Chapsa
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| Chapsa | |
|---|---|
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Fungi |
| Division: | Ascomycota |
| Class: | Lecanoromycetes |
| Order: | Graphidales |
| Family: | Graphidaceae |
| Genus: | Chapsa A.Massal. (1860) |
| Type species | |
| Chapsa indicum A.Massal. (1860) | |
Chapsa is a genus of lichens in the family Graphidaceae. These lichens form thin, grey-whitish to pale olive crusts on tree bark and are characterized by fruiting bodies that start as slits but expand into round to angular discs level with the surface, each bordered by a pale rim. The genus has a pantropical to warm-temperate distribution, growing on shaded bark in humid lowland or foothill rainforests, with over 60 species that often serve as indicators of undisturbed forest habitats.
The genus was circumscribed by the Italian lichenologist Abramo Bartolommeo Massalongo in 1860.[1] The genus was resurrected by Frisch and colleagues in 2006 to include species earlier classified in Chroodiscus, Myriotrema, Ocellularia, and Thelotrema.[2]
Description
Chapsa forms a thin, grey-whitish to pale olive crust (thallus) lacking a true cortex. Its ascomata are chroodiscoid: they start as slits but expand into round to angular discs level with the thallus, each bordered by a pale, partly free excipulum armed with tiny periphysoids. The clear hymenium has branched "Chapsa-type" paraphyses, is iodine-negative (I–), and houses eight hyaline ascospores that are transversely 3–15-septate; a few species develop longer, somewhat muriform spores. Most lack secondary metabolites, though some produce norstictic acid or stictic acid that tint the discs orange-brown.[3]
Molecular work has split off allied genera (e.g., Astrochapsa, Pseudochapsa, Nitidochapsa) for lineages with divergent chemistries or spores, yet all share the chroodiscoid discs, periphysoids and branched paraphyses diagnostic for the group. Over 60 species remain in Chapsa, and discoveries such as C. murioelongata show that diversity is still being revealed.[4]