Answer:
Founder effect
Step-by-step explanation:
Founder effect was first outline by Ernst Mayr in 1942 using existing theoretical works, founder effect is a special case of a random genetic drift in the population gene which leads to loss of genetic variation that occurs when a new population ( that consist of few individual) becomes isolated from main pool, this new few individuals may establish a new population whose gene is different from the original population both in terms of its phenotype and phenotype
example is the Afrikaner population of Dutch settlers in South Africa