Allopatric species inhabit different geographical areas. The allopatric speciation arises as a result of two populations of the same species becoming isolated from each other due to geographical barriers. It is a very slow and gradual process due to which one species evolve into two different species. The geographical barrier may be due to the formation of a new mountain range or river or canyons that hinders the physical interaction between two populations of the same species.
All others are occupying same geographical area but are reproductively isolated. Sympatric species occupy the same geographical area and speciation arises due to mutation or polyploidy. Biospecies are sexually interbreeding individuals that are isolated reproductively from other species. Sibling species are morphologically similar but reproductively isolated species.