Biology of the ectomycorrhizal genus Rhizopogon.: V.: Phylogenetic relationships in the Boletales inferred from LSU rDNA sequences

The phylogenetic relationship between Alpova, Chroogomphus, Gomphidius, Rhizopogon, Suillus, and Truncocolumella and their placement in the Boletales was tested through maximum parsimony analyses of large subunit nuclear ribosomal DNA sequences. Taxon sampling included representatives of the genera Alpova, Boletellus, Boletus, Chroogomphus, Gomphidius, Melanogaster, Paragyrodon, Phylloporus, Rhizopogon, Suillus, Truncocolumella, Tylopilus, and Xerocomus, as well as species from the Agaricales, Russulales, and Polyporales. The order Boletales was strongly supported as monophyletic. Furthermore, within this order, two major groups emerged: the boletoid radiation and a Melanogastraceae/Paragyrodon sphaerosporus paraphyletic assemblage, and the suilloid radiation. The boletoid radiation and a Melanogastraceae/Paragyrodon sphaerosporus assemblage was strongly supported. Although the boletoid radiation was not strongly supported by bootstrap analysis, the clade did not collapse in the strict consensus topology. This clade comprised species from the genera Boletellus, Boletus, Phylloporus, Tylopilus, and Xerocomus. The Boletaceae sensu Singer was not monophyletic. Although species relationships within the boletoid radiation were not well resolved, the genus Boletus did not appear to be monophyletic. Alpova diplophloeus, A. trappei, Melanogaster tuberiformis, and Paragyrodon sphaerosporus formed a paraphyletic assemblage basal to the boletoid radiation clade. The suilloid clade was strongly supported and included Alpova olivaceotinctus, Chroogomphus, Gomphidius, Rhizopogon, Suillus and Truncocolumella citrina. Species in the genus Alpova therefore were grouped both within and outside the suilloid radiation. Within the suilloid radiation, Suillus was inferred to be more closely related to Truncocolumella citrina and the Gomphidiaceae than to Rhizopogon, suggesting a more distant relationship between Suillus and Rhizopogon than previously hypothesized. Rhizopogon was not supported as monophyletic, although its monophyly could not be rejected by the data. Alpova olivaceotinctus grouped within the genus Rhizopogon, consistent with previous classifications, and is returned to that genus.