Final answer:
Gene flow is the process that can rapidly offset the effects of genetic isolation by transferring alleles between populations, leading to new genetic variation and altered allele frequencies.
Step-by-step explanation:
The process that can rapidly offset the effects of genetic isolation when two populations come into secondary contact is gene flow. Gene flow refers to the transfer of alleles or genes from one population to another. It is an evolutionary mechanism that can introduce new genetic variation and alter allele frequencies in a population.
For example, if individuals from one population migrate to another and reproduce, their genes can be incorporated into the gene pool of the new population, thus reducing the genetic differences between the two populations.
Mutation is another source of genetic variation, where random changes in DNA sequences can result in new alleles. However, mutation alone usually introduces new variation at a much slower rate compared to gene flow.
Furthermore, genetic drift is a stochastic process that can lead to changes in allele frequencies in a population, particularly in small populations, rather than offsetting genetic isolation with a flow of new genes. Natural selection can also lead to changes in allele frequencies based on the differential survival and reproduction of individuals with certain heritable traits.