Two bird species overlap in a hybrid zone. They are isolated by a slight difference in the male songs and by the females' tendency to select males with the "correct" song. Hybrid offspring tend to have reduced fertility compared to either of the parent species. What effect might natural selection have in this situation?
A) Natural selection might favor males with less distinctive calls and/or females that are less "choosy."
B) Natural selection might favor males with more distinctive calls and/or females that are more "choosy." As a result, the reproductive barrier between the two species could be reinforced.
C) Natural selection could lead to the hybrid species taking over and eliminating the weaker parent species.
D) Natural selection could lead to the stronger of the two species taking over and eliminating the other species.

Question

Quizplus · Accepted Answer

Natural selection would favor individuals with traits that reinforce the reproductive barrier between the two species. This means that males with more distinctive calls and females that are more "choosy" and have a stronger preference for the "correct" song would be favored. This would reinforce the reproductive isolation between the two species, reducing the likelihood of hybridization and maintaining the separate genetic identities of the parent species.

Two Bird Species Overlap in a Hybrid Zone