''Tomnashia'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

lichen A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...

in the family

Teloschistaceae The Teloschistaceae are a large family of mostly lichen-forming fungi belonging to the class Lecanoromycetes in the division Ascomycota. The family, estimated to contain over 1800 species, was extensively revised in 2013, including the creation o ...

. It has four species of

saxicolous A saxicolous lichen is a lichen that grows on rock. The prefix "sax" from the Latin means "rock" or "stone". Characteristics Saxicolous lichens exhibit very slow growth rates. They may develop on rock substrates for long periods of time, give ...

(rock-dwelling),

crustose lichen Crustose lichens are lichens that form a crust which strongly adheres to the Substrate (biology), substrate (soil, rock, tree bark, etc.), making separation from the substrate impossible without destruction. The basic structure of crustose lichen ...

s that occur in southwestern North America.

Taxonomy

''Tomnashia'' was

circumscribed In geometry, the circumscribed circle or circumcircle of a polygon is a circle that passes through all the vertices of the polygon. The center of this circle is called the circumcenter and its radius is called the circumradius. Not every polyg ...

in 2017 by lichenologists

Sergey Kondratyuk Sergey Yakovlevich Kondratyuk ( uk, Сергій Якович Кондратюк) (born 17 May 1959) is a Ukrainian botanist specialising in lichenology. His research deals with the taxonomy, floristics, ecology and geography of lichens and lic ...

and Jae-Seoun Hur, who bestowed upon the

taxon In biology, a taxon (back-formation from ''taxonomy''; plural 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 nam ...

eponym An eponym is a person, a place, or a thing after whom or which someone or something is, or is believed to be, named. The adjectives which are derived from the word eponym include ''eponymous'' and ''eponymic''. Usage of the word The term ''epon ...

in honour of

Thomas Hawkes Nash III Thomas Hawkes Nash III (born November 13, 1945) is an American lichenologist. His research is about the biology and ecology of lichens, and the effects of air pollution on plants and lichens. He is known as an authority on the family Parmelia ...

, a significant contributor to lichenology, especially concerning North American lichen flora. The

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

of this genus is '' Tomnashia rosei'', which was originally described as ''Caloplaca rosei'' by

Hermann Edward Hasse Hermann Edward Hasse (12 January 1836 – 29 October 1915) was an American lichenologist.H. E. Hasse, Lichenist, Kerry Knudsen, Opuscula Philolichenum, 8: 59-66. 2010/ref> He wrote two important texts and numerous articles in his field. '' Hasse ...

in 1911. Through combined

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

analysis, it was determined that ''Tomnashia'' resides in the outermost position among

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...

groups of the ''Polycauliona'' subclade of the subfamily Xanthorioideae. This genus differs notably from other members of ''Polycauliona'' with its distinct characteristics and

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines * Morphology (archaeology), study of the shapes or forms of artifacts * Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies ...

Description

Presenting a varied range of colours, the crustose

thallus Thallus (plural: 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. Many of these organisms wer ...

of ''Tomnashia'' ranges from white, grey, and greenish-yellow to yellowish orange, or apricot orange, with some species having a unique waxy translucent appearance. The small, are usually orange to reddish-brown. Another unique attribute of this genus is its , which are and

hyaline A hyaline substance is one with a glassy appearance. The word is derived from el, ὑάλινος, translit=hyálinos, lit=transparent, and el, ὕαλος, translit=hýalos, lit=crystal, glass, label=none. Histopathology Hyaline cartilage is ...

. Its distinctive chemical composition includes substances such as

parietin Parietin is the predominant cortical pigment of lichens in the genus '' Caloplaca'', a secondary product of the lichen ''Xanthoria parietina'', and a pigment found in the roots of Curled Dock (''Rumex crispus''). It has an orangy-yellow color and ...

, fallacinal,

emodin Emodin (6-methyl-1,3,8-trihydroxyanthraquinone) is a chemical compound, of the anthraquinone family, that can be isolated from rhubarb, buckthorn, and Japanese knotweed (''Reynoutria japonica'' syn. ''Polygonum cuspidatum''). Emodin is particular ...

, teloschistin, and parietinic acid.

Habitat and distribution

Predominantly distributed in the southwestern part of North America, ''Tomnashia'' is found mainly on

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

rock and soil, but it can also grow on non-calcareous rocks. Some related genera, such as ''Polycauliona'' and '' Igneoplaca'', share a similar, relatively limited distribution in coastal southwestern North America. Other genera in the same subfamily, such as '' Massjukiella'' and '' Verrucoplaca'', have a much broader distribution in the Northern Hemisphere or worldwide.

Species

* ''

Tomnashia ludificans ''Tomnashia'' is a genus of lichen-forming fungi in the family Teloschistaceae. It has four species of saxicolous (rock-dwelling), crustose lichens that occur in southwestern North America. Taxonomy ''Tomnashia'' was circumscribed in 2017 by ...

'' * '' Tomnashia luteominia'' * '' Tomnashia nashii'' * '' Tomnashia rosei''

References

{{Taxonbar, from=Q63253315 Teloschistales Teloschistales genera Taxa described in 2017 Lichen genera Taxa named by Sergey Kondratyuk Taxa named by Jae-Seoun Hur