What phenomenon is described by hitchhiking in genetic terms?

Hitchhiking in genetic terms refers to the increase of an allele in a population due to the selection pressure acting on a nearby linked allele. When a beneficial allele is selected for, the alleles that are physically close to it on the chromosome can also increase in frequency even if they are not directly beneficial themselves. This phenomenon occurs because of the physical proximity of genes on chromosomes; when selection favors one allele, it can inadvertently boost the frequency of adjacent alleles through its propagation in the gene pool. This effect often leads to a reduction in genetic variation near the beneficial allele, as linked alleles are swept along with it during a selective sweep, which is a core concept in understanding how genetic variation and selection interact in populations.