Toensbergia
Toensbergia is a small genus of lichen-forming fungi in the family Sporastatiaceae. These lichens form pale, granular crusts on moist soil, mossy rocks, and conifer bark, spreading primarily through powdery particles rather than sexual reproduction. The genus was established in 2013 and named after the Norwegian lichenologist Tor Tønsberg for his work on bark-dwelling lichens.
Taxonomy
The genus was circumscribed by Mika Bendiksby and Einar Timdal in 2013. The genus name honours the Norwegian lichenologist Tor Tønsberg, "in appreciation of his important work on sorediate, corticolous lichens". The type species is Toensbergia leucococca, which was formerly classified in genus Hypocenomyce due to its resemblance to Hypocenomyce xanthococca.Description
Species of Toensbergia spread as pale granular crusts that can merge into extensive patches or, in sheltered spots, develop into slightly raised, scale-like . Fresh material appears grey-white through cream to a faint green tint, depending on moisture and the density of the embedded green algal partner. A separate —the dark fungal fringe that rims many crustose lichens—is usually absent, but some specimens show a bluish-grey to charcoal border where the fungus grows beyond the photosynthetic layer. Asexual propagules dominate: powdery soredia erupt from tiny nipple-like bumps on the surface, while even finer, coral-shaped break away en masse, allowing the lichen to colonise nearby soil, mossy rock, or conifer bark without relying on sexual spores.Sexual structures are rarely observed in this genus; when present, they are in the form of dark red to nearly black apothecia ringed by a conspicuous rim of thallus tissue, sometimes with shallow scallops along the edge. Inside each fruit-body the —the tissue capping the spore layer—is reddish-brown, and the asci are club-shaped, each producing just two exceptionally large spores. These spores follow the Pertusaria pattern: they have walls so thick that two distinct layers are visible under a microscope and remain unpartitioned by internal cross-walls. No separate flask-shaped conidiomata, which many lichens use for asexual conidia, have been found.
All known species synthesise alectorialic acid, a yellow-reacting compound that can be used to help confirm identifications through thin-layer chromatography.