Background selection

Background selection is the loss of genetic diversity at a location in the genome caused by negative selection against nearby harmful mutations with which it is closely linked on the chromosome. A genetic variant can be eliminated from a population not because it is itself harmful, but because it sits next to a mutation that is. This shows that the genetic background surrounding a mutation can shape whether that mutation persists in a population, which runs against the simpler assumption that individual genetic sites evolve independently of their neighbors.