Usnea fulvoreagens

Usnea fulvoreagens is a species of beard lichen in the family Parmeliaceae. It was first described by Finnish lichenologist Veli Räsänen in 1931 as a variety of Usnea glabrescens. He raised it to distinct species status in 1935. The lichen has a shrubby thallus that is richly branched, and bases that are blackened. The presence of norstictic acid is often used to differentiate this species from other similar species. It has a widespread distribution in Europe.

In 2002, Pekka Halonen and Teuvo Ahti proposed the conservation of Usnea fulvoreagens with a conserved type, to address discrepancies between the original Estonian material and the widely accepted species concept. This proposal, aimed at correcting issues with prior lectotypification attempts by Józef Motyka, which used non-original Finnish material now located in Russia, was initially met with ambiguity due to morphological differences among specimens on the proposed type sheet. After further clarification by Ahti, identifying a specific specimen as the conserved type, the Nomenclature Committee for Fungi supported the proposal more than two decades later, recognising the need for consistency in the taxonomic identification of this species.