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? an increase in mutations in both bird populations an increase in gene flow between the bird populations an increase in genetic drift between the bird populations an increase in mutations in the island population