Sexual agglutination of heterothallic yeasts in diverse taxonomic areas.

Species in four genera of yeasts produce mating types that clump when brought together in liquid or on solid media. All species of a phylogenetic line of Saccharomyces are sexually agglutinative. Unisexuals of the latter species are believed to have from one to four sets of chromosomes, whereas bisexuals are believed to have from two to eight sets.