| dc.description.abstract | Molecular phylogenetics has revolutionized the taxonomy of crustose lichens and revealed an extensive amount of cryptic diversity. Resolving the relationships between genera in the crustose lichen family Tephromelataceae has proven difficult and the taxon limits within the genus Calvitimela are only partly understood. In this study, I tested the monophyly of Calvitimela and investigated phylogenetic relationships at different taxonomic levels. To ultimately contribute towards a more natural classification of the genus, I used an integrative taxonomic approach. Freshly collected material from Norway and fungarium specimens of all species currently assigned to Calvitimela (including available holotype, isotype and lectotype material) formed the foundations for the study. Additional population sampling of Calvitimela melaleuca sensu lato across Norway was performed. Chemical and morphological characters were analyzed to test their diagnostic values in the genus. More than 300 sequences from five different loci (ITS, LSU, MCM7, mtSSU, TEF1-α) were produced and used, together with existing molecular data, to infer phylogenetic relationships in Calvitimela. The divergence time estimates from molecular dating were used as an assisting tool to circumscribe natural taxa. Additionally, the potential reasons for non-phylogenetic signal were explored. My molecular phylogenetic results show deeply divergent lineages in Calvitimela. Morphological characters are uncovered as overlapping between divergent subgenera in the genus, whereas chemical characters are informative at the level of subgenera, but largely homoplastic at species level. Moreover, the subgenus Calvitimela is found to constitute four distinct genetic lineages, and detailed morphological examinations of C. melaleuca s. lat. reveal differences between taxa previously assumed to be morphologically cryptic. Population level analyses of C. melaleuca s. lat. corroborate the species to be paraphyletic. Furthermore, young evolutionary ages and signs of gene tree discordance indicate a recent divergence and possibly incomplete lineage sorting in the subgenus Calvitimela. Phylogenetic analysis of the mtSSU suggests that the Antarctic species C. uniseptata belongs in Lecania (Ramalinaceae). I also find molecular evidence for C. septentrionalis being sister to C. cuprea. In the subgenus Severidea, one new grouping is recovered as a highly supported sister to C. aglaea. Lastly, two fertile specimens are found to be phylogenetically nested within the sorediate species C. cuprea. I discuss the need for an updated classification of Calvitimela and the role of cryptic diversity in an evolutionary context. Through generic circumscription and species delimitation I argue for a practical taxonomy in Calvitimela. | eng |