Internal Transcribed Spacer Sequences from 38 Recognized Species of Suillus sensu lato: Phylogenetic and Taxonomic Implications

Internal transcribed spacer regions of the nuclear ribosomal repeat have been sequenced from 47 isolates belonging to 38 recognized species of Suillus sensu lato. The sequences have been analyzed for phylogenetic and taxonomic implications using parsimony as well as distance methods. Based on these data, the genera Boletinus and Fuscoboletinus, that are often recognized within Suillus sensu lato, are not monophyletic. Isolates of Suillus granulatus derived from either North America or Europe and Asia are polyphyletic and seem to represent at least two different species. Our data also suggest that within Suillus sensu lato, mycorrhizal associations with Larix are primitive and host changes to Pinus and Pseudotsuga seem to have occurred only once. Changes among host species of the same genus appear to be more frequent. Finally, the most primitive clade within Suillus sensu lato seems to be formed by organisms with a strongly boletinoid hymenophore.