Usnea glabrescens

Diane L. Haughland

Usnea glabrescens (Nyl. Ex Vain.) Vain., 1925

Common name	Speckled Beard	Code: USNEGLB
Field Characters	Fruticose, shrub-like chlorolichen. Thallus erect to subpendant, usually to 15 cm long but sometimes exceeding, with stiff, dichotomously divergent branches. Bases black and often with tiny, lens-shaped, longitudinally oriented cracks (seen at 40x magnification). Papillae sparse and inconspicuous to numerous. Cortex thick, medulla thin, axis moderately thick. Soralia conspicuous, distinctly rounded and well delimited, as large as or larger than half the branch diameter, flat to slightly concave or deeply excavate. Apothecia and pycnidia not observed. Isidia absent or rarely present on young and punctiform soralia.
Similar species	U. lapponica: less robust, isidia are unknown, and it has irregular branches and few to no basal cracks. U. substerilis: soralia are at most weakly excavate at maturity. U. subfloridana: has smaller soralia that are less than half the diameter of the stem, with a strongly UV+ blue-white medulla lending to the appearance of a lit Christmas tree under UV, while U. glabrescens soralia may exceed half of stem diameter and the medulla only fluoresces in some areas where exposed.
Ecology	On both deciduous and coniferous trees, mostly detected to date in the boreal forest. Rare in Alberta.
Chemistry	Cortex KC+ yellow, K- or K+ pale yellow, C-, UV- (usnic acid). Medulla K+ yellow to orange, PD+ yellow to orange (norstictic, ± salazinic, ± diffractaic, ± protocetraric (trace) acids; or stictic, norstictic, ± constictic, ± cryptostictic, ± menegazziaic, ± diffractaic acids) or K-, PD-.
Molecular support	Weak at species-level. Clades in a multi-locus phylogeny do not correspond to traditionally circumscribed species (Lucking et al. 2020).
Links	Alberta Biodiversity Browser Consortium of Lichen Herbaria
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