Allopatric speciation due to geographic separation of the Grand Canyon.
Harris's antelope squirrel (Ammospermophilus harrisi) inhabits the canyon's south rim (left).
Just a few miles away on the north rim (right) lives the closely related white-tailed antelope squirrel
(Ammospermophilus leucurus).
Another example is the Tassel-eared Squirrel, where Abert's Squirrel (Sciurus aberti) lives on the south rim and the
Kaibab Squirrel (Sciurus aberti kaibabensis) lives on the north rim.