Answer:
A. an Allee effect.
Step-by-step explanation:
Allee effect: In biology, the term "allee effect" is described as one of the phenomena which are distinguished as a specific correlation that exists between the mean of individuals fitness related to a particular species or population and the population density or size.
The main cause of the allee effect is the genetic mechanism.
In the question above, the given statement signifies an allee effect.