AbstractBackgroundIn this study, we investigate species limits in the cyanobacterial lichen genusRostania(Collemataceae, Peltigerales, Lecanoromycetes). Four molecular markers (mtSSU rDNA, β-tubulin, MCM7, RPB2) were sequenced and analysed with two coalescent-based species delimitation methods: the Generalized Mixed Yule Coalescent model (GMYC) and a Bayesian species delimitation method (BPP) using a multispecies coalescence model (MSC), the latter with or without an a priori defined guide tree.ResultsSpecies delimitation analyses indicate the presence of eight strongly supported candidate species. Conclusive correlation between morphological/ecological characters and genetic delimitation could be found for six of these. Of the two additional candidate species, one is represented by a single sterile specimen and the other currently lacks morphological or ecological supporting evidence.ConclusionsWe conclude thatRostaniaincludes a minimum of six species:R. ceranisca,R. multipunctata,R. occultata1,R. occultata2,R. occultata3, andR. occultata4,5,6. Three distinctNostocmorphotypes occur inRostania, and there is substantial correlation between these morphotypes andRostaniathallus morphology.