Suppose there are 100 butterflies on each island at time t = 0. How many are on each island at t = 1? At t = 2?
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.