Which of the following is a key factor in the process of speciation?

Geographical barriers play a crucial role in the process of speciation by physically separating populations of a species. When populations are divided by a geographical barrier, such as mountains, rivers, or other significant landscape features, gene flow between these groups is reduced or eliminated. This isolation allows for evolutionary processes to take place independently in each population.

Over time, the separated populations may adapt to their unique environments, undergo different mutations, and experience divergent natural selection pressure. As these changes accumulate, the populations can evolve into distinct species, acquiring differences that can prevent them from interbreeding even if they come back into contact later.

In contrast, gene flow between populations would typically prevent speciation by introducing new genetic material and homogenizing the gene pools, while seasonal changes in an environment might influence the behavior or reproduction of organisms but do not directly lead to the formation of new species. Increased competition can lead to shifts in populations and adaptations, but it is not a direct factor in creating new species without the isolation that geographical barriers provide.