|1||Department of Botany and Plant Pathology, Oregon State University, Corvallis OR 97331-2902|
|2||Department of Forest Science, Oregon State University, Corvallis OR 97331-5752|
|3||U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station, Forestry Science Laboratory, 3200 Jefferson Way, Corvallis OR 97331|
|4||current address: University of California at Berkeley, Department of Plant and Microbial Biology, 111 Koshland Hall, Berkeley CA 94720-3102|
Rhizopogon (Basidiomycota, Boletales) is a genus of hypogeous fungi that form ectomycorrhizal associations mostly with members of the Pinaceae. This genus comprises an estimated 100 species, with the greatest diversity found in coniferous forests of the Pacific northwestern United States. Maximum parsimony analyses of 54 nuclear ribosomal DNA internal transcribed spacer (ITS) sequences including 27 Rhizopogon and 10 Suillus species were conducted to test sectional relationships in Rhizopogon and examine phylogenetic relationships with the closely related epigeous genus, Suillus. Sequences from 10 Rhizopogon type collections were included in these analyses. Rhizopogon and Suillus were both monophyletic. Rhizopogon section Rhizopogon is not monophyletic and comprised two clades, one of which consisted of two well supported lineages characterized by several long insertions. Rhizopogon sections Amylopogon and Villosuli formed well supported groups, but certain species concepts within these sections were unresolved. Four species from section Fulviglebae formed a strongly supported clade within section Villosuli. Subgeneric taxonomic revisions are presented.