Answer:
Allopatric speciation
Explanation:
Allopatric speciation is a type of speciation that takes place when a group of species are divided into two different groups which are separated from each another. In allopatric speciation, a geographic barrier such as a water body (river) or a mountain range forms and prevents the species from mating with each other. As the species are separated into two groups, each of them develops its own distinct traits based on the demands of their unique environment or the inherited traits of the group that are passed on to offspring.
With a certain species out of the food chain this leaves other animals population to dwindle because of them feeding off of the migrating animals. Meanwhile other plants and animals might flourish because these animals would no longer be a threat to their species.