During summer, low water levels cut off gene flow between these two.

Physical barriers to gene flow are usually, but not always, natural.

See below for environmental risks of gene flow among plants.

This will allow species to increase gene flow and help with migration.

The study also found that there is limited gene flow between the populations.

Such gene flow is less likely today because the populations are more separated.

Female choice can also play a role in hindering gene flow.

Or is base running a societal metaphor for gene flow?

Gene flow - The movement of genes from one population to another by individuals moving between the populations.

Until the agricultural revolution 10,000 years ago, people used to live in small populations with little gene flow between them.