Interact box Finite island model of gene flow

Use PopGene.S2 to simulate the island model of gene flow among a large (but finite) number of demes. Launch the program, click on the Gene Flow and Subdivision menu, and select the F-Statistics module. Run simulations with the following values for the effective population size, the migration rate, and the initial allele frequency.

Ne m Initial allele frequency p

For each simulation run, examine the allele frequencies over time and record the different hierarchical heterozygosity measures (H,, HS, and HT) and fixation indices (FIS, FST, and FIT).

What is happening when the allele frequency lines sometimes hit the top or bottom axis (go to fixation or loss) and then reappear? What are the units of the migration values you entered in the model parameters box? Why does increasing m maintain lower FSTand FITvalues? How does migration counteract genetic drift? Is migration always able to do this?

Table 4.9 Estimates of the fixation index among subpopulations (JST) for diverse species based on molecular

genetic marker data for nuclear loci. Different estimators were em

ployed depending on the type of

genetic marker and study design. Each FST was used to determine the effective number of migrants (Nm)

that would produce an identical level of population structure under the assu

mptions of the infinite island

model according to equation 4.63.

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