What is a primary consequence of geographical isolation?

Geographical isolation is a significant factor in the process of speciation, which occurs when populations of a species become separated by physical barriers, such as mountains, rivers, or distance. This separation prevents gene flow between the isolated populations, meaning there is reduced or no interbreeding. Over time, these populations experience different environmental pressures, leading to natural selection acting on them independently. As a result, genetic mutations can accumulate in each population, leading to increased divergence.

This divergence often results in populations adapting to their unique environments, thus becoming sufficiently different from one another in terms of genetic, phenotypic, and behavioral traits. These changes may ultimately result in the formation of new species, as the populations can end up having different reproductive strategies or mechanisms that prevent them from mating successfully even if they come into contact again.

The other options do not accurately reflect the outcome of geographical isolation. For example, increased genetic similarity within a population contradicts the process of evolution through divergence, and interbreeding typically ceases as the populations become more isolated. Physical barriers are indeed created as a result of geographical isolation rather than being prevented.