Caliciaceae
The Caliciaceae are a family of mostly lichen-forming fungi belonging to the class Lecanoromycetes in the division Ascomycota. Although the family has had its classification changed several times throughout its taxonomic history, the use of modern molecular phylogenetic methods has helped to establish its current placement in the order Caliciales. Caliciaceae contains 39 genera and about 670 species. The largest genus is Buellia, with around 300 species; there are more than a dozen genera that contain only a single species.
Most Caliciaceae grow on bark, dead wood, or rocks. Some members of this family, particularly those of the type genus, Calicium, are characterized by the presence of thin-walled and short-lasting asci and a mazaedium, which is an accumulation of loose, maturing spores covering the surface of the fruiting body. The resulting passive spore dispersal is relatively rare amongst the Ascomycota. The mazaedium, usually black, either sits atop a long thin stalk, or rests on the surface of the lichen substrate. Many other Caliciaceae species generate spores in an apothecium, which typically resembles a flattened black disc.
The family contains species with crustose, foliose, and, in a few instances, fruticose growth forms. The photobiont partner of Caliciaceae lichens is usually from the green algal genus Trebouxia. Collectively, the family has a cosmopolitan distribution, and can be found on all major land masses. Although the family is best represented in mountainous areas of temperate and tropical regions, a few hardy species can survive the harsh environment offered by Antarctica's McMurdo Dry Valleys by growing in cracks on the surface of rocks. Five Caliciaceae species are included in the International Union for Conservation of Nature's Red List of Threatened Species. Some air pollution-resistant species in the genus Pyxine have been investigated for use as biomonitors of heavy metal pollution. Several fossils of Caliciaceae found as inclusions in amber have been used to evaluate the evolutionary history of the family.
Systematics
Caliciaceae was circumscribed in 1826 by the French botanist François Fulgis Chevallier. He wrote about the family: "The Calicinees are a small group of plants, the growth of which has misled botanists. They are small parasitic fungi on the crusts of lichens, mainly on Variola and common porin, and on dead canes." The type genus of the Caliciaceae is Calicium, originally circumscribed in 1794 by Christiaan Hendrik Persoon; this genus is itself typified by Calicium viride. Buelliaceae and Pyxinaceae are historical families created to contain taxa that are now included in the Caliciaceae.Two other calicioid families with "Caliciaceae" in their name – Microcaliciaceae and Mycocaliciaceae – contain species formerly considered to be closely related to the Caliciaceae. The monogeneric Microcaliciaceae has non-lichenized, calicioid species that are parasites on lichens or free-living colonies of algae, while Mycocaliciaceae contains non-lichenized calicioid fungi lacking a mazaedium and utilising active spore dispersal.
File:Calicium_hyperellum.jpg|thumb|right|The lichen Calicium viride as it appeared in Smith and Sowerby's English Botany, Vol. 10.
Classification
The Caliciaceae and other morphologically similar pin lichens with mazaedium-forming ascomata featuring passive spore dispersal used to be grouped together in the order Caliciales, which was for a long time considered to be a model example of a monophyletic grouping of taxa. Historically, the family has also been placed by various authors in the orders Coryneliales, Helotiales, and the now-obsolete Sphaeriales, depending on which phenotypic characteristics were considered to be the most important.The Swedish lichenologist Leif Tibell spent much of his career studying calicioid lichens, and used a variety of techniques to help him understand relationships of taxa in this group, including phenetic and cladistic analyses of morphology, and investigation of secondary chemistry. He suggested in 1984 that the order was polyphyletic and that the main identifying features of the Caliciales had evolved independently in several different unrelated groups. He restricted the order to three families that he considered to be the "core" of the group. Preliminary phylogenetic analysis showed that Mycocaliciaceae and Sphinctrinaceae belonged to the class Eurotiomycetes, while Caliciaceae appeared to group with the order Lecanorales. The proposition that mazaediate fungi are dispersed throughout the Ascomycota was confirmed later in several molecular phylogenetic studies. The six genera that were included by Tibell in the Caliciaceae in his 1984 proposed classification of calicioid fungi are still in the family today.
