What are the three pressures that lead to biodiversity according to E. O. Wilson's theory of island biogeography?

According to E. O. Wilson's theory of island biogeography, the three pressures that lead to biodiversity are the following:

1. immigration - when species immigrate into a new area, they are mixed with the species found there and thus create a diverse biome

2. emigration - the same thing as with immigration

3. extinction events - some species become extinct and give way to another species's birth