Lecania is a genus of lichen-forming fungi in the family Ramalinaceae.[ These lichens form thin, crustose lichen growths on various surfaces and produce small disc-shaped fruiting bodies that are typically brown to black in colour. Most species reproduce both sexually through and asexually through tiny reproductive structures, allowing them to spread effectively in their environments.
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Taxonomy
The genus was circumscribed by Abramo Bartolommeo Massalongo in 1853. He assigned Lecania fuscella as the type species.
Description
Lecania forms a crustose thallus—that is, a thin, paint-like growth tightly attached to the substrate. Depending on the species, this crust may be only a fraction of a millimetre thick or develop into a more robust layer that cracks into tiny plates () or wart-like bumps. In a few taxon the surface becomes minutely lobed or covered with powdery reproductive tissues such as soralia or tiny grain-like (, ) that help the lichen spread vegetatively. Colours range from grey-white and pale yellow to deep brown-black; many specimens acquire a frost-like coating of minute crystals called , and some have a dead, transparent film that gives a slightly glazed look. The upper is built of tightly packed fungal cells, though in some species this layer is so saturated with crystals that its cellular structure is obscured. The photosynthesis partner is always a single-celled green alga of the type, which nestles within the medulla just beneath the cortex.
The sexual fruiting bodies are tiny, stalk-less (apothecia) that appear flat when young but often bulge into low domes with age. Measuring roughly 0.4–0.6 mm across (occasionally up to 1 mm), these discs vary in colour from pale brown through orange to almost black and may also carry a dusting of pruina. They are usually rimmed by a thin band of thallus tissue, though this margin can erode in older specimens. Viewed in section, the hymenium (the fertile layer) is colourless but turns blue when staining with iodine. Slender paraphyses thread through the hymenium; their tips often swell or darken, giving a mottling, "piebald" appearance when the disc is wetted. Each ascus ordinarily houses eight colourless (occasionally up to sixteen) that are one- to three-septum, though some species may have spores with as many as seven internal walls. Spores are thin-walled, sausage- to spindle-shaped, and longer examples can curve gently. Asexual reproduction is common on bark-dwelling species: flask-shaped pycnidia produce tiny, curved conidia.
Most Lecania species lack distinctive secondary metabolites, but a few contain the lichen substance atranorin or various unidentified . Pigments within the apothecia sometimes give positive colour reactions with standard chemical spot tests (K or N).
Species
, Species Fungorum (in the Catalogue of Life) accepts 65 species of Lecania.
