Arizona’s Grand Canyon was formed creating a geographic barrier between the squirrels that lived there. They could no longer contact and reproduce with each other. Two separate species inhabit the north and south rims of the canyon. The Kaibab squirrels inhabit the north rim and the Abert squirrels inhabit the south rim. According to National Geographic, this type of speciation is allopatric speciation. In the article, it says, “Allopatric speciation occurs when a species separates into 2 separate groups which are isolated from one another…When Arizona’s Grand Canyon formed, squirrels and other small mammals that had once been part of a single population could no longer contact and reproduce with each other across this new geographic barrier.”
This leads me to say that according to Macroevolution, the type of reproductive barrier that is causing these 2 species to split is called Geographical Isolation. It says that, ” The Kaibab squirrel became geographically isolated from the common ancestor with its closest relative, the Abert squirrel in the North Rim of the Grand Canyon about 10,000 years ago.” This indicates that it is geographical isolation because the Grand Canyon is literally a physical barrier between the two species.
