(Biyoloji) Allopatric speciation, also known as geographic speciation, is the phenomenon where huge biological populations are physically isolated by an extrinsic barrier and evolve intrinsic (genetic) reproductive isolation, such that if the barrier breaks down, individuals of the populations can no longer interbreed. Evolutionary biologists agree that allopatry is a common way that new species arise. By contrast, the frequency of other types of speciation, such as sympatric speciation, parapatric speciation, and heteropatric speciation), is debated