Gabura

Gabura
Gabura fascicularis from New Zealand
Scientific classification
Domain:	Eukaryota
Kingdom:	Fungi
Division:	Ascomycota
Class:	Lecanoromycetes
Order:	Baeomycetales
Family:	Arctomiaceae
Genus:	Gabura Adans. (1763)
Type species
Gabura fascicularis (L.) P.M.Jørg. (2014)
Species
G. borbonica G. fascicularis G. insignis

Gabura is a small genus of lichen-forming fungi in the family Arctomiaceae. These lichens form low-growing patches that range from thin, crust-like films to small, crumpled cushions, appearing dark olive-green to almost black when dry but swelling like a sponge and becoming softer when wet. They partner with blue-green algae called Nostoc and grow on tree bark or soil, often among mosses, reproducing through tiny disc-shaped fruiting bodies that contain long, multi-celled ascospores.

Taxonomy

Although it was originally circumscribed in 1763 by French botanist Michel Adanson, the name was nomen rejiciendum–it was "suppressed" against the conserved name Collema , and for a long time considered a synonym of Arctomia . ^[1] In 2014, Per Magnus Jørgensen proposed to use the name Gabura for what was then known as Collema fasciculare. ^[2] The name was formally resurrected for use in 2020. Gabura has three species transferred from the genus Arctomia following molecular phylogenetic analysis. ^[3]

Description

Gabura forms low-growing thalli that range from a thin, crust-like film firmly attached to the substrate to small, crumpled cushions whose margins break into indistinct lobes . When dry the surface is a dark olive-green to almost black; in many species it absorbs water like a sponge, swelling noticeably and taking on a softer texture. A true cortex —the protective outer skin seen in many lichens—is poorly developed or absent, so the underlying tissues show through. Some taxa produce powdery patches called soralia, whose yellow- to brown-tinged granules contain both partners of the lichen symbiosis and serve as ready-made propagules for dispersal. ^[4]

Embedded among the fungal threads are clusters of the cyanobacterium Nostoc ; its orangey-green cells, measuring 5–7  micrometres across, sit within a clear jelly that helps the thallus retain moisture. Sexual reproduction, where it occurs, takes place in minute disc-shaped fruit bodies (apothecia) that arise directly from the lobes and remain almost stalkless. These discs lack a distinct rim of thallus tissue and may be flat or gently domed. Inside, slender branched filaments (paraphyses) stand amongst the asci; their tips broaden and darken to brown. Each ascus is of the Trapelia type: it has a thickened apex (the tholus ) that remains colourless in iodine, while the surrounding gelatinous sheath stains blue, and it normally contains eight long, spindle-shaped ascospores divided by multiple cross-walls (septa). ^[4]

Asexual reproduction is achieved through flask-shaped pycnidia sunk in the thallus; these release tiny, rod-shaped conidia. Chemical screening with thin-layer chromatography has so far revealed no secondary metabolites, making the genus unreactive with standard chemical spot test. The combination of a swelling, dark thallus with optional soralia, cyanobacterial photobiont, Trapelia-type asci and multiseptate spores distinguishes Gabura from superficially similar gelatinous crusts in the same habitats. ^[4]

Ecology

Gabura lichens grow on bark (corticolous) or on soil (terricolous), and are often growing amongst moss. ^[4]

Species

• Gabura borbonica (Magain & Sérus.) Magain & Sérus. (2020)
• Gabura fascicularis (L.) P.M.Jørg. (2014)
• Gabura insignis (P.M.Jørg. & Tønsberg) Magain & Sérus. (2020)

References

1. "Record Details: Gabura Adans., Fam. Pl. 2: 6 (1763)". Index Fungorum . Retrieved 17 April 2022.
2. Jørgensen, Per M. (2014). "Taxonomy and nomenclature of Collema fasciculare (L.) G. H. Weber". The Lichenologist. 46 (4): 594. doi:10.1017/s0024282914000140.
3. Magain, Nicolas; Spribille, Toby; DiMeglio, Joseph; Nelson, Peter R.; Miadlikowska, Jolanta; Sérusiaux, Emmanuël (2020). "Phylogenetic evidence for an expanded circumscription of Gabura (Arctomiaceae)". The Lichenologist. 52 (1): 3–15. doi:10.1017/s0024282919000471.
4. Cannon, P.; Coppins, B.; Sanderson, N.; Simkin, J. (2025). Arctomiales: Arctomiaceae, including Arctomia, Gabura and Gregorella (PDF). Revisions of British and Irish Lichens. Vol. 56. pp. 2–3.