6.2 Population structure

Population structure is a consequence of the fact that when two groups of individuals do not freely interbreed, the two populations typically develop different patterns of genetic variation.

Individuals within a population tend to be share greater genetic similarity with each other than with individuals in other populations. These differences manifest through differences in allele frequencies among populations, and result from genetic drift, natural selection, and other evolutionary forces.

We can measure such allele frequency differences to reveal evolutionary relationships among populations, as well as evidence of historical natural selection.

Fig. 1. Two populations polymorphic for alleles A and a. The frequency of A in Population 1 is 0.83, while its frequency in Population 2 is 0.15.
Fig. 1. Two populations polymorphic for alleles A and a. The frequency of A in Population 1 is \(0.83\), while its frequency in Population 2 is \(0.15\).
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