''Pyrenodesmia'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

lichen A lichen ( , ) is a hybrid colony (biology), colony of algae or cyanobacteria living symbiotically among hypha, filaments of multiple fungus species, along with yeasts and bacteria embedded in the cortex or "skin", in a mutualism (biology), m ...

-forming

fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...

in the family

Teloschistaceae The Teloschistaceae are a large family (biology), family of mostly lichen-forming fungi belonging to the class (taxonomy), class Lecanoromycetes in the division (botany), division Ascomycota. The family has a cosmopolitan distribution, althoug ...

. The genus currently includes 23 recognized species but is believed to contain many more unnamed taxa. The genus was

circumscribed In geometry, a circumscribed circle for a set of points is a circle passing through each of them. Such a circle is said to ''circumscribe'' the points or a polygon formed from them; such a polygon is said to be ''inscribed'' in the circle. * Circum ...

in 1852 by Italian lichenologist

Abramo Bartolommeo Massalongo Abramo Bartolommeo Massalongo (13 May 1824 – 25 May 1860) was an Italian paleobotanist and lichenologist. He was born in Tregnago in the Province of Verona and took a great interest in botany as a young man. Massalongo joined the faculty of med ...

. It is characterised by the complete absence of

anthraquinone Anthraquinone, also called anthracenedione or dioxoanthracene, is an aromatic hydrocarbon, aromatic organic compound with formula . Several isomers exist but these terms usually refer to 9,10-anthraquinone (IUPAC: 9,10-dioxoanthracene) wherein th ...

s and the presence of Sedifolia-gray

pigments A pigment is a powder used to add or alter color or change visual appearance. Pigments are completely or nearly solubility, insoluble and reactivity (chemistry), chemically unreactive in water or another medium; in contrast, dyes are colored sub ...

in both the

thallus Thallus (: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. A thallus usually names the entir ...

and

apothecia An ascocarp, or ascoma (: ascomata), is the fruiting body ( sporocarp) of an ascomycete phylum fungus. It consists of very tightly interwoven hyphae and millions of embedded asci, each of which typically contains four to eight ascospores. As ...

. These lichens are typically found in

calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime (mineral), lime or being chalky. The term is used in a wide variety of Science, scientific disciplines. In zoology ''Calcare ...

outcrops in the Northern Hemisphere, with

biodiversity Biodiversity is the variability of life, life on Earth. It can be measured on various levels. There is for example genetic variability, species diversity, ecosystem diversity and Phylogenetics, phylogenetic diversity. Diversity is not distribut ...

centres in the Mediterranean basin, Central Asia, and arid regions of western North America.

Taxonomy

The genus ''Pyrenodesmia'' was

(1852). In his original conception, Massalongo included four species (''P. agardhiana'', ''P. chalybaea'', ''P. olivacea'', and ''P. variabilis'') and three infraspecific taxa (''P. variabilis'' β. ''lilacina'', ''P. variabilis'' δ. ''pulchella'', and ''P. variabilis'' γ. ''fusca''). These

taxa In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and ...

all grow on calcareous outcrops, lack anthraquinones, and have Sedifolia‐gray both in their thallus and apothecia. Ulf Arup and colleagues (2013) resurrected the genus, recognizing both ''Pyrenodesmia'' ''

sensu stricto ''Sensu'' is a Latin word meaning "in the sense of". It is used in a number of fields including biology, geology, linguistics, semiotics, and law. Commonly it refers to how strictly or loosely an expression is used in describing any particular c ...

'' and the informal group ''Pyrenodesmia'' ''sensu lato''. ''Pyrenodesmia'' sensu stricto includes species that lack anthraquinones and possess Sedifolia-gray, while ''Pyrenodesmia'' sensu lato also includes species with anthraquinones in the apothecia. The

taxonomy image:Hierarchical clustering diagram.png, 280px, Generalized scheme of taxonomy Taxonomy is a practice and science concerned with classification or categorization. Typically, there are two parts to it: the development of an underlying scheme o ...

of the genus remains complex, with several taxa awaiting more robust data for proper classification.

Description

''Pyrenodesmia'' species have a

crustose Crustose is a Habit (biology), habit of some types of algae and lichens in which the organism grows tightly appressed to a substrate, forming a biological layer. ''Crustose'' adheres very closely to the Substrate (biology), substrates at all poin ...

, or thallus that is white, gray, or brown in colour. The is usually represented by an alveolate cortex and is . The apothecia are or rarely in form, with brown, gray, or black and . are with a short to large long

septum In biology, a septum (Latin language, Latin for ''something that encloses''; septa) is a wall, dividing a Body cavity, cavity or structure into smaller ones. A cavity or structure divided in this way may be referred to as septate. Examples Hum ...

. are present or absent, gray or black, and are to somewhat spherical. In ''Pyrenodesmia'', the thalli, apothecia, and pycnidia always lack anthraquinones but have Sedifolia-gray pigments.

Habitat and distribution

''Pyrenodesmia'' species are mainly distributed in the Mediterranean region, Central Asia, and desert regions of western North America, with a few taxa found in other parts of Europe, Asia, and North America. They exclusively grow on rocks, inhabiting

outcrops in Europe and base-rich

siliceous Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant ...

outcrops in Central Asia and the United States. These lichens can be found in sunlit conditions from coast to

alpine zone Alpine tundra is a type of natural region or biome that does not contain trees because it is at high elevation, with an associated alpine climate, harsh climate. As the latitude of a location approaches the poles, the threshold elevation for alp ...

s, with some species such as ''P. helygeoides'' growing on acidic siliceous boulders in water.

Species

References

{{Taxonbar, from=Q27440395 Teloschistales Lichen genera Teloschistales genera Taxa described in 1853 Taxa named by Abramo Bartolommeo Massalongo