A population of birds lives on a small island. Another population of the same species lives on the mainland. The distance between the island and the mainland is too great for birds to fly back and forth. Recently, a series of sandbars and tiny islands have formed between the island and the mainland. What is the most likely effect of this?
Answer
A
an increase in gene flow between the bird populations
B
an increase in mutations in both bird populations
C
an increase in genetic drift between the bird populations
D
an increase in mutations in the island population
Explanation
The new sandbars and tiny islands may create stepping-stones that let birds move between the mainland and the island. When individuals move between populations and reproduce, they transfer alleles, increasing gene flow. The new land would not directly increase mutation rates, and genetic drift is random change in allele frequencies rather than movement between populations.
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