What does partial reproductive isolation imply in stickleback populations?

What does partial reproductive isolation imply in stickleback populations?

• A. Complete lack of interbreeding between populations.
• B. Some gene flow but reduced or nonzero interbreeding between populations.
• C. No reproductive differences between populations.
• D. Random mating across populations.

Answer: (B)

Partial reproductive isolation means there are barriers that reduce interbreeding between populations, but they don’t stop it completely. In sticklebacks, this leads to some gene flow because individuals can still mate across populations, though less frequently or with fewer successful offspring. So you have reduced but nonzero interbreeding between populations. The idea rules out complete lack of interbreeding (that would be full reproductive isolation), and it also rules out no reproductive differences or random mating across populations, which would indicate little to no isolation.

Partial reproductive isolation means there are barriers that reduce interbreeding between populations, but they don’t stop it completely. In sticklebacks, this leads to some gene flow because individuals can still mate across populations, though less frequently or with fewer successful offspring. So you have reduced but nonzero interbreeding between populations. The idea rules out complete lack of interbreeding (that would be full reproductive isolation), and it also rules out no reproductive differences or random mating across populations, which would indicate little to no isolation.