Phylogenetic analysis of restriction site data. Statistical Genomics , Chapter 3. Restriction sites can be assayed for polymorphism within a population by Southern hybridization.
Restriction sites can reveal polymorphism between genotypes.
DNA sequences are mutating all the time. As two populations diverge over time, they each accumulate different mutations at different sites. When restriction sites in the vicinity of a given gene are compared from one genotype to another, one genotype may have the site, and the other will not. This is referred to as a polymorphism . High polymorphism between two genotypes is evidence of genetic divergence.