In a hypothetical South American bird species, 95% of individuals have red feathers, and 5% have brilliant purple plumage. On the nearest oceanic island, all birds of this species are purple. Which of the following phenomena is the most likely explanation for this pattern?

a. founder effect

b. plate tectonics

c. atavism

d. homoplasy

a) Founder effect

Explanation:

Founder effect: Small group of individuals separates from large population, and establishes a colony in a new place. Smaller new population won't have as much genetic variation as original, larger population. The allelle frequencies in the new population will be different than the original population.

For example: Few people leave a population and become founders of separate island.

As in the given scenario, Founder effect is the most likely explanation for this pattern.