An earthquake decimates a ground-squirrel population, killing 98% of the squirrels. The surviving population happens to have broader stripes, on average, than the initial population. If broadness of stripes is genetically determined, what effect has the ground-squirrel population experienced during the earthquake?

A) directional selection

B) disruptive selection

C) a founder event

D) a genetic bottleneck

D) a genetic bottleneck

Explanation:

Genetic bottleneck refers to the sudden reduction in the population size due to some adverse climatic factors such as natural calamities. It changes the allele frequencies since the survivor population mostly have different allele frequencies than the original population.

In the given example, an earthquake kills 98% of the squirrels. The survivor population exhibits different allele frequencies for the gene responsible for the thickness of stripes. Therefore, it represents a genetic bottleneck.