Why is linkage disequilibrium important in evolutionary biology?

Linkage disequilibrium refers to the non-random association of alleles at different loci in a population. Its significance in evolutionary biology is particularly clear when considering its role in the effectiveness of natural selection on linked alleles. When genes are close together on a chromosome, they are more likely to be inherited together, which can influence how natural selection acts on those genes.

If a beneficial allele is in linkage disequilibrium with a deleterious allele, the deleterious allele may also be passed on at a higher frequency than it would be if alleles were assorting independently. This can hinder the effectiveness of natural selection since the advantageous effects of one allele can be masked by the presence of a linked less advantageous allele. Conversely, if beneficial alleles are linked, they may experience a higher rate of fixation within the population than if they were independently assorted.

The understanding of linkage disequilibrium is crucial for mapping genetic traits and understanding how evolutionary processes shape the genetic structure of populations over time. This makes it a fundamental concept for understanding the dynamics of evolution.