Graphis (lichen) explained

Graphis is a genus of lichen-forming fungi in the family Graphidaceae. Historically, Graphis was used as a broad category for species with colourless, transversely septate ascospores within the Graphidaceae. However, with advances in genetic research, this classification has become more refined. As a result, species previously classified under Graphina have been re-assigned to Allographa or Graphis. The species complex around Graphis scripta has also been recognised, leading to the identification of several new species, many of which may have been previously overlooked.

Description

Genus Graphis includes crustose lichens, which have a crust-like appearance that can range from being fully embedded in the substrate to sitting on the surface. The lichen's symbiotic partner, or, is green algae from the genus Trentepohlia. The (fruiting bodies) of Graphis can also be immersed or superficial. These structures are typically elongated, resembling slits (referred to as), and can be, branched, or star-shaped. The of the apothecium, where spores are released, often remains slit-like or closed. Unlike some lichens, Graphis lacks a, which is a rim of tissue derived from the lichen thallus surrounding the apothecium. Instead, it has a, which is usually black, opaque, and well-developed. This exciple is sometimes marked by longitudinal grooves.

Inside the apothecium, the hymenium (a spore-bearing layer) is colourless and does not react to staining with iodine (I-). Beneath this layer, the can be either pale or dark, and it is relatively thin. The, which supports the developing spores, consists of unbranched filaments called paraphyses. The spore-producing structures, the asci, typically contain up to eight spores. These asci are club-shaped to slightly cylindrical and release their spores through an apical split. The spores themselves are divided by transverse walls (septate) or have a structure (multiple divisions), and they turn violet when stained with iodine as they mature. Initially colourless, these spores may darken to brown if they become over-mature. Graphis also produces conidia, which are asexual spores, within flask-shaped structures called pycnidia. The conidia are usually cylindrical to ellipsoidal and remain colourless.

Chemically, some species of Graphis contain compounds known as β-orcinol depsidones. Additionally, older apothecia in certain species might react with potassium hydroxide solution (K+) to produce a purple colouration, indicating the presence of anthraquinones.

Graphis can be distinguished from the genus Phaeographis by its colourless spores, which may become brown with age. Additionally, in the field, Graphis species may resemble Opegrapha species, but the latter can be differentiated by their distinctively structured asci and spore-bearing tissues.

Habitat and distribution

Graphis has a cosmopolitan distribution, which includes most continents across the world.[1] This includes Florida in North America.[2] Ecologically, Graphis lichens are mostly found growing on bark, though they are occasionally found on rock. The genus is primarily distributed in tropical and subtropical regions, with a few extending into temperate zones.

Species

As accepted by Species Fungorum;[3]

Notes and References

  1. Web site: Graphis Adans., 1763 . www.gbif.org . 6 February 2023 . en.
  2. Seavey . Frederick . Seavey . Jean . The lichen genus Graphis (Graphidaceae) in Everglades National Park (Florida) . The Bryologist . 2011 . 114 . 4 . 764–784 . 10.1639/0007-2745-114.4.764 .
  3. Web site: Graphis - Search Page . www.speciesfungorum.org . Species Fungorum . 6 February 2023.
  4. Zacarias Lepista . André Aptroot . André Aptroot . Five further species of Graphis reported new to Europe from Portugal . . March 2022 . 54 . 2 . 101–106 . 10.1017/S0024282922000093.

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