Which would be a consequence of high levels of gene flow among neighboring populations?

• A. Increased genetic differentiation
• B. Greater genetic similarity between populations due to shared alleles
• C. Increased genetic diversity within populations but greater differences between populations
• D. Genetic variation within populations decreases while differences between populations increase

Answer: (C)

High levels of gene flow move alleles between neighboring populations, so allele frequencies begin to converge and the populations share more of the same genetic variants. This exchange makes them genetically more alike, reducing differences between populations. At the same time, bringing in new alleles can increase genetic variation within a population, but the hallmark effect is the smoothing out of differences among populations due to shared alleles. So the situation described by saying populations become more similar because they share alleles best captures the outcome of high gene flow. The idea that diversity within a population increases while differences between populations rise would not fit the typical outcome of substantial gene flow.