''Phacopsis'' is a genus of lichenicolous (

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. They are parasites of members of the large lichen family Parmeliaceae, of which they are also a member. Originally proposed by

Edmond Tulasne Louis René Étienne Tulasne, a.k.a. Edmond Tulasne (12 September 1815 – 22 December 1885) was a French botanist and mycologist born in Azay-le-Rideau. He originally studied law at Poitiers, but his interest later turned to botany. As a yo ...

in 1852 to contain 3 species, ''Phacopsis'' now contains 10 species, although historically, 33 taxa have been described in the genus. Many of the species are poorly known, some of them having been documented only from the type specimen. ''Phacopsis'' species appear as partially immersed, shiny brown to black apothecia that cause

gall Galls (from the Latin , 'oak-apple') or ''cecidia'' (from the Greek , anything gushing out) are a kind of swelling growth on the external tissues of plants, fungi, or animals. Plant galls are abnormal outgrowths of plant tissues, similar to be ...

-like deformations on the thallus of the

host A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places * Host, Pennsylvania, a village in Berks County People *Jim Host (born 1937), American businessman * Michel Host ...

lichen. Features of ''Phacopsis'' used to distinguish species from each other include the shape of their spores, and the colour and reaction of the hypothecium (a tissue layer under the spore-bearing

hymenium The hymenium is the tissue layer on the hymenophore of a fungal fruiting body where the cells develop into basidia or asci, which produce spores. In some species all of the cells of the hymenium develop into basidia or asci, while in others some ...

) when

stained A stain is a discoloration that can be clearly distinguished from the surface, material, or medium it is found upon. They are caused by the chemical or physical interaction of two dissimilar materials. Accidental staining may make materials app ...

using an iodine–starch test. Since ''Phacopsis'' fungi are usually restricted to living on hosts belonging to a single phylogenetic

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

, the identity of the host lichen is another diagnostic

character Character or Characters may refer to: Arts, entertainment, and media Literature * ''Character'' (novel), a 1936 Dutch novel by Ferdinand Bordewijk * ''Characters'' (Theophrastus), a classical Greek set of character sketches attributed to The ...

used to identify species.

Systematics

''Phacopsis'' 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 ...

by French

mycologist Mycology is the branch of biology concerned with the study of fungus, fungi, including their genetics, genetic and biochemistry, biochemical properties, their Taxonomy (biology), taxonomy and ethnomycology, their use to humans, including as a so ...

in 1852 with multiple species originally classified in genus ''

Abrothallus ''Abrothallus'' is a genus of lichenicolous fungi. It is the only genus in the monotypic family Abrothallaceae, which itself is the sole taxon in the order Abrothallales. Taxonomy The genus was circumscribed by Italian botanist Giuseppe De Nota ...

''. Tulasne included three species: ''P. clemens'', ''P. varia'', and ''P. vulpina''. The last-mentioned species was later selected as the type species by Frederic Clements and Cornelius Shear (1931), and by

John Axel Nannfeldt John-Axel Nannfeldt (baptized ''Johan Axel Frithiof Nannfeldt''), born 18 January 1904 in Trelleborg and deceased 4 November 1985 in Uppsala, was a Swedish botanist and mycologist. Nannfeldt studied natural history at the University of Uppsal ...

(1932). Of the other two species originally included in ''Phacopsis'' by Tulasne, ''P. clemens'' has since been referred to the genus ''

Arthonia ''Arthonia'' is a genus of lichens in the family Arthoniaceae. It was circumscribed by Swedish botanist Erik Acharius in 1806. It is a genus of thin crustose lichen of widely varying forms, commonly called comma lichens.Field Guide to Californi ...

'', while ''P. varia'' is now known as ''

Opegrapha physciaria ''Opegrapha'' is a genus of lichenized fungi in the family Opegraphaceae ''Opegraphaceae'' is a family of lichen-forming and lichenicolous fungi in the order Arthoniales. It was originally proposed by German lichenologist Ernst Stizenberger in ...

''. In 1988, Dagmar Triebel and Gerhard Rambold proposed that ''Phacopsis'' should be considered

synonymous A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...

with '' Nesolechia'' (another genus of lichenicolous fungi in the Parmeliaceae), owing to similarities both in the structure of their apothecia and the characteristics of their hymenia. This proposed synonymy, however, was not accepted by several authors in the years following, until 1995 when Triebel, Rambold, and John Elix showed that the supposed differences that separated the two genera were not consistent. Following this, Ove Eriksson and

David L. Hawksworth David Leslie Hawksworth (born 1946 in Sheffield, UK) is a British mycologist and lichenologist currently with a professorship in the Universidad Complutense de Madrid in Madrid, Spain and also a Scientific Associate of The Natural History Museum ...

used an expanded generic concept of ''Phacopsis'' ('' sensu lato'') in the next update of their regular publication on

ascomycete Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota, forms the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It is the largest phylum of Fungi, with over 64,000 species. The defi ...

systematics, ''Systema Ascomycetum''.

