1. adaptive radiation in island chains (finches; honeycreepers)
2. exploiting a new niche in a common location
3. extrinsic factor prevents two or more groups from mating with
each other regularly
4. gene flow has been reduced between flies that feed on
different food varieties, even though they both live in the same
geographic area.
5. genetic polymorphism results in reproductive isolation
6. population isolated from another due to geographic barrier
7. populations remain in same physical area.
8. the gradual formation of the grand canyon split a population
into 2 divergent species.