Toninia squalida
Toninia squalida is a species of lichen in the family Ramalinaceae. It forms small brown scale-like structures that often merge into crusts, typically growing on calcareous rocks or base-rich soils in upland and arctic regions. The species was first described in 1810 by the Swedish lichenologist Erik Acharius as Lecidea squalida, and was transferred to the genus Toninia by Abramo Bartolommeo Massalongo in 1852. Found across the Northern Hemisphere from temperate mountains to arctic zones, it is a scarce alpine species in Britain, mainly recorded from the Scottish Highlands.
Taxonomy
Toninia squalida was first described scientifically in 1810 by the Swedish lichenologist Erik Acharius under the name Lecidea squalida. In his protologue, Acharius characterised the species by its unequal blackish-grey to brownish granular crust with scattered marginal apothecia, these confluent into irregular black conglomerations with white interiors. He cited previous references by Schleicher and noted its occurrence in the Alps and Switzerland on Schleicher's authority. Acharius distinguished L. squalida from the closely related Lecidea miscella and Lecidea conglomerata, noting differences in crustal morphology, colour, and the nature of the apothecial structure. He observed that whilst the powdery crust seldom forms a distinct thallus as in Lecidea miscella, it can nonetheless be granular and uneven,, and range from green to ashen-grey or blackish in colour.Abramo Bartolommeo Massalongo reclassified the species in Toninia in 1852 to give it the binomial name by which it is now known. Massalongo established Toninia as a new genus to accommodate species previously placed in Lecidea and Biatora that shared distinctive characteristics, including solid, plane apothecia with a prominent margin, and ascospores that are oblong to somewhat club-shaped with eight spores per ascus. In describing Toninia squalida, Massalongo characterised it by its grey-brown to olivaceous-grey thallus that is whitish below, cartilaginous, and squamulose to lobate with a wrinkled to surface bearing scattered. He noted the black apothecia with white interiors occurring singly or confluently, with prominent flat margins. Massalongo reported collecting the species on rocks covering an old wooden roof in Verona, and mentioned it had been recorded on Monte Baldo.
Description
The thallus of Toninia squalida is composed of small, scale-like units to about 3 mm across that often multiply and coalesce into a more or less continuous crust. Individual squamules are shallowly concave to slightly convex. Their upper surface is brown to dark brown, sometimes with a greyish cast; it is matte rather than frosted and may show fine cracking. The margins are the same colour as the surface and there are no pseudocyphellae. In section, the upper is 25–100 micrometres thick and includes a 20–30 μm ; calcium oxalate crystals are absent. The lower cortex is pale brown and only weakly developed. The forms a patchy, discontinuous layer, and the medulla lacks crystals.The fruiting bodies are up to 1.5 mm in diameter, with that are flat to slightly convex and again not pruinose. The is indistinct: the rim is dark brown and may appear greenish, while the inner part is pale brown to colourless. Routine spot tests on these pigments give K– reactions; the rim may turn violet with the N test, and the is K– but N+. The spore-bearing layer is clear and 70–80 μm tall, underlain by a colourless to pale brown.
Ascospores are needle-like, measuring 17–45 × 3–5 μm, and are divided by 3–7 cross-walls. No secondary metabolites were detected using thin-layer chromatography.
Habitat and distribution
Toninia squalida is chiefly terricolous, favouring base-rich soils and humus; it also occurs on weathered, slightly calcareous or other base-rich siliceous rocks in dry, upland situations. Young thalli are often intermixed with cyanobacteria or nest within small cyanolichen patches.In Britain it is a scarce alpine species of calcareous rocks, typically nestled among mosses along damp seepage lines; confirmed records are concentrated in the Scottish Highlands, including Ben Lawers and Caenlochan.
Globally the species ranges broadly across the Northern Hemisphere, extending from temperate uplands into arctic and subarctic zones. It is listed across numerous sectors of the Pan-Arctic, and North American records include Alaskan sites where it grows on soil over rock.