Migration(=gene flow): movement of genes beween populations.

migration rate: the proportion of immigrants in a population AFTER migration.

Fact: migration tends to eliminate existing genetic differences between populations.

Fact: allele frequencies change in the direction of the donor/source population due to migration.

How to calculate allele frequency changes due to migration?

p(after migration) = p(of immigrants) M + p(of residents) (1-M), where M is the migration rate.