Usnea praetervisa (Asahina) P. Clerc
Nomenclatural data
Bibl. Lichenol. 88: 85 (2004).—Usnea comosa ssp. praetervisa Asahina, Lich. Jap. III. Genus Usnea: 95 (1956).—Usnea subfloridana ssp. praetervisa (Asahina) P. Clerc, Lichenologist 32: 83 (2000).
Morphology
For a detailed description, see Clerc (2004b, 2007). Thallus shrubby to subpendent, richly branched; branching mainly isotomic-dichotomous; base blackened, often with transverse annular cracks; fibrils present already on very young branches, acting like diaspores – fibrils are shed leaving small fibercles, while soredia and isidiomorphs may develop inside these fibercles; papillae present, predominantly on main branches; soralia minute, plane, later becoming confluent; isdiomorphs short, numerous on young soralia but present also on mature ones. Cortex rather thick; medulla thin and dense.
Medullary chemistry
Chemotype (1) with norstictic (K+ red, Pd+ yellow to orange) and connorstictic acids.
Remarks
Morphologically rather similar to Usnea subfloridana, however, differences in the way how soralia develop have been noticed (Clerc 2004b). Originally the taxon was described as having only different chemistry (norstictic acid, biosynthetically a distant medullary compound from thamnolic and squamatic acids, which are produced in U. subfloridana).
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Ecology and distribution
Europe (map legend)
Corticolous, on deciduous trees (Crataegus, Quercus) and on Erica (Clerc 2004b). Reported in Europe: France, Portugal, Spain.