The model of selection studied in this section is similar to a model of migration. Suppose two nearby islands have populations of butterflies, with xt on the first island and yt on the second. Each...

The model of selection studied in this section is similar to a model of migration. Suppose two nearby islands have populations of butterflies, with xt on the first island and yt on the second. Each year, 20% of the butterflies from the first island fly to the second and 30% of the butterflies from the second fly to the first. Suppose there are no births and deaths.