Answer:
A genetic bottleneck
Step-by-step explanation:
A genetic bottleneck occurs as an event that drastically reduces the size of a particular population producing a decrease in the gene pool as a lot of the gene variants is taken along with it.
The bottleneck effect may be caused by various events, such as an environmental disaster, excessive hunting etc.
The genetic bottleneck occurs when a gene pool is narrowed to a fraction of its former diversity and then taking along with it a lot of genetic variants leading to the increased frequency of the broader striped population.