Plate tectonics can have a big effect on evolutionary change. For example, about 30 million years ago, South America and Antarctica were the same landmass. A continental shift ripped Antarctica from the tip of South America, changing the water currents. The previously warm water slowly became colder, and fish were forced to migrate. Some of them moved south, others north. As the seas got colder, most of the fish died out. One species fish mutated antifreeze in it's blood, so it could survive. Soon this species was the only one left, and it branched into sub-species, populating Antarctica's seas.
One of the many species of Notothenioid fish: