The illinois populations of the greater prairie chicken benefited when managers brought in prairie chickens from other populations. this restored genetic variation to the illinois populations through the process of

Gene Flow

Explanation:

In the population genetics, the gene flow which is also referred to as the allele flow is described as the transmission of the genetic alteration from one ends of the population to the other. If the amount of the flow tends to be high enough, then the respective populations are known to to have the equal allele frequencies and thus effectively can be termed as the single population.