Both heterothallic and homothallic strains of Dictostelium can undergo mating. The first is outcrossing (in heterothallic fungi). "P. capsici" is a heterothallic oomycete. Thus the capability for heterothallic sex is maintained even though little genetic diversity is produced. "Aspergillus fumigatus", is a heterothallic fungus. Heterothallic species have sexes that reside in different individuals. These fungi are said to be homothallic, versus the normal heterothallic species with mating types. The production of a zygote requires two cells of different mating types (heterothallic). In heterothallic fungi, two different individuals contribute nuclei to form a zygote. Heterothallic strains of different mating type can conjugate to form zygospores. Heterothallic species have mating strains, designated as A1 and A2. Homothallic species may likely have evolved from heterothallic ancestors (Lin and Heitman 2007). The yeast "Saccharomyces cerevisiae" is heterothallic. The heterothallic strains have two mating types, mt(-) and mt(+). Heterothallic species perform anastomosis when haploid monokaryon come in contact with one another.