Lichens in the genus Platismatia are common, widespread and were some of the first to be studied by Western taxonomists. However, few molecular phylogenetic studies of Platismatia have been published to date. We present an expanded phylogeny of Platismatia inferred from 60 newly generated ITS sequences and 28 existing publicly available sequences. The new phylogeny confirms the delimitation of P. wheeleri as monophyletic and distinct from the widespread P. glauca, the latter of which was recovered as two separate, highly supported clades, that do not appear to differ in phenotype or biogeography. The western North American endemics P. herrei and P. stenophylla were not recovered as reciprocally monophyletic and may be an example of recent speciation similar to that also hypothesized for Alectoria in the same region. Ancestral state reconstructions of reproductive modes (dominant asexual vs. sexual reproduction; asexual propagule type) suggest that sexual species like P. tuckermanii can evolve from primarily asexual ancestors. Evaluation of species distributions suggests that reproductive mode may be related to range size. These data suggest that Platismatia could serve as a model for future studies on reproductive mode, biogeography and speciation in lichens.