Allopatric speciation primarily occurs due to which of the following?

Allopatric speciation primarily occurs due to geographical division, which leads to the physical separation of populations. When a population is split by a geographic barrier, such as mountains, rivers, or distances, the isolated groups can no longer interbreed. This separation allows for independent evolutionary trajectories, during which genetic divergence can occur due to natural selection, mutation, and genetic drift.

Over time, these isolated populations can accumulate enough genetic differences that, even if they come into contact again, they are no longer able to interbreed successfully, resulting in the formation of two distinct species. This process is a fundamental mechanism of speciation in which geographical factors play a crucial role, supporting the idea that physical separation is a key driver of allopatric speciation.