Molecular phylogenetic Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

analysis published in 2015 demonstrated that the group of species then considered to be members of ''Phacopsis'' actually comprised three distinct lineages, representing three genera: ''Phacopsis'', ''Nesolechia'', and the newly circumscribed ''

Raesaenenia ''Raesaenenia'' is a fungal genus in the large family Parmeliaceae. It is a monotypic genus, containing the single lichenicolous fungus ''Raesaenenia huuskonenii'', which parasitises lichens of genus ''Bryoria'' in the Northern Hemisphere. Tax ...

''. In 2017, Divakar and colleagues used a then-recently developed "temporal phylogenetic" approach in an attempt to make family- and genus-level classification more consistent with evolutionary history. They proposed to synonymize genus ''Nesolechia'' with ''

Punctelia ''Punctelia'' is a genus of foliose lichens belonging to the large family Parmeliaceae. The genus, which contains about 50 species, was segregated from genus ''Parmelia'' in 1982. Characteristics that define ''Punctelia'' include the presence of ...

'', and ''Raesaenenia'' with ''

Protousnea ''Protousnea'' is a genus of lichenised ascomycetes in the large family Parmeliaceae. It contains two accepted species. ''Protousnea'' species have a fruticose growth form, similar to beard lichens (genus ''Usnea''). The genus is endemic to south ...

'', because the lichenicolous genera originated relatively recently and fell under the timeframe threshold for genus level. This proposed synonymy was not accepted in a later critical analysis of the temporal phylogenetic approach for fungal classification. In a 2018 review of taxonomic developments in the family Parmeliaceae, the authors recommended not synonymizing ''Nesolechia'' and ''Phacopsis'', suggesting that the separation between these two genera has not yet been sufficiently established. The higher-level classification of ''Phacopsis'' has changed several times in its taxonomic history. It has been placed in the order Arthoniales, in the families

Graphidaceae The Graphidaceae are a family of lichens in the order Ostropales. Distribution and ecology The vast majority of Graphidaceae species are restricted to the tropics. Most Graphidaceae species are epiphytic (i.e. they grow only on plants). Gener ...

, and the

Acarosporaceae The Acarosporaceae are a family of fungi in the order Acarosporales. Members of this family have a widespread distribution, and are mostly lichenized with green algae. According to a 2021 estimate, the family contains 11 genera and about 260 spe ...

. Using

electron microscopy An electron microscope is a microscope that uses a beam of accelerated electrons as a source of illumination. As the wavelength of an electron can be up to 100,000 times shorter than that of visible light photons, electron microscopes have a hi ...

, Josef Hafellner examined the

asci ASCI or Asci may refer to: * Advertising Standards Council of India * Asci, the plural of ascus, in fungal anatomy * Accelerated Strategic Computing Initiative * American Society for Clinical Investigation * Argus Sour Crude Index * Association of ...

(spore-bearing cells) of the type species ''P. vulpina'', showing them to be similar to those commonly found in members of the Lecanoraceae, and so he considered the genus most appropriately classified in this family. This familial placement, however, was not corroborated in Triebel and colleagues' 1995 review and revision of the genus. Molecular phylogenetic analysis eventually revealed its true phylogenetic placement in the family Parmeliaceae. This relationship is an example of adelpho-parasitism, in which the host species is closely related to the parasite; this type of relationship is fairly common in the Lecanorales. The genus ''Protousnea'' has a sister taxon relationship with ''Phacopsis''. It has been estimated that the lichenicolous ''Phacopsis'' diverged evolutionarily from the lichen-forming ''Protousnea'' during the Miocene (23.03 to 5.333

mya Mya may refer to: Brands and product names * Mya (program), an intelligent personal assistant created by Motorola * Mya (TV channel), an Italian Television channel * Midwest Young Artists, a comprehensive youth music program Codes * Burmese ...

Description

All species are endokapylic, meaning they possess a thallus in which no morphologically distinct lichenized structure is formed. Their apothecia are circular to irregular in shape, and may be dispersed or aggregated. The excipulum (the outer margin of the apothecium) range from colourless to blackish-brown, and often comprises "a few rows of cells which may be difficult to recognize". The hypothecium (a layer of dense hyphal tissue just below the

) is colourless to blackish-brown. In some species, the hyphae in the hypothecium have a violet

staining Staining is a technique used to enhance contrast in samples, generally at the microscopic level. Stains and dyes are frequently used in histology (microscopic study of biological tissues), in cytology (microscopic study of cells), and in the ...

reaction with an iodine–starch test; this characteristic can be used to distinguish between some species. The hymenium is colourless, pale brownish, or pale

olivaceous Olive is a dark yellowish-green color, like that of unripe or green olives. As a color word in the English language, it appears in late Middle English. Shaded toward gray, it becomes olive drab. Variations Olivine Olivine is the typical ...

