16. Which of the following is not an example of allopatric speciation?
A) The Isthmus of Panama arose 10 million years ago dividing a species of snapping shrimp into two separate populations. Over time, individuals on one side of the isthmus became reproductively isolated from individuals on the other side.
B) A species of hummingbird lives on mainland Costa Rica. Ten individuals make their way to a small island off the coast. Over time these island birds become reproductively isolated from the mainland birds.
C) A squirrel population was divided into two groups because of the formation of the Grand Canyon. Since that time, genetic changes have occurred and the two groups of squirrels are now reproductively isolated from one another.
D) Two populations of deer are separated by a river. Over millions of years, the river dries up. When the two deer populations meet, they are able to interbreed successfully.
E) All of these are examples of allopatric speciation.
Why is D considered allopatric speciation? I thought that D is the correct answer because if the two deer populations are able to interbreed, then speciation did not occur; so it cannot be considered allopatric speciation. â