Geographic isolation causes speciation because members of a population are unable to reproduce with one another. This reproductive isolation prevents mixing of the gene pool and allows each population to evolve along different paths according to the specific pressures present in the differing environments.
Members of a population may become geographically isolated due to changing climate or terrain. Once isolated from the main group, a population begins to adapt to the specific environment in which it is located. If the environments are diverse, a population that is geographically isolated from other members of the population may diverge into a separate species over time.
Populations do not have to be geographically isolated to prevent mixing of the gene pool. Some populations are isolated from the main group because they live in a different portion of the ecosystem. This type of isolation is called ecological isolation.
Members of a population may have different mating rituals or breeding times that result in loss of the opportunity to breed. Isolation due to different breeding patterns is called temporal isolation. Behavioral isolation occurs when differing mating rituals cause speciation. Sometimes speciation occurs due to the physical inability of members of a population to breed with one another. This process is known as mechanical isolation.