Phylogenetics
The Caliciaceae and the Physciaceae were shown to be closely related in molecular studies. Both of these families were tentatively placed in the Teloschistales as part of the suborder Physciineae. Since the mazaedia-producing species of the Caliciaceae were nested within the genera Dirinaria, Pyxine, and Physcia, some authors treated all the members of the Caliciaceae and Physciaceae as one family, and the name Physciaceae was proposed for conservation in 2002. With the appearance of additional phylogenetic studies since then, however, a two-family concept of Caliciaceae and Physciaceae has been preferred by most authorities. In 2012, the suborder Physciineae was promoted to ordinal status and the name Caliciales was resurrected. In its modern circumscription, the order Caliciales contains these two families. A large molecular study of the Caliciaceae-Physciaceae clade published in 2016 has helped to sort out natural relationships in this group, and more clearly define generic delimitations.The genus Culbersonia, previously classified in the Physiaceae because of its morphological resemblance to Physconia, was shown to be a member of the Caliciaceae in 2019. In phylogenetic analysis, it groups together in a clade with Pyxine and Dirinaria. These three genera are distinguished from other Caliciaceae in the appressed foliose growth form, the absence of a mazaedium, and ecologically by their predominance in the subtropics and tropics.
Description
The thallus, when present, is crustose, with a texture that is verrucose, granular, or areolate. Its colour is typically grey, yellow, or greenish. Sometimes it is immersed within the outer layers of the bark of its host. The ascomata are more or less spherical or hemispherical, situated atop a long stalk in some species, but sessile in other species. When it is present, the stalk is usually melanized. The form of the ascomata is either apotheciate or mazaediate. The apothecium consists of the asci and associated hymenium, and the sterile, structural, and supportive part of the apothecium, called the excipulum. In apotheciate Caliciaceae species, the apothecium is typically lecidiene, rather than lecanorine. The tissue structure of the excipulum is either prosoplectenchymatous or paraplectenchymatous, and is hyaline to dark brown. The genus Acroscyphus, which contains the single widespread but rare species A. sphaerophoroides, is a peculiar exception to the typical morphology of the Caliciaceae: it has a finger-like thallus, immersed ascocarps on podetia, and a yellow to orange medulla.The asci of Caliciaceae species are cylindrical to broadly club-shaped. They are attached to croziers, which are hook-shaped structures on cells that form at the base of the asci. The asci have thin walls and lack any internal structures at the tip. As a result, they last for only a short time before they degrade, and the ascospores within are released passively in a mazaedial mass. The hamathecium consists of unbranched to slightly branched paraphyses that are amyloid. There are usually eight spores per ascus, although sometimes this is reduced to four, or increased to 16–32 per ascus. The ascospores are dark brown, with a surface that is either smooth or ornamented with remnants from the rupture of the outer wall layers. They have either zero or one septa. The spores of Texosporium lichens have a unique ornamentation that is created by paraphyses that stick to the surface; this feature may help provide protection against desiccation or DNA-damaging radiation encountered when exposed in sunny habitats. The conidiomata produced by Caliciaceae species are in the form of pycnidia. The conidia lack a septum, are rod-shaped to thread-shaped in form, and are hyaline.
The secondary chemistry of Caliciaceae species is variable. Chemicals that are commonly reported from the family are depsides, terpenes, depsidones, and lichexanthone. Sometimes anthraquinones are present when the thallus is pigmented. Acroscyphus is again an exception, as it contains secondary compounds not found in other Caliciaceae, including chloroatranorin, rugulosin, zeorin, and chrysophanic acid.
Genera
, Species Fungorum accepts 39 genera and 669 species in the family Caliciaceae. This is a list of the genera in the Caliciaceae, based on a 2020 review and summary of fungal classification by Wijayawardene and colleagues. Following the genus name is the taxonomic authority, year of publication, and the number of species:- Acolium – 5 spp.
- Acroscyphus – 1 sp.
- Allocalicium – 1 sp.
- Amandinea – 35 spp.
- Australiaena – 1 sp.
- Baculifera – 14 spp.
- Buellia – 300 spp.
- Burrowsia – 1 sp.
- Calicium – ca. 30 spp.
- Chrismofulvea – 4 spp.
- Ciposia – 1 sp.
- Cratiria – ca. 20 spp.
- Culbersonia – 1 sp.
- Dermatiscum – 3 spp.
- Dermiscellum – 1 sp.
- Dimelaena – 10 spp.
- Diploicia – ca. 12 spp.
- Diplotomma – ca. 30 spp.
- Dirinaria – ca. 35 spp.
- Endohyalina – 10 spp.
- Fluctua – 1 sp.
- Gassicurtia – 30 spp.
- Hypoflavia – 3 spp.
- Monerolechia – 4 spp.
- Orcularia – 4 spp.
- Pseudothelomma – 2 spp.
- Pyxine – ca. 75 spp.
- Redonia – 2 spp.
- Santessonia – 10 spp.
- Sculptolumina – 4 spp.
- Sphinctrinopsis – 1 sp.
- Stigmatochroma – 9 spp.
- Tetramelas – 16 spp.
- Texosporium – 1 sp.
- Thelomma – 5 spp.
- Tholurna – 1 sp.
- Tylophoropsis – 1 sp.