Amanita ovoidea is generally considered edible and is morphologically similar to Amanita proxima that contains nephrotoxins. Both species were assigned to Amanita section Amidella. To study their phylogenetic relationships, we performed nrITS- and RPB2-based analyses of these and other Amanita species. Our analyses show that (i) A. ovoidea and A. proxima are distinct species; (ii) A. ovoidea has an extensively heterogeneous ITS with up to 4.4% pairwise genetic distance between individuals; (iii) in A. ovoidea, pairwise genetic distance between ITS clones from a single basidiome was as high as 3.2%, possibly because ofhybridization events and subsequent failure of the rDNA repeats to homogenize; (iv) A. aminoaliphatica and A. proxima are taxonomic synonyms; and (v) A. proxima and A. ovoidea cluster with species belonging to section Roanokenses rather than with those of section Amidella sensu stricto. This study supports the development of species-specific markers for diagnosis of the toxic and the edible species here examined
