A spot test in lichenology is a spot analysis used to help identify lichens. It is performed by placing a drop of a chemical reagent on different parts of the lichen and noting the colour change associated with application of the chemical. The tests are routinely encountered in dichotomous keys for lichen species, and they take advantage of the wide array of lichen products produced by lichens and their uniqueness among taxa. As such, spot tests reveal the presence or absence of chemicals in various parts of a lichen. They were first proposed as a method to help identify species by the Finnish lichenologist William Nylander in 1866.
Spot tests on the foliose lichen Punctelia borreri showing thallus (top) and medulla (bottom). The pinkish-red colour change of the medulla in the C and KC tests indicate the presence of gyrophoric acid, a chemical feature that helps to distinguish it from similar species in the same genus.
Chemical spot tests on the crustose and saxicolous lichen Aspicilia epiglypta
UV-illuminated thallus and apothecia of the crustose lichen Ochrolechia africana; the yellowish colour results from the fluorescence of lichexanthone.
Lichenology is the branch of mycology that studies the lichens, symbiotic organisms made up of an intimate symbiotic association of a microscopic alga with a filamentous fungus. Lichens are chiefly characterized by this symbiosis.
Lichen
Oakmoss (Evernia prunastri)
K S Merezhkovsky Russian Lichenologist (1855–1921)
