The Teloschistaceae are a large family of mostly lichen-forming fungi belonging to the class Lecanoromycetes in the division Ascomycota. Many members of the Teloschistaceae are readily identifiable by their vibrant orange to yellow hue, a result of their frequent anthraquinone content. The presence of these anthraquinone pigments, which confer protection from ultraviolet light, enabled this group to expand from shaded forest habitats to harsher environmental conditions of sunny and arid ecosystems during the Late Cretaceous. Collectively, the family has a cosmopolitan distribution, although members occur predominantly in subtropical and temperate regions. Although most members are lichens that either live on rock or on bark, about 40 species are lichenicolous fungi–meaning they live on other lichens.
Teloschistaceae lichens typically have one of a few physical growth forms. Depending on the species, the thallus (the main body of the lichen) is either leaf-like (foliose), bushy or shrub-like (fruticose) or crust-like (crustose). These lichens typically partner with a photosynthetic companion (a ) from the green algal genus Trebouxia or similar genera. Teloschistaceae members are also characterised by their (the fruiting bodies where sexual reproduction occurs), which generally have well-defined , contributing to the lichen's overall structure and appearance. A distinct feature of Teloschistaceae is the bluish reaction of the ascus tip's external layer to iodine – the ascus being the spore-producing structure. The are released through a longitudinal slit in the tip of the ascus, a unique trait common to this group of lichens.
The family, first formally proposed in 1898, was extensively revised in 2013, including the recognition of three distinct subfamilies (Caloplacoideae, Teloschistoideae, and Xanthorioideae), and the creation or resurrection of 31 genera. Since 2013, several dozen new genera have been added to the family, but there has been some debate about these additions. Ongoing DNA studies are helping to provide clearer insights into how the different groups within this family are related. Depending on the source consulted, the family is estimated to contain up to more than 1000 species and 117 genera. Three species from the Teloschistaceae have been globally assessed for conservation status, with others appearing on regional lists, such as the rare New Zealand species Caloplaca allanii. The full diversity of this family remains underexplored in vast regions like South America and China.
Systematics
Historical taxonomy
The first members of the present-day Teloschistaceae to be formally described were the common sunburst lichen (Xanthoria parietina) and the gold-eye lichen (Teloschistes chrysophthalmus). These were two of several dozen lichen species described by Swedish taxonomist Carl Linnaeus, the former in his influential 1753 treatise Species Plantarum, and the latter in his 1771 work Mantissa Plantarum II.
In his 1852 work Synopsis Lichenum Blasteniosporum ("Synopsis of Lichen Blasteniospores"), Italian lichenologist Abramo Bartolommeo Massalongo attempted to classify what he called "blasteniospore lichens". This term referenced species, diverse in growth forms and appearance, united by the distinct spores now attributed to the family Teloschistaceae. These are spores that are divided into two compartments () separated by a central septum with a perforation. Although Massalongo's efforts to arrange these taxa into more natural genera were largely ignored by later contemporaries, several of his proposed genera were resurrected for use 16 decades later, such as Blastenia, Gyalolechia, Pyrenodesmia, and Xanthocarpia.