Intercontinental distributions of species of Cortinarius, subgenus Phlegmacium, associated with Populus in western North America

Three species of Cortinarius subg. Phlegmacium, Cortinarius argutus Fr. and Cortinarius hedyaromaticus C. Cripps & O.K. Mill. (section Arguti stat. nov.) and Cortinarius talus Fr. (section Multiformes), are compared from western North America and Europe. Phylogenetic analysis of the ITS region shows that C. argutus and C. hedyaromaticus are separate, closely related species with rooting stipes. Cortinarius talus is a pale species with a bulbous stipe and a sweet odor similar to that of C. hedyaromaticus; C. argutus lacks this sweet odor. All three species have intercontinental distributions and are associated with deciduous trees, primarily Populus tremuloides Michx., Populus tremula L., but also Salix spp. This study highlights the importance of the study of type specimens and molecular analysis to stabilize the application of established names.