Different species are defined as groups that do not exchange genes.
Even when viable hybrids can form, gene flow between species may nevertheless be prevented if genes from different species are incompatible, preventing hybrids from reproducing. The Leverhulme Trust has funded a project led by Duncan Greig (research profile
) to identify such "speciation genes" causing sexual sterility in yeast hybrids. The project will use genetic manipulation to generate recombinant hybrid genomes with compatible and incompatible combinations of two species genes. Sequencing many recombinant hybrid genomes will reveal the locations and identities of yeast speciation genes.