Originally only one squirrel species inhabited the Ponderosa pine forest around the rim of the Grand Canyon, the Abert squirrels. About 10,000 years ago when Arizona’s Grand Canyon Was formed, the squirrels were separated into two species - the Abert squirrels, who inhabit the south rim; and the Kaibab squirrels, who inhabit the north rim. One population of squirrels had become two separate populations that could no longer reproduce. These squirrels are an excellent example of
allopatric speciation, where a single population is separated into two geographically isolated populations, leading to the evolution of distinct species. The physical barrier created by the Grand Canyon prevented gene flow between the populations, allowing for genetic divergence and ultimately the formation of two separate species. In this case, the Abert and Kaibab squirrels have adapted to their respective environments on either side of the canyon, demonstrating the power of natural selection in driving evolutionary change.
