Speciation is an evolutionary process that results in the divergence of biological lineages and the emergence of reproductive isolation between lineages. The Dobzhansky-Muller model explains how reproductive incompatibility can arise between two diverging sister lineages.
When one ancestral lineage splits into two (as occurs when a geographic barrier divides populations in different parts of a species range, for example), the two lineages begin to diverge genetically. A new allele may arise at one locus in one of the lineages and become fixed in the population by genetic drift or natural selection. A different allele may arise at a second locus in the other lineage and also become fixed. If these two alleles at different loci are functionally incompatible with one another, hybrid individuals would be inviable, making the two lineages reproductively isolated.
The Dobzhansky–Muller Model
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