Phylogeny of Calostoma, the gelatinous-stalked puffball, based on nuclear and mitochondrial ribosomal DNA sequences

Nucleotide sequence of the nuclear small and large subunit and the mitochon drial small and large ribosomal genes of Calostoma were used to investigate evolutionary relationships with Other Basidiomycetes. In separate analyses with each gene, Calostoma was placed within the Boletales and outside the clades containing most gilled mushrooms, puffballs, stalked puffballs, eart hstars, stinkhorns and nonboletalean Gasteromycetes. This contradicted prev ious taxonomic hypotheses. Calostoma was most closely related to Gyroporus, Pisolithus, and Scleroderma based on maximum parsimony and maximum likelih ood analysis of the mitochondrial large ribosomal gene database, which cont ained several representatives of most genera of the Boletales. In three of the four gene trees Calostoma shows an unusually high number of inferred nu cleotide substitutions relative to other Boletales; this corresponds to its extreme morphological divergence.