## Simulation models

This stochastic model demonstrates the chance fluctuations in allele frequencies. Such fluctuations occur particularly in small populations as a result of random sampling among gametes.

Like in the Selection model you can change (1) Initial frequency of A (p) and (2) The number of generations, but you can also define (3) the number of individuals in the studied populations.

The program will simulate the fate of 100 populations (unless you stop the simulation by clicking the Stop simulation button) by starting from the give Initial p value. The allele frequency of each simulated population the distribution of final frequencies in subpopulations. will be shown. The program also calculates F-statistics for the final result.

You can also study the joint effects of selection and drift by varying the fitnesses of different genotypes.

2.  Selection

Natural selection is the driving force of evolution. By this simple one locus model you can study how selection changes the allele frequencies. This model is deterministic, it doesn't take into account the effect of genetic drift.

In the selection model of PopGen you can vary the fitnesses of different genotypes, and also the number of generations simulation up to 100. In the Selection model of PopGen the population size is indefinite.

The program will show graphically the allele frequency of A1. The final frequency of the latest simulation is also shown.

3.  Migration

Migration, which refers to the movement of the individuals between subpopulations, is the "glue" that holds subpopulations together, that sets a limit to how much genetic divergence can occur. If the subpopulations are finite in size, then genetic drift may result in random differences among them even with migration.

Stepping Stone Model

If migration is restricted to adjacent populations, then movement forms a stepping stone pattern. The stepping stone model can be one or two dimensional. The current simulation model is one dimensional:

In the Migration: stepping stone model of PopGen you can change:

(1) Population size of an island (N)
(2) initial frequency of A1 (p)
(3) Migration rate (m)

The PopGen model demonstrates graphically fluctuations in allele frequencies in the subpopulations.

The model also shows the change in total heterozygosity due to population subdivision. The program calculates and draws the expected heterozygosity (2pq = 1 p² q²) and the expected minus observed heterozygosity during one hundred generations The program also shows the mean p of all populations.