Usnea lapponica Vain.

Nomenclatural data
Meddel. Soc. Fauna Fl. Fenn. 48: 173 (1925).—Usnea arnoldii Motyka, Lich. Gen. Usnea Stud. Monogr., Pars Syst. 1: 288 (1936).—Usnea fulvoreagens auct. non (Räsänen) Räsänen
Morphology
For a detailed description, see Halonen et al. (1998, 1999) and Clerc (2007). Thallus shrubby, richly branched; branching mainly anisotomic-dichotomous; branches often with depressions and foveolae; base pale to blackened; fibrils abundant; isidiomorphs always absent; papillae numerous; soralia large, becoming expanded and irregular or bracelet-like, flat to deeply concave, cortex around soralia is often torn. Cortex thin; medulla variable in thickness, loose to dense.
Medullary chemistry
(1) the main chemotype contains salazinic acid (K+ red, Pd+ yellow to orange) with different accessory substances (protocetraric, barbatic, caperatic acids) (Halonen et al. 1998); (2) chemotype with psoromic acid (K–, Pd+ yellow) is the rarest (Halonen et al. 1999); (3) chemotype without medullary compounds (K–, Pd–) is known both in Europe and North America.
In Estonia chemotypes (1) and (3) are reported (n=12 and n=5, respectively) (Tõrra & Randlane 2007).
Remarks
Distinction from closely related taxa see under U. diplotypus.
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Ecology and distribution
Europe (map legend)
Corticolous. Reported in Europe: Austria, Bulgaria, Czech Republic, Estonia, Finland, Germany, Italy, Latvia, Lithuania, Norway, Poland, Romania, Russia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Ukraine.

Estonia
Grows mainly on conifers (on Picea 37% of examined specimens, on Pinus 24%, on other 22%), on Betula (15%) and on lignum (7%). Very frequent in Estonia (53 specimens), found mainly on the northern coast and in south-eastern region of Estonia (Tõrra & Randlane 2007).