Answer:
After the bottleneck effect, some alleles may be extinct from the population. These alleles may or may not provide adaptive characteristics to the individual in relation to the environment.
Explanation:
The bottleneck effect occurs when changes occur in the environment, so as to dramatically reduce the size of a population. The name “bottleneck effect” stems from the fact that only part of the population resists a certain pressure from the environment.
It is worth noting, however, that the bottleneck effect does not seek to select the most adapted organisms, as in natural selection. Organisms that survive change are randomly selected in a matter of "luck." Thus, we have variations in allelic frequencies, because different individuals will be selected, regardless of their adaptive characteristics. In such cases, until the population recovers and its initial size increases, it will be possible to notice a loss of genetic variability.
An example of a bottleneck effect is the case of prairie grouse living in the prairies of the United States. Throughout the nineteenth and twentieth centuries, these animals had their habitat completely destroyed to make way for crops and pastures. The impact of human actions was so great that in 1993 only 50 individuals of this species were found, a considerable drop in the number of a population that was previously represented by millions of animals. The surviving birds had little genetic variability, and their eggs had little hatching index, suggesting that in this case there was an increase in alleles related to characteristics that reduce the reproduction rate (deleterious alleles).
