Cladoniaceae is one of the largest and most diverse families of lichens. It includes about 500 species. The species comprise significant components of numerous terrestrial ecosystems around the world. In addition, Cladoniaceae has proved to be an exceptionally favored host for numerous, poorly known lichenicolous fungi. Altogether 83 species of these fungi have been reported to grow on the Cladoniaceae and most are specified to live on single host taxon only. Our goal is to combine the phylogeny of the Cladoniaceae with complete chemical and distributional data, screen the associated fungi, and produce the first inclusive phylogeny of the latter. This data will be used in studying coevolution of the partners, specificity, evolution of different life strategies as well as evolutionary timing and biogeographical origin of the diversifications and associations. We will also screen for the suitable DNA barcodes for the species. Hypotheses: We anticipate multiple origins of lichenicolous fungi, partial parallel cladogenesis, and Gondwanan origin for the Cladoniaceae, but current patterns of distribution are probably partly explained by recent dispersal. We also anticipate high host specificity and a correlation between chemical composition of the hosts and associated fungi, and that lichenicolous habit is mostly derived from lichen habit, but that lichenicolous habit has also been commonly lost (instability). Further, we anticipate that the host/parasite association is of ancient origin. The results will provide data for applied research, nature conservation, species monitoring, and screening of biodiversity.