Chemical variation of Usnea longissima Ach. in the central Oregon Coast Range

Abstract

The lichenized ascomycete Usnea longissima occurs in cool forests with coastal climates in Europe, Asia and North America and is threatened throughout its range. The Pacific Northwest region of North America is considered a stronghold of this species. While many studies have focused on the ecology of U. longissima, knowledge of the secondary chemistry of U. longissima is sparse for the region. The objectives of this study were to analyze collections of U. longissima for chemotypic variation using thin-layer chromatography and to examine ecological and geographic patterns of chemotype variation within the central Oregon Coast Range. Three major chemotypes were found within the study area with some additional chemotypic variation documented throughout the global range of U. longissima . The most common chemotype (chemotype 1: usnic, barbatic and norbarbatic acids) accounted for 70.9% of samples, with the other 2 chemotypes accounting for 24% (chemotype 2: usnic and diffractaic acids) and 4.2% (chemotype 3: usnic and a minor unknown acid) of samples. Chemotype 2 generally occurred farther west and at higher elevations than chemotype 1. Different chemotypes may deserve protection to ensure the persistence and genetic variation of U. longissima throughout its current range.