Fascinating Lichens of Sri Lanka

Usnea
Beard lichens, Old man’s beard
Lecanorales Usneaceae
c.500
Usnea is a cosmopolitan genus found in cool, wet, temperate areas and montane
rainforests in tropical and sub tropical areas. Species of Usnea are collectively
referred as old man’s beard. This is a very large genus of conspicuous fruticose
lichens comprising more than 500-600 species. It is found on rocks, bark, wood,
canopy branches, twigs, shrubs, and soil in a very wide range of habitats. Also
it is noteworthy that some species have been observed on sign boards, power
poles, fence posts and grave tombs etc. invading man-made structures in moist,
humid high elevation areas.
This genus is under revision at the moment due to the molecular data change
causing the delimitation of species within the genus. Many species which were
known under one common name have been identified as consisting distinct
lineages. In Sri Lanka, the genus remains very poorly known.
Lobariaceae
Fo
C
Sticta weigelii
Description Foliose, dark brownish black when dry, becomes reddish chocolate
brown when wet, broadly rounded lobes which resembles an arrangement of
cabbage leaves. Lobe margins are densely isidiate. Isidia are small. The lower
surface is dark brown to pinkish brown. Cyphellae are scattered. Apothecia are
reddish and numerous.
Status Common species. Can be easily recognized due to its reddish apothecia
and broad brown lobes.
In montane forests of the central highlands, Usnea is a dominant component
of the forest canopy, which is one of the least studied habitats in Sri Lanka.
Recent work carried out by Weerakoon and Aptroot (2014) recorded six new
Usnea species for Sri Lanka including four species that are new records for the
Indian subcontinent. Around 15-20 species are known from Sri Lanka, that need
taxonomic revision using molecular and chemical data.
Usnea can be easily distinguished from similar genera by having a characteristic
central cord. Usnea is one of the most commercially important lichens because
of its use in the production of usnic acid, an effective antibiotic against certain
bacteria. Some species of Usnea are used in dye-making and are also used to
brew beer (in Mexico). Usnea species are also important to wildlife as both food
and nesting material.
Usneaceae
Habitat Mostly seen in humid high elevation forest areas. However, this is a rare
species occurring on high elevation rainforests and montane forests. When the
thallus is young, it is not easy to spot among mosses.
Locations Horton Plains (common), Knuckles upper montane forest- common
in Kalupahana, and Gombaniya areas, Hakgala strict nature reserve and
Pidurutalagala peak.
Apothecia lecanorine, lateral, subterminal or terminal, disc pruinose, concave
to plane, usually pale lemon green; Asci: 8-spored; Spores: colourless, simple
ellipsoid.
Chemistry Usnic acid present in cortex of all species KC+ dark yellow, medulla
with a varied chemistry. Many different chemotypes are present even within
the same species, therefore TLC is essential for the correct identification of the
species.
156 Fascinating Lichens of Sri Lanka
Fascinating Lichens of Sri Lanka 157