. Asci are more or less club-shaped, and contain eight spores. They are surrounded by a thin outer amyloid wall layer and a thicker, non-amyloid inner wall layer; a non-amyloid zone rests above the axial body of the

ascus An ascus (; ) is the sexual spore-bearing cell produced in ascomycete fungi. Each ascus usually contains eight ascospores (or octad), produced by meiosis followed, in most species, by a mitotic cell division. However, asci in some genera or s ...

. The ascospores are colourless, lack septa, and have smooth walls with occasional thickening at either end. The spores have a range of shapes; depending on the species, the following shapes have been recorded:

ellipsoid An ellipsoid is a surface that may be obtained from a sphere by deforming it by means of directional scalings, or more generally, of an affine transformation. An ellipsoid is a quadric surface; that is, a surface that may be defined as the ...

, ovoid (egg-shaped), fusiform (spindle-shaped), lemon-shaped, falciform ( sickle-shaped), fabiform (bean-shaped), and partly curved. The pycnidia of ''Phacopsis'' are immersed in the thallus of the host. Pycnospores have a

bacilliform A bacillus (), also called a bacilliform bacterium or often just a rod (when the context makes the sense clear), is a rod-shaped bacterium or archaeon. Bacilli are found in many different taxonomic groups of bacteria. However, the name ''Bacillu ...

shape.

Distribution

Members of the host family, Parmeliaceae, are found worldwide and the family has centres of distribution in Asia and in the Southern Hemisphere; ''Phacopsis'' probably occurs wherever the host does. A 1995 survey of ''Phacopsis'' accepted 13 taxa (eight species and several varieties) found on 41 host species on 20 genera. Little is known about several ''Phacopsis'' species, and some have only been found at their type locality. The most southernly distributed member of the genus is ''Phacopsis usneae'', known to occur only in southern Chile and Antarctica. Like many lichenicolous fungi, ''Phacopsis'' species are usually restricted to living on a host belong to a single phylogenetic

. In 2002,

André Aptroot André Aptroot (Heemskerk, 1961) is a Dutch mycologist and lichenologist. In 1993 he did his PhD at the University of Utrecht under the supervision of Robbert Gradstein (nl). His dissertation was titled "Systematic studies on pyrenocarpous li ...

and Triebel suggested a possible close phylogenetic relationship between ''Paraparmelia'' and ''

Xanthoparmelia ''Xanthoparmelia'' (commonly known as green rock shields or rock-shield lichens) is a genus of foliose lichen in the family Parmeliaceae.Field Guide to California Lichens, Stephen Sharnoff, Yale University Press, 2014, ''Xanthoparmelia'' is syn ...

'', since '' Phacopsis australis'' was noted to grow on representatives from both of those lichen genera. Since then,

molecular phylogenetic Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

analysis has demonstrated that they are equivalent, and ''Paraparmelia'' is now placed in synonymy with ''Xanthoparmelia''.

Species

''Phacopsis'' species are distinguished from each other by the characteristics of their ascospores, the colour and amyloid reaction of the hypothecium, and the identity of their host. According to Index Fungorum, 33 taxa have been described under the name ''Phacopsis'' (28 species and 5 varieties). A recent (2022) estimate places 10 species in genus ''Phacopsis''. The following list of ''Phacopsis'' species indicates its name, taxonomic authority ( standard abbreviations are used) and year of publication, type locality, and host species (or genus). *'' Phacopsis australis'' – southern Africa; host=''

'' *'' Phacopsis cephalodioides'' – Denmark; host=''

Hypogymnia physodes ''Hypogymnia physodes'', commonly known as the monk's-hood lichen, is a species of foliose lichen in the family Parmeliaceae. It is a common and widespread species in boreal forest, boreal and temperate forests of the Northern Hemisphere. It has ...

'' *'' Phacopsis lethariellae'' –

Canary Islands The Canary Islands (; es, Canarias, ), also known informally as the Canaries, are a Spanish autonomous community and archipelago in the Atlantic Ocean, in Macaronesia. At their closest point to the African mainland, they are west of Morocc ...

; host='' Lethariella intricata'' *'' Phacopsis oroarcticae'' – Severnaya Zemlya; host=''

Brodoa oroarctica ''Brodoa'' is a genus of three species of foliose lichens in the family Parmeliaceae. The genus, circumscribed in 1986 by Trevor Goward, is named in honour of lichenologist Irwin Brodo Irwin M. Brodo (born 1935) is an emeritus scientist at the C ...

