Umbilicaria is a genus of lichen-forming fungi in the family Umbilicariaceae, established by Georg Franz Hoffmann in 1789. Its members are foliose, leaf-like lichens that grow on rock and are attached to the surface at a single central point — the — giving them their characteristic navel-like form. Species occur on every continent and are especially associated with exposed siliceous rock in cold climates, including alpine, arctic, boreal, and Antarctic environments. The genus is commonly known as rock tripe, a name that reflects a long history of use as an emergency food source in northern regions.
The in Umbilicaria is a green alga of the genus Trebouxia. Reproduction is varied: many species reproduce sexually by ascospores, while others produce asexual from the lower thallus surface or lichenized propagules such as isidia or soredia. The secondary chemistry of the genus is dominated by gyrophoric acid, a tridepside detected in the great majority of species surveyed. Umbilicaria species are slow-growing pioneers of bare rock surfaces, and several have been studied as models for lichen cold tolerance and desiccation survival. The number of accepted species is debated, because authors differ over the circumscription of the genus within Umbilicariaceae.
Taxonomy
Umbilicaria was established by Georg Franz Hoffmann in 1789 in the first fascicle of his Descriptio et adumbratio plantarum e classe cryptogamica Linnaei, quae lichenes dicuntur;
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