Phaeographis

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Template:Short description Template:Automatic taxobox

Phaeographis is a genus of lichen-forming fungi in the family Graphidaceae. It has an estimated 180 species.[1]

Taxonomy

The genus Phaeographis was circumscribed by the Swiss lichenologist Johannes Müller Argoviensis in 1882.[2] However, its taxonomic status was uncertain for many years due to the existence of several earlier generic names that potentially had priority.

In 2007, Robert Lücking and colleagues proposed to conserve the name Phaeographis against six earlier names: Creographa, Ectographis, Flegographa, Hymenodecton, Platygramma, and Pyrographa.[2] They also proposed to conserve Phaeographis dendritica as the type species. This proposal was made to maintain nomenclatural stability, as Phaeographis had become a widely used name representing about 150 species.[2]

The proposal was based on a revised generic concept of Graphidaceae presented by the German lichenologist Bettina Staiger, which for the first time provided a detailed analysis of the taxonomic relationships between genera in the family, using both morphological and molecular data.[2]

In 2010, the Nomenclature Committee for Fungi reviewed the proposal and recommended its acceptance with a strong majority (85.7% in favour).[3] This recommendation effectively conserved the name Phaeographis with P. dendritica as its type species, securing its taxonomic status and preventing the need to transfer numerous species to other genera.[3] This conservation was particularly important because Phaeographis represents the second largest genus in the family Graphidaceae, containing approximately 150 species. The conservation of the name is expected to maintain stability in the taxonomy of this significant group of lichens.[2][3]

Description

The genus Phaeographis consists of crustose lichens, characterised by their thin, often inconspicuous thallus, which adheres closely to the Template:Lichengloss. In European species, the hyphae within the thallus react to iodine staining (I+) by turning blue, indicating the presence of specific starch-like compounds. The Template:Lichengloss, or photosynthetic partner, is a green alga of the genus Trentepohlia, which is common in many lichens.[4]

The reproductive structures of Phaeographis are apothecia, which are fruiting bodies that vary in form from unbranched to branched or star-like (Template:Lichengloss). These structures are Template:Lichengloss, meaning they are elongated and slit-like in appearance. They are typically Template:Lichengloss within the thallus but may protrude slightly. The margin of the thallus surrounding the apothecia is generally inconspicuous, blending into the rest of the lichen surface. The Template:Lichengloss, a layer of tissue surrounding the hymenium (the spore-producing region), is thin and black, and may or may not extend beneath the hymenium. The Template:Lichengloss of the apothecia is expanded and ranges in colour from brown to black. It is often Template:Lichengloss in texture and may be coated with a white powdery substance (Template:Lichengloss).[4]

The internal structure of the apothecia includes a colourless hymenium that does not react with iodine (I–) and contains crystalline inclusions. The Template:Lichengloss, the network of sterile filaments between the spore-producing asci, is composed of unbranched paraphyses. These filaments have Template:Lichengloss (club-shaped) apical cells that are brownish in colour. The asci are of the Graphis-type, containing eight spores each, and do not react with iodine (K/I–).[4]

Template:Lichengloss are initially colourless but soon develop a pale to reddish-brown colouration within the ascus. They are I+ (purple) and are transversely divided into many segments, forming lens-shaped cells. Aphaeographis also reproduces asexually through structures called pycnidia, which produce ellipsoidal conidia. These conidia are typically straight or slightly curved.[4]

Species

File:Phaeographis inusta - Flickr - pellaea.jpg
Phaeographis inusta
File:Phaeographis lyellii Jymm.jpg
Phaeographis lyellii
File:Phaeographis multicolor - Flickr - pellaea.jpg
Phaeographis multicolor

References

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