Urticaceae


The Urticaceae are a family, the nettle family, of flowering plants. The family name comes from the genus Urtica. The Urticaceae include a number of well-known and useful plants, including nettles in the genus Urtica, ramie, māmaki, and ajlai.
The family includes about 2,625 species, grouped into 53 genera according to the database of the Royal Botanic Gardens, Kew and Christenhusz and Byng. The largest genera are Pilea, Elatostema, Urtica, and Cecropia. Cecropia contains many myrmecophytes.
Urticaceae species can be found worldwide, apart from the polar regions.

Description

Urticaceae species can be shrubs, lianas, herbs, or, rarely, trees. Their leaves are usually entire and bear stipules. Urticating hairs are often present. They have usually unisexual flowers and can be both monoecious or dioecious. They are wind-pollinated. Most disperse their pollen when the stamens are mature and their filaments straighten explosively, a peculiar and conspicuously specialised mechanism.

Taxonomy

The APG II system puts the Urticaceae in the order Rosales, while older systems consider them part of the Urticales, along with Ulmaceae, Moraceae, and Cannabaceae. APG still considers "old" Urticales a monophyletic group, but does not recognise it as an order on its own.

Fossil record

The fossil record of Urticaceae is scattered and mostly based on dispersed fruits. Twelve species based on fossil achenes are known from the Late Cretaceous of Central Europe. Most were assigned to the extant genera Boehmeria, Debregeasia and Pouzolzia, while three species were assigned to the extinct genus Urticoidea. A Colombian fossil flora of the Maastrichtian stage has yielded leaves that resemble leaves of the tribe Ceropieae.

Phylogeny

Modern molecular phylogenetics suggest the following relationships :

Tribes and genera

The Urticaceae are subject to many bacterial, viral, fungal, and nematode parasitic diseases. Among them are: