Once members of a species are geographically isolated, what factors may cause them to differ from each other over time

When members of the same species are geographically isolated over time they will start to differ because of multiple factors:
1. Climate
2. Relief
3. Vegetation
4. Competition
5. Size of the area (specifically referring to smaller islands)
All of this factors (if different) will require a change in the behavior of the species, change in color, change in size, adaptation towards the food source by changing the teeth/beak and thus the jaw structure (for the species that have them), develop a new strategy to hunt (if it's a hunter), or develop a new strategy for evading predators, maybe change the niche in the food chain if there's stronger competition.