founder effect

The founder effect is an important cause of genetic drift in addition to natural selection and random drift. The founder effect is the difference between the gene pool of a population as a whole and that of a newly isolated population of the same species. The founder effect occurs when populations are started from a small number of pioneer individuals of one original population. Because of small sample size, the new population could have a much different genetic ratio than the original population. An example of the founder effect would be when a plant population results from a single seed.