Usnea substerilis

Diane L. Haughland

Usnea substerilis Mot., 1936

Common name	Embossed Beard	Code: USNESUS
Field Characters	Fruticose, shrub-like chlorolichen. Thallus shrubby, with yellowish green divergent branches. Papillae numerous, fibrils short and unevenly distributed. Base blackened or the same color as the thallus. Soralia conspicuous and circular, occasionally irregular, and raised slightly to slightly excavating into the thallus; often dotting the branch tips and encircling them. Isidia rare, only on young soralia. Apothecia and pycnidia not observed.
Similar species	Usnea lapponica is another shrubby, papillate species, but forms deeply excavate soralia and never produces isidia. Usnea subfloridana is similar, but the medulla fluoresces UV+ blue white wherever exposed, giving the impression of string lights on a tree. Usnea substerilis has patches of UV+ medulla only.
Ecology	Common over conifers and especially deciduous trees and shrubs in open to occasionally sheltered inland forests, rare in coastal regions. Widespread across the forested regions of Alberta.
Chemistry	Cortex KC+ yellow, K- or K+ pale yellow, C-, PD-, UV- (usnic acid). Medulla K+ yellow to orange or K-, PD+ yellow to orange or PD- (salazinic, ± protocetraric, ± 4-O-demethylbarbatic, ±norstictic, ±barbatic acids, or no secondary substances.)
Molecular support	Weak at species-level. Clades in a multi-locus phylogeny do not correspond to traditionally circumscribed species. Because of the lack of resolution in a clade of U. lapponica, U. substerilis, U. barbata, and U. intermedia, Mark et al. (2016b) placed U. substerilis in synonymy with U. lapponica. Lucking et al. (2020) similarly found that there was no evidence for the separation of U. lapponica from U. substerilis. However, Clerc & Naciri (2021) conclude that specimens used in these studies were of insufficient quality and thus suggest that the synonymization of U. lapponica and U. substerilis should not be accepted. Synonymy not adopted at this time; no new sequences generated.
Links	Alberta Biodiversity Browser Ways of Enlichenment Photo Gallery
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