Identifying Allopatric Speciation

In the study of evolution, particularly in relation to speciation, biologists recognize several different mechanisms through which species can diverge from a common ancestor. One such mechanism is called allopatric speciation, which occurs when a population is geographically separated. Over time, genetic drift, natural selection, and mutation can lead to the emergence of distinct species. In contrast, sympatric speciation occurs without geographical separation, often through mechanisms like polyploidy or behavioral isolation. The adaptability of species to their environments is also influenced by the availability of resources, environmental pressures, and reproductive strategies.

Given this context, consider the following scenario: Two populations of a species of lizard were separated by a mountain range which formed due to tectonic activity. The lizards on either side of the mountain range began to adapt to different environments, leading to their eventual divergence into two distinct species. This situation exemplifies which of the following concepts of evolution?