Question

Drosophila mojavensis and Drosophila arizonae are closely related and reproductive isolation between them is incomplete. They have overlapping distributions in the Sonoran Desert, although there are also areas where they occur allopatrically. Which of the following conditions would be required in order to infer reinforcement?

1) premating isolation is stronger in areas where they are allopatric than in areas where they are sympatric
2) there is postzygotic isolation in areas where they are sympatric
3) premating isolation is stronger in areas where they are sympatric than in areas where they are allopatric
4) b and c are both required
5) a and b are both required

Answer 1

In order to infer reinforcement between Drosophila mojavensis and Drosophila arizonae, both stronger prezygotic isolation in sympatric areas and the presence of postzygotic isolation are required.

Step-by-step explanation:

Reinforcement occurs when there is a strengthening of prezygotic isolation between closely related species in areas where they are sympatric compared to areas where they are allopatric. This means that the barriers to reproduction before the formation of a zygote are stronger in sympatric areas. Additionally, the presence of postzygotic isolation in areas where the species are sympatric can also support the inference of reinforcement. Therefore, the conditions required to infer reinforcement would be option 5) a and b are both required.