Calculate F-statistics (Fst, Fis, Fit) to measure population differentiation and inbreeding coefficients from genotype data.
Fst (Population Differentiation)
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Fis (Inbreeding Coefficient)
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Fit (Overall Fixation Index)
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Total Individuals
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Fst measures population differentiation (genetic distance between populations), Fis measures inbreeding within populations (deviation from Hardy-Weinberg equilibrium), and Fit measures overall fixation index (combined effect of population structure and inbreeding).
F-statistics range from -1 to +1. Positive values indicate reduction in heterozygosity (inbreeding or population structure), zero indicates random mating, and negative values indicate excess heterozygosity (heterozygote advantage or population mixing).
A high Fst value (approaching 1) indicates strong population differentiation, meaning the populations are genetically distinct. Low Fst values (near 0) suggest little genetic difference between populations.
Allele frequency is calculated as: frequency of A = (2 × AA + Aa) / (2 × total individuals). Each homozygote contributes two alleles, each heterozygote contributes one allele of each type.
The three F-statistics are related by the equation: (1 - Fit) = (1 - Fis)(1 - Fst). This shows how overall fixation index combines the effects of inbreeding and population structure.
F-statistics are useful for analyzing population structure, measuring genetic diversity, detecting inbreeding, studying gene flow between populations, and understanding evolutionary processes in natural and managed populations.
Larger sample sizes provide more reliable estimates. Generally, at least 25-50 individuals per population are recommended, though this depends on the allele frequencies and the precision required for your study.