A revision of the epiphytic species of the Lecanora subfusca group (Lecanoraceae, Ascomycota) in the Czech Republic

During a revision of epiphytic species of the Lecanora subfusca group in the Czech Republic, nine taxa were recorded. Lecanora cinereofusca, although reported for the first time from the country here, is considered to be extinct, as is L. horiza. Lecanora circumborealis has been excluded from the list of Czech lichens. Lecanora rugosella and L. subrugosa respectively are regarded as extreme morphological forms of L. chlarotera and L. argentata, ecologically derived through nutrient enrichment (eutrophication). Lecanora laevis is regarded as a morphotype of L. horiza. An identification key is provided. The importance of the amphithecium and cortex type as taxonomic characters is discussed in detail. Several new secondary metabolites belonging to the terpenoids, discovered during an investigation of lichen compounds, proved to be taxonomically important. The abundance of L. allophana and L. chlarotera has decreased during the second half of the 20th century, but L. pulicaris has expanded. The main reasons for these changes are air pollution and acidification of substrata; L. pulicaris, for example, formerly a predominant lichen on acid-barked trees, today grows mainly on trees with slightly acidic or subneutral bark.