Saccharomyces paradoxus and Saccharomyces cerevisiae are associated with exudates of North American oaks.

Genetic hybridization and karyotypic analyses revealed the biological species Saccharomyces paradoxus and Saccharomyces cerevisiae in exudates from North American oaks for the first time. In addition, two strains collected from elm flux and from Drosophila by Phaff in 1961 and 1952 were reidentified as S. paradoxus. Each strain studied showed a unique profile of chromosomal hybridization with a probe for the retrotransposable element Ty1. The wild distribution of natural Saccharomyces sensu stricto yeasts is discussed.