What characterizes allopatric speciation?

Allopatric speciation is characterized by reproductive isolation that arises when populations of a species become geographically separated, preventing them from interbreeding. This geographical barrier might include physical features such as mountains, rivers, or distances that isolate populations on different islands or regions. Over time, these separated populations can experience different environmental pressures and evolutionary paths, leading to the divergence of species.

The correct answer reflects the essence of allopatric speciation, where the physical separation is crucial for the development of distinct species through evolutionary mechanisms like natural selection, genetic drift, and mutation that act on each isolated group independently. This process can ultimately lead to the accumulation of significant genetic differences, resulting in the emergence of new species.

In contrast, the other options describe mechanisms or situations that do not align with the primary definition of allopatric speciation. For example, occurring within the same geographical area pertains to sympatric speciation, while behavioral isolation pertains to factors affecting mating choices but not necessarily linked to physical separation. Polyploidy, often observed in plants, is a different mechanism of speciation that typically does not involve geographical isolation.