Phylogenetic relations of European shrubby taxa of the genus Usnea

This study focuses on European Usnea species with sorediate shrubby thalli, with the aim to evaluate the morphological and chemical separation of species in the light of molecular data. Twenty-two Usnea species, including widely distributed taxa such as U. diplotypus, U. fulvoreagens, U. glabrescens, U. lapponica, U. subfloridana, U. substerilis and U. wasmuthii, were included in the study using Bayesian and maximum parsimony analyses of nuclear ITS and beta-tubulin sequences. The analyses showed that: 1) most taxa that are morphologically well delimited are also distinct by means of molecular characters, 2) shrubby taxa in the section Usnea that are difficult to determine by traditional characters form a group of closely related but still genetically distinct entities, except U. diplotypus and U. substerilis which appear to be polyphyletic. The branch lengths differed largely between two parts of the ITS tree (sections Usnea and Ceratinae). Usnea intermedia is proposed as the sexually reproducing counterpart for the sorediate U. lapponica. Additionally, some new chemotypes of Usnea species were determined.