Options for the question have not been provided. They are as follows:
migration
founder effect
temporal isolation
behavioral isolation
Answer:
founder effect
Step-by-step explanation:
In the given scenario a large population of finches got divided into many smaller populations. Each of these smaller populations inhabited a particular island and adapted according to the conditions of that island. Eventually, they evolved very differently from each other and formed new species. This is a classic case of founder effect where a small group of individuals breaks off from the bigger population and starts a new population in some other area. Since a limited number of individuals start the new population, some alleles can be absent in it which were found in the original population.