Ribosomal DNA and β-tubulin data do not support the separation of the lichens Usnea florida and U-subfloridana as distinct species

The lichens Usnea florida and U. subfloridana have since long been recognised as distinct species. They show many similarities in morphology, but have different reproductive strategies. Usnea florida is always provided with many apothecia and produces no specialised asexual propagules. Usnea subfloridana has soralia, isidiomorphs and occasionally apothecia. Phylogenetic analyses based on continuous sequences of the ITS and LSU regions of the nuclear ribosomal DNA and the gene coding for beta-tubulin, show that specimens of the two species form one monophyletic group of intermixed specimens, and not two groups corresponding to morphology, which Would have been expected if two species were at hand. The 'species pair' concept in lichenology is discussed. Other Usnea species included in the study are: U. articulata, U. barbata, U. ceratina, U. filipendula. U. hirta, U. rigida and U. wasmuthii.