Since the Pleistocene Ice Age, Deserts Have Been Gradually Forming

Multiple Choice

Since the Pleistocene ice age, deserts have been gradually forming in the southwestern United States. As the original lakes and rivers of this area shrank into isolated streams, ponds, and springs, the fishes living in them developed a strong potential for:

A) speciation.
B) hybridization.
C) mechanical incompatibility.
D) temporal isolation.
E) hybrid inviability.