Teloschistaceae
The Teloschistaceae are a large family of mostly lichen-forming fungi belonging to the class Lecanoromycetes in the division Ascomycota. The family has a cosmopolitan distribution, although its members occur predominantly in temperate regions. Most members are lichens that either live on rock or on bark, but about 40 species are lichenicolousmeaning they are non-lichenised fungi that live on other lichens. 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.
Teloschistaceae lichens typically have one of a few physical growth forms. Depending on the species, the thallus is either leaf-like, bushy or shrub-like, or crust-like. These lichens typically partner with a photosynthetic companion from the green algal genus Trebouxia. Teloschistaceae members are also characterised by their , which generally have a well-defined. In the Teloschistaceae, the tip of the ascus, the structure that produces spores, characteristically turns blue when stained with iodine. The ascospores are released through a longitudinal slit in the ascus tip, a unique trait common to this family of lichens.
The family, first formally proposed in 1898, was extensively revised in 2013, including the creation or resurrection of 31 genera. Three subfamilies – Caloplacoideae, Teloschistoideae, and Xanthorioideae – are recognised. 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. The family contains more than 1,000 species in around 125 genera. Three species from the Teloschistaceae have been globally assessed for conservation status and others, such as the rare New Zealand species Caloplaca allanii, appear on regional lists. The full diversity of this family remains underexplored in vast regions like South America and China. Regarding human interactions and applications, although lacking any major economic impact, several rock-dwelling Teloschistaceae species are known to damage marble surfaces, and others are used in some traditional medicines. One member, Rusavskia elegans, is used in research as a model organism to investigate resilience against the harsh conditions of outer space.
Systematics
Historical taxonomy
The first members of the present-day Teloschistaceae to be formally described were the common sunburst lichen and the gold-eye lichen. These were two of several dozen lichen species described by the Swedish taxonomist Carl Linnaeus, the former in his influential 1753 treatise Species Plantarum, and the latter in his 1771 work Mantissa Plantarum Altera.In his 1852 work Synopsis Lichenum Blasteniosporum, the 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 small hole. Although Massalongo's efforts to arrange these taxa into more natural genera were largely ignored by subsequent researchers, several of his proposed genera were resurrected for use 16 decades later, such as Blastenia, Gyalolechia, Pyrenodesmia, and Xanthocarpia.
File:Caloplaca variabilis Müll. Arg 918275.jpg|thumb|alt=Microscopic view of an oval-shaped lichen ascocarp with a cluster of circular, brownish-orange spores, each displaying intricate, radiating patterns.|upright=0.7|right|An ascus of the crustose lichen Pyrenodesmia variabilis, containing eight polarilocular
The family Teloschistaceae was formally circumscribed by the lichenologist Alexander Zahlbruckner in 1898. In his initial version, he grouped together foliose and fruticose taxa having polarilocular or four-locule, including the genera Xanthoria, Teloschistes, and Lethariopsis. At that time, the growth form of the lichen was often used in classical lichen taxonomy to segregate groups of species into families, and so in a subsequent publication, Zahlbruckner introduced the family Caloplacaceae to contain crustose lichens with polarilocular ascospores; this family included the genera Caloplaca, Blastenia, Bombyliospora, and Protoblastenia. The distinctness of the family Caloplacaceae was largely rejected by other authors, and it is now a historical synonym of Teloschistaceae. In another older classification, crustose genera were grouped together in the family Blasteniaceae or the Placodiaceae. In 1971, Carroll William Dodge proposed the family Xanthoriaceae to contain Xanthodactylon, Xanthopeltis, and Xanthoria, but it was not validly published.
In the 20th century, particularly with the widespread use of electron microscopy, the details of ascus structure became important considerations in the taxonomy of lichen-forming fungi. Studies on several Teloschistaceae species have noted the consistent presence of a cap-like zone at the tip of the ascus that shows a strong reaction to iodine, characteristic of amyloid substances. Using advanced transmission electron microscopy, Rosmarie Honegger confirmed a unique type of ascus in Teloschistaceae, later named the Teloschistes-type. This ascus is distinguished by a special outer layer that reacts to certain stains and lacks the typical structures seen at the tip, opening in an unusual pattern during spore release. The presence of this ascus type was later used as a diagnostic for the family Teloschistaceae following an ultrastructural study that corroborated Honegger's work. In 1989 Ingvar Kärnefelt revised the family, accepting ten genera, and this served as the main taxonomic classification for the family until the molecular era. In one of the last classifications of the family before the widespread use and implementation of molecular techniques, the Outline of the Ascomycota accepted 12 genera in Teloschistaceae in 2006: Caloplaca, Cephalophysis, Fulgensia, Huea, Ioplaca, Josefpoeltia, Seirophora, Teloschistes, Xanthodactylon, Xanthomendoza, Xanthopeltis, and Xanthoria. The family continues to undergo significant changes. For example, in 2020, of all fungal families, Teloschistaceae had the fourth-highest number of new fungal names, including 8 genera, 48 new species and infraspecific taxa, and 72 new combinations.
Etymology
As is standard practice in botanical nomenclature, the name Teloschistaceae is based on the name of the type genus, Teloschistes, with the ending indicating the rank of family. The genus name, assigned by the Norwegian botanist Johannes M. Norman in 1852, comprises two Ancient Greek words: τέλος, meaning,, or ; and σχιστός, meaning,, or. It refers to the split ends of the thallus branches that are characteristic of that genus.Subfamilial and ordinal classification
Teloschistaceae is divided into three recognised subfamilies: Xanthorioideae, Caloplacoideae, and Teloschistoideae. In 2015, researchers proposed a fourth subfamily, Brownlielloideae, which was later shown by genetic studies to be a grouping based on mixed or misinterpreted data rather than a distinct lineage. Further analysis placed what was thought to be Brownlielloideae within the already established Teloschistoideae, suggesting the proposed subfamily was not a separate branch of the family tree. DNA evidence also dispersed members of the informally introduced subfamily Ikaerioideae across the three acknowledged subfamilies, primarily within Teloschistoideae. Despite this, Sergey Kondratyuk and colleagues continue to use Brownlielloideae and Ikaerioideae in their publications, assigning nine genera to the former and two to the latter. The well-supported subfamilies encompass a range of growth formscrustose, foliose, and fruticosedemonstrating the diverse evolutionary paths within the family. These groups are genetically distinct, each subfamily showing unique patterns in their nuclear large ribosomal subunit RNA sequences.- Caloplacoideae
- *Type genus: Caloplaca. Proposed by Ester Gaya and colleagues in 2012 and validly published in 2020, Caloplacoideae consists mostly of crustose lichens with a wide geographical spread and produces a range of unique chemical compounds.
- Teloschistoideae
- *Type genus: Teloschistes. Initially proposed in 2013 and validly published with a full diagnosis in 2020, this subfamily is predominantly found in the Southern Hemisphere.
- Xanthorioideae
- *Type genus: Xanthoria. Named by Gaya and colleagues in 2012 and formally validated in 2020, Xanthorioideae species are primarily distributed in the Northern Hemisphere.