A small group of individuals leave a larger population and colonize a new area that is physically separated from the original population. Due either to chance or genetic drift, the genetic composition of the new colony differs from the larger population. This is an example of

That would be an excellent example of allopatric facts. In addition, the allopatric speciation mainly occurs due to when different species gets separated geographically by landforms, therefore, new traits and characteristics continuously develop and therefore different subspecies began to spring.