Answer:
Step-by-step explanation:
The situation given in the question can be an example of "Divergent Evolution" which can be described as the formation of different or new species because of environmental changes or changes in the habitat.
The isolation between the organisms from the mainland and the islands over generations lead to the genetic exchange getting cut off and therefore leads to the evolution of the different species since there is no interaction between them and their environments are also different. This results in new species through adaptation over time.
I hope this answer helps.