'' *'' Phacopsis prolificans'' – Japan; host=''

Platismatia interrupta ''Platismatia interrupta'' is a species of foliose lichen in the family Parmeliaceae. Found in southern Russian Far East, and Japan, it was formally described as a new species in 1968 by William and Chicita Culberson. The species epithet '' ...

'' *'' Phacopsis rufa'' – Australia; hosts=''

Cetrelia ''Cetrelia'' is a genus of leafy lichens in the large family Parmeliaceae. They are commonly known as sea-storm lichens, alluding to the wavy appearance of their lobes. The name of the genus, circumscribed in 1968 by the husband and wife ...

'' and ''

'' *'' Phacopsis thallicola'' – New Zealand; hosts='' Cetrelia sanguinea'', ''

Flavoparmelia caperata ''Flavoparmelia caperata'', the common greenshield lichen, is a foliose lichen that grows on the bark of trees, and occasionally on rock. Identification ''Flavoparmelia caperata'' is a medium to large foliose lichen that has a very distinctive ...

'', '' Flavoparmelia praesignis'', '' Parmotrema eurysacum'', '' Rimelia cetraria'' *'' Phacopsis usneae'' –

Kerguelen Islands The Kerguelen Islands ( or ; in French commonly ' but officially ', ), also known as the Desolation Islands (' in French), are a group of islands in the sub-Antarctic constituting one of the two exposed parts of the Kerguelen Plateau, a large ...

; host=''

Usnea trachycarpa ''Usnea'' is a genus of mostly pale grayish-green fruticose lichens that grow like leafless mini-shrubs or tassels anchored on bark or twigs.Field Guide to California Lichens, Stephen Sharnoff, Yale University Press, 2014, The genus is in the f ...

'' *'' Phacopsis vulpicidae'' –

Renchinlkhümbe Renchinlkhümbe ( mn, Рэнчинлхүмбэ) is a '' sum'' of Khövsgöl Province in Mongolia. The area is about , of which are pasture and 35% are forest. In 2000, the ''sum'' had 4284 inhabitants, mainly Darkhad. The ''sum'' center, official ...

(Mongolia); host='' Vulpicida'' *'' Phacopsis vulpina'' – France; host=''

Letharia ''Letharia'' is a genus of fruticose lichens belonging to the family Parmeliaceae. There were historically two species of ''Letharia'': '' L. vulpina'' and '' L. columbiana''. Recent molecular sequence studies published in 2016 confirm at least ...

'' In 1995, Triebel and colleagues described ''Phacopsis menegazziae'' for a Nepalese fungus similar to ''Phacopsis oxyspora'', but with smaller spore dimensions and growing on the host ''

Menegazzia terebrata ''Menegazzia terebrata'' is a species of foliose lichen found scattered across many continents, including North America, South America, Europe, Africa, and Asia. Taxonomy This species was first described as ''Lobaria terebrata'' by Georg Fran ...

''. Paul Diederich synonymised ''P. menegazziae'' with ''P. oxyspora'' in 2003, based on specimens he found growing on ''Menegazzia'' with ascospores similar in size to typical ''P. oxyspora''. ''Phacopsis oxyspora'' is now '' Nesolechia oxyspora'' , the type species of ''Nesolechia''. Several species formerly placed in ''Phacopsis'' have since been transferred to other genera. These include: *''Phacopsis crustulosae'' now '' Gyrophthorus crustulosae'' *''Phacopsis doerfeltii'' now '' Nesolechia doerfeltii'' *''Phacopsis ericetorum'' now ''

Rhymbocarpus ericetorum ''Rhymbocarpus'' is a genus of lichenicolous (lichen-dwelling) fungi in the family Cordieritidaceae. It has 10 species. The genus was circumscribed by German mycologist Friedrich Wilhelm Zopf in 1896, with '' Rhymbocarpus punctiformis'' assigne ...

'' *''Phacopsis falcispora'' now '' Nesolechia falcispora'' *''Phacopsis huuskonenii'' now '' Raesaenenia huuskonenii'' *''Phacopsis lesdainii'' now '' Echinodiscus lesdainii'' *''Phacopsis macrospora'' now ''

Cercidospora macrospora ''Cercidospora macrospora'' is a species of lichenicolous fungus in the genus '' Cercidospora'' but it has not been assigned to a family. It is known from the northern hemisphere. Known host species include lichen of the genus ''Lecanora ''L ...

'' *''Phacopsis muelleri'' now '' Calloria muelleri'' *''Phacopsis mulleri'' now '' Skyttella mulleri''

References

{{Taxonbar, from=Q127256 Parmeliaceae Lecanorales genera Lichenicolous fungi Taxa described in 1852 Taxa named by Edmond Tulasne