The mating of compatible hyphae is genetically determined. Most of the gourmet species are governed by two incompatibility factors (A and B). As a result only subsets of spores are able to combine with one another. When spores germinate, several strains are produced. Incompatible strains grow away from each other, establishing their own territorial domains. In this sense, spores from one mushroom can actually compete with one another for the same ecological niche.