XVI International Botanical Congess

The identification of species units in lichenized fungi is still based mainly on characters of morphology, anatomy, or chemistry. Nucleic acid sequence data are now included and they are becoming increasingly important to test traditional species concepts. Results focusing on species pairs indicate that there are probably many more species of lichens than expected before, including clonal, asexual species. The occurrence of such cryptic species raises the question how they should be treated in applied studies and in taxonomy. Different rates of base substitutions are observed within closely related species-groups of mycobionts. The significance of these differences for the species concept is discussed. Preliminary results from experiments with crustose lichens under varying ecological conditions are presented.