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 Canyonwas 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
stabilizing selection.
speciation.
:: genetic equilibrium.
:: selection on single-gene traits.