Population structure - Wahlund’s effect

 

• Wahlund’s effect: As long as allele frequencies vary among subpopulations, even if each subpopulation exhibits HW proportions, then more homozygotes will be observed than would be expected based on the allele frequency of the metapopulation 

• The relative increase in homozygosity is proportional to the variance in allele frequencies among subpopulations, as measured by F (where 0 ≤ F ≤ 1) 

• F is commonly known as Wright’s fixation index and may be most simply interpreted as F = 1 – (Hobs / Hexp ), where the values represent observed and expected levels of heterozygosity