What type of speciation is repressed by the Grand Canyon squirrels?
The Grand Canyon squirrels, specifically the Kaibab squirrel (Sciurus aberti kaibabensis) found on the North Rim, and the Abert's squirrel (Sciurus aberti) found on the South Rim, provide a classic example of allopatric speciation.
Allopatric speciation occurs when a geographic barrier, such as the Grand Canyon, separates members of a species into two groups. Over time, because the two populations are isolated from one another, genetic differences accumulate due to factors such as mutation, genetic drift, and natural selection in their respective environments. This can eventually lead to the formation of two distinct species that are no longer able to interbreed.
The Grand Canyon acts as a significant physical barrier preventing gene flow between the squirrel populations on the North and South Rims. As a result, the two squirrel types have developed distinct morphological and genetic differences. Although they were once the same species, the division 'created' by the canyon's formation has led to the divergence of the Kaibab squirrel and the Abert's squirrel.