Retiboletus, a new genus for a species-complex in the Boletaceae producing retipolides1

Boletus ornatipes and B. retipes are two closely related species in North America, which cannot be differentiated by morphological and anatomical characters. The 25S rDNA was partly sequenced from several isolates of B. ornatipes, B. retipes, and allied species in the Boletaceae to aid identification. The phylogenetic analysis using maximum likelihood suggests that both species are differently distributed. In addition, our results are supported by a previous study of HELLWIG (1999), separating three groups in the B. retipes/ornatipes-complex based on chemotaxonomical characters. Retipolides form the major pigments in presently analyzed B. ornatipes and B. retipes collections and are also detected in B. flavoniger. This group of secondary metabolites is unique in the Boletales (for distribution of pigments in Boletales see GILL & STEGLICH 1987) and is characteristic of the new genus Retiboletus, in which B. ornatipes (type), B. retipes, and B. flavoniger are placed. A positive proof of retipolides is still missing in B. griseus and Tylopilus nigerrimus. Both species are transferred to Retiboletus according to morphological characters and sequence data.