Allographa Explained

Allographa is a genus of script lichens in the family Graphidaceae. It has nearly 200 species. Formally circumscribed in 1824 by François Fulgis Chevallier, Allographa was formerly included in Graphis, but was upgraded to generic status in 2018 by lichenologists Klaus Kalb and Robert Lücking, who used molecular phylogenetics analysis to show this group of species to constitute a distinct lineage in the Graphidaceae.

Description

Allographa is characterised by ascomata (fruiting bodies), which are elongated and groove-like in shape. One of its defining features is the generally excipulum, which gives a dark appearance to the fruiting bodies, although some species formerly placed in Hemithecium with uncarbonised (blackened) are also included in this genus.

Allographa typically displays robust and strongly prominent lirellae, often with a massive structure. The are hyaline (colourless) and usually large to very large in size, turning violet-blue when treated with iodine. A key distinguishing feature from Graphis in the strict sense is the strongly gelatinous with thin paraphyses.

While Allographa shares many morphological similarities with Graphis, making clear-cut distinctions challenging, molecular evidence supports its status as a separate genus. Allographa is part of a larger clade within Graphidaceae that includes other lirellate genera such as Diorygma, Glyphis, Pallidogramme, Phaeographis, Platygramme, Platythecium, Sarcographa, Thalloloma, and Thecaria.

The genus encompasses species previously assigned to the Graphis carassensis group and some former Hemithecium species. Notable examples include A. acharii, A. chrysocarpa, A. rhizocola, A. ruiziana, and species related to A. chlorocarpa and A. rufopallida. Despite the morphological overlap with Graphis, advanced techniques such as morphology-based phylogenetic binning have successfully differentiated most Allographa species from Graphis sensu stricto, confirming its status as a distinct genus within the Graphidaceae.

Species

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