Answer:
Allopatric speciation
Explanation:
Allopatric speciation is a form of gradual process of evolution, in which a population of a common species evolves to form different species as a result of being isolated from each other geographically. As a result of the separation of one population of rabbits from the others caused by the river, over time, forces of natural selection and genetic drift will cause the two populations to evolve differently and thereby resulting in two new different species with genetic differences.