Three hypotheses of the phylogeny of the lichenized Parmeliaceae are constructed, using sequences of the nuclear ribosomal gene
cluster (SSU, ITS, 5·8S rDNA) from Bryoria capillaris, Cetraria islandica, Evernia prunastri, Hypogymnia physodes, Parmelia saxatilis,
Platismatia glauca, Pleurosticta acetabulum, Usnea florida, Vulpicida juniperina, V. pinastri and Xanthoparmelia conspersa. The first analysis,
based on SSU sequences, shows the representatives of the Parmeliaceae to form a monophyletic group within the order Lecanorales.
Usnea florida and Bryoria capillaris, sometimes classified in the families Usneaceae and Alectoriaceae, respectively, are also members of
the Parmeliacceae. Cetraria and Vulpicida form a well-supported monophyletic group together with Usnea, but there is little support
for any other groupings within Parmeliaceae. The second analysis is based on ITS an 5·8S sequence data of the representatives of
the Parmeliaceae included in the first analysis, and supports the close relation of Cetraria and Vulpicida. Other groupings are not
supported, and the topology also varies greatly with minor alignment changes. This is attributed to the included taxa being too
distantly related to each other, causing alignment difficulties of the variable ITS region when a relatively small number taxa are
included. It is predicted that a larger sample of phylogenetically intermediate taxa will overcome this problem. When combining the
two datasets, the results are similar to the ITS results. The present study is one of the first phylogenetic studies utilizing the
information in more than one gene alone in lichenized ascomycetes.