Model 1 - Allopatric Speciation Geographic isolation is an isolating mechanism in nature. Over long periods of time, it can lead to speciation. As the name suggests, geographic isolation is when populations of a species become separated geographically. This could also happen from the founder effect, where a small group breaks away from a larger population and establishes a group in an isolated area. Isolation could also occur when a geographic event, like an earthquake or a landslide separates a population.

Once the populations are separated evolution can occur through multiple mechanisms. Natural selection could act on each population, where some individuals have favorable traits for survival. Genetic drift can occur, where genotypes become more common due to random chance. These mechanisms can lead to each subpopulation becoming so different, that they can no longer interbreed and are considered separate species.