Population Subdivision

population subdivision entails an inbreeding like effect

decrease in the proportion of heterozygous genotypes

a sub-structured population has 3 levels of complexity

• individual organisms (I)

• subpopulations (S)

• total population (T)

H_I

the heterozygosity of an individual in a population

H_s

the expected heterozygosity of an individual in an equivalent random mating subpopulation

H_T

the expected heterozygosity of an individual in an equivalent random mating total population

H_I can be interpreted as

the average actual observed heterozygosity of all the genes/loci in an individual, or as the probability of heterozygosity of an one gene/locus

H_s represents the

level of heterozygosity that would be found in a subpopulation if the subpopulation were undergoing random mating, therefore H_s always equals 2p_iq_i for a subpopulation with allele frequency p_i

H_s always equals

2p_iq_i for a subpopulation with allele frequency p_i

H_T represents what the

heterozygosity would be, were all sub populations pooled together and mated randomly, if the average allele frequency among subpopulations is p₀ then H_T equals 2p₀q₀

if the average allele frequency among subpopulations is p₀ then

H_T equals 2p₀q₀

what is the inbreeding coefficient

F_IS

the inbreeding coefficient F_IS measures

the reduction in heterozygosity of an individual due to random mating within its subpopulation

what is the equation for measuring heterozygosity of an individual due to nonrandom mating within its subpopulation

what is the equation for the reduction in heterozygosity of a subpopulation due to genetic drift

what is the equation for the reduction in heterozygosity of an individual relative to the total population

F_IS is concerned with

inbreeding within individuals

F_ST is concerned with

inbreeding in subpopulations

F_IT is concerned with

inbreeding in individuals relative to the total population

what is the most inclusive measure of inbreeding that takes into account both effects of nonrandom mating and effects of population subdivision

F_IT

what is the mathematical relationship between F_IS/F_ST/F_IT

F_IS in natural populations is

typically close to 0

when F_IS=0 then

F_ST=F_IT

the fixation index F_ST is a good estimate of

total inbreeding coefficient

F_ST is used as a measure of

genetic difference among populations

F_ST is influenced by

• random genetic drift

• migration

• natural selection

• mutation

F_ST minimum = 0 then

no genetic divergence

F_ST maximum = 1.0 then

fixation for alternative alleles in subpopulations

F_ST = 0-0.05 then

little genetic differentiation

F_ST = 0.05-0.15 then

moderate genetic differentiation

F_ST = 0.15-0.25 then

great genetic differentiation

F_ST = >0.25 then

very great genetic differentiation

as random drift occurs from generation to generation

the value of F will change (increase)