Usnea esperantiana P. Clerc

Nomenclatural data
Candollea 47: 2 (1992).
Morphology
For a detailed description, see Clerc (1992, 2007) and Purvis et al. (1992). Thallus clearly shrubby, erect, 4–6 cm; secondary branches distinctly constricted at their base; base pale to light brownish, never blackened; fibrils present, short and numerous over the whole thallus, terminal branches often twisted, resembling octopus arms; papillae small, scarce; soralia numerous, small or usually large and rounded to irregularly shaped but always without isidiomorphs. Medulla loose.
Medullary chemistry
Chemotype (1) with salazinic (K+ red, Pd+ orange) acid and stictic acid complex together with bourgeanic acid (a fatty acid).
Remarks
Belongs to the U. fragilescens aggregate. Constriction of branches at their base and absence of isidiomorphs on numerous flat soralia are the diagnostic morphological characters while presence of bourgeanic acid is a unique chemical character; identification of the latter is possible, however, only using TLC.
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Ecology and distribution
Europe (map legend)
Corticolous on a large variety of trees and bushes, especially on twigs and thin branches. It has a distinct south european-atlantic distribution (Fos & Clerc 2000). Reported in Europe: Great Britain, France, Ireland, Italy, Netherlands, Portugal, Spain.