Answer:
Such an event would be an example of the founder effect.
Step-by-step explanation:
Genetic drift is an evolutionary mechanism in which the allelic frequencies in a population change through many generations. Its effects are harder in a small-sized population.
Genetic drift results in some alleles loss, even those that are beneficial for the population, and the fixation of some other alleles by an increase in their frequencies. The final consequence is to randomly attach one of the alleles.
Genetic drift has important effects on a population when this last one reduces its size dramatically because of a disaster -bottleneck effect- or because of a population split -founder effect-.
The founder effect is a special case of genetic drift. The new population derives from a small number of founder individuals coming from a bigger ancestral population, that established in a new environment. This subgroup carries with them some genetic information that they share with their original population. Over time, some genes can be lost or they can increase in frequency. This might cause reduced genetic variability and enhance the possibilities of a peculiar allelic composition. The new population can be very different from the original one, not only in their genotypes but also in their phenotypes. In some cases, these differences can lead to speciation.