Two Closely Related Populations of Mice Have Been Separated for Many

question 32

Multiple Choice

Two closely related populations of mice have been separated for many generations by a river. Climatic change causes the river to dry up, thereby bringing the mice populations back into contact in a zone of overlap. Which of the following is not a possible outcome when they meet?

• A) They interbreed freely and produce fertile hybrid offspring.
• B) They no longer attempt to interbreed.
• C) They interbreed in the region of overlap, producing an inferior hybrid. Subsequent interbreeding between inferior hybrids produces progressively superior hybrids over several generations.
• D) They remain separate in the extremes of their ranges but develop a persistent hybrid zone in the area of overlap.
• E) They interbreed in the region of overlap, but produce sterile offspring.