Respuesta :
The four examples listed above could all be responsible in the change in a gene pool also called founder effect. The founder effect is the reduction of genetic variation that occurs when a new population is started by a few members of the original population. Under the founder effect, a small population of a species is physically isolated from the original population,and the isolation prevents breeding between the two populations.
Migration or gene flow is any movement of individuals, and/or the transfer of alleles or genes from one population to another.
Answer is gene flow.