Phylogenetic relationships among species of Williopsis and Saturnospora gen. nov. as determined from partial rRNA sequences.

Phylogenetic relationships among those yeast species that form saturn-shaped ascospores and which are assigned to the genera Williopsis and Pichia were estimated from their extent of nucleotide sequence divergence in three regions of ribosomal RNA. The Pichia species (P. dispora, P. saitoi, P. zaruensis and P. sp. nov.) are a closely clustered group only distantly related to Williopsis, and it is proposed that they be reassigned to Saturnospora gen. nov. The extent of divergence among Williopsis species (W. californica, W. mucosa, W. pratensis, W. saturnus and W. sp. nov.) is greater than that previously observed within other ascomycetous yeast genera.