Species delimitation in taxonomically difficult lichen-forming fungi: An example from morphologically and chemically diverse Xanthoparmelia (Parmeliaceae) in North America

► Traditional morphological characters misrepresent species diversity in Xanthoparmelia. ► Vagrancy, distinct chemistries, and reproductive modes evolved independently multiple times. ► Diversity of vagrant Xanthoparmelia has been underestimated. ► Molecular species delimitation methods here provide an alterative hypothesis for species circumscription.