Astrochapsa
From Wikipedia, the free encyclopedia
| Astrochapsa | |
|---|---|
_Figure_4D.jpg) | |
| Astrochapsa mirabilis | |
Scientific classification  | |
| Kingdom: | Fungi |
| Division: | Ascomycota |
| Class: | Lecanoromycetes |
| Order: | Graphidales |
| Family: | Graphidaceae |
| Genus: | Astrochapsa Parnmen, Lücking & Lumbsch (2012) |
| Type species | |
| Astrochapsa astroidea | |
| Species | |
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See text | |
Astrochapsa is a genus of lichen-forming fungi in the subfamily Graphidoideae of the family Graphidaceae. It has about 30 species. The genus was circumscribed in 2012, with Astrochapsa astroidea assigned as the type species. It was split from Chapsa because members of this genus usually have a densely skinned thallus, apothecial rims that tend to curve back, and spores that are mostly subdistoseptate (septa slightly thickened; cell spaces angular) and non-amyloid.
Astrochapsa was established in 2012 by Sittiporn Parnmen, Robert Lücking, and H. Thorsten Lumbsch during a generic-level reclassification of the thelotremoid graphid lichens based on DNA evidence. Their analyses showed that several species then placed in Chapsa formed a coherent, separate lineage; to reflect that evolutionary split, they erected Astrochapsa and made a series of new combinations into the genus. The type species was set as Astrochapsa astroidea.[1]
In practical terms, the authors narrowed the concept of Chapsa (Chapsa sensu stricto) and diagnosed Astrochapsa by a suite of characters that tend to occur together in this clade. These include a bark crust (thallus) that is often more thickened and with a developed outer skin (a dense cortex), fruiting discs whose rim is commonly turned slightly outward (a recurved margin), and colourless spores that show a faint thickening at the internal walls ("subdistoseptate") and do not turn blue with iodine (non-amyloid).[1]
Parnmen and colleagues also provided a set of formal transfers from Chapsa and related genera into Astrochapsa, anchoring the name in current practice and stabilising usage across subsequent taxonomic work on Graphidaceae.[1]
Description
Astrochapsa species form a crust on bark (the thallus) that is usually well "skinned" with a dense outer layer (a cortex), rather than appearing loose or without a cortex. Their fruiting bodies (apothecia) break through the bark surface and are round to irregular; the inner disc is exposed while the rim is often lobed and commonly bends back slightly (recurved). The rim tissue (the excipulum) is typically brown, and the disc itself can be pale or pigmented. Chemically, many species have no detectable lichen substances, though stictic acid derivatives are frequent in some; this is consistent with the mix of "no substances" versus "stictic acid and relatives" reported for the genus.[1]
Under the microscope, the spores are colourless (occasionally pale brown), with one or more cross-walls, and they are elongated from spindle-shaped to more cylindrical. The septa between the spore cells are slightly thickened and the cell cavities look angular—features described as "subdistoseptate". A standard iodine test on the spore wall is negative (I–), meaning the wall does not turn blue and so is considered non-amyloid. Taken together with a mostly densely corticate bark crust and apothecia with an often recurved margin and usually brown rim, these characters provide a practical diagnosis of the genus.[1]