broad geographic distribution, with representatives in both tropic and temperate areas in a variety of habitats. Around 15 of the 70 Malveae genera have mostly temperate distributions, while some of the largest genera in the tribe (Abutilon, Sida, Nototriche) have primarily tropical distributions.