Toninia


Toninia is a genus of lichen-forming fungi in the family Ramalinaceae. The genus contains about 70 recognised species that are distributed worldwide, with many found in arctic and alpine environments as well as arid regions. These lichens are characterised by their often reduced or scale-like thalli and distinctive black apothecia that typically become convex with age and contain needle-shaped ascospores. Toninia species primarily grow on soil, rocks, and other mineral substrates, and are distinguished from related genera by their spore-producing structures and chemical reactions to standard lichen identification tests.

Taxonomy

The genus was circumscribed by the Italian lichenologist Abramo Bartolommeo Massalongo in 1852, with Toninia cinereovirens assigned as the type species. In his original Latin description, Massalongo established the new genus to accommodate lichens with distinctive characteristics that set them apart from related groups. He described Toninia as having solid, flattened fruiting bodies with a distinctive rim around the edge, and a that opens from an initially narrow opening to become wider and more exposed. The thallus was noted to be crusty and scaly, often growing in overlapping patches or forming distinct. Massalongo distinguished his new genus from similar groups like Lecidea and Baeomyces, noting that while Toninia species might resemble some members of these genera, they have unique structural features that warranted separate classification. The genus name honours Carlo Tonini, whom Massalongo described as a celebrated chemist and distinguished cultivator of lichenology.

Description

The thallus of Toninia is often reduced or even absent; when present it is usually, meaning it is made up of small, scale-like pieces that can proliferate and merge into an almost continuous crust. In some species the surface becomes nodular or. The upper ranges from poorly to well developed and may carry a thin ; it lacks surface crystals and shows no fissures or pseudocyphellae. A lower cortex is weak or missing. The green-algal partner is ; that is, it consists of simple, spherical green cells, arranged either in a continuous band beneath the cortex or in scattered patches. The medulla typically lacks crystals.
Fruiting bodies are apothecia that are black and not . They are usually flat when young but commonly become convex with age. A is lacking. Instead, the apothecium has a that is initially raised and clear-cut but is often overgrown and excluded later. Microscopically, this exciple is built from radiating, thick-walled, glue-bound hyphae whose cell cavities are rounded to narrowly cylindrical; the inner part is colourless, while the outer edge is dark brown. These tissues lack crystals and have characteristic reactions to standard chemical spot tests: K negative; N negative or, more typically, N+ owing to a pigment sometimes termed "Bagliettoana-green". The is usually olive to green, rarely brown or colourless, also without crystals, K– and usually N+ violet. The hymenium turns I+ with iodine, whereas the is colourless to dark brown and contains no crystals. The consists of straight paraphyses that are unbranched or only sparsely branched and sometimes interlinked; they are not cemented together and have thin walls, with the tip cell distinctly swollen and capped by a gelatinous pigment dome.
The asci are of the Bacidia-type: club-shaped, eight-spored, and sheathed in a gelatinous wall that becomes K/I+ blue. Each ascus has a well-developed, iodine-positive with a darker-staining central tube and a pronounced . Ascospores are colourless and smooth, ranging from non-septate to 7-septate; shapes vary from ellipsoidal to narrowly spindle-shaped or needle-like. Asexual structures are pycnidia that appear black and are immersed to slightly protruding; they produce conidia that are rod-shaped to thread-like. In terms of chemistry, the genus is generally poor in distinctive secondary metabolites: at least one species has been reported with terpenoids, and there are occasional reports of stictic acid and/or xanthones in two taxa that likely do not belong in Toninia and may require exclusion.

Species