There are many sources of genetic variability in a population:

The world's plantations of cocoa are short on genetic variability.

In this area, the greatest genetic variability in the world was found.

There are so few wolves that they have lost genetic variability.

In small populations where genetic variability is low, individuals are more genetically similar.

Together they form a monophyletic group, with very low genetic variability.

Because of high genetic variability, seeds may have different characteristics compared to the parent plant.

Since their numbers are low there is a high risk of them losing too much genetic variability to survive.

The lack of genetic variability created a susceptible host population for the organism.

If a population has no genetic variability, scientists say, it cannot evolve through natural selection in response to long-term environmental changes.