What type of selection might occur if a population is dramatically reduced in size?

The bottleneck effect refers to a significant reduction in the size of a population due to environmental events, such as natural disasters or human impacts, leading to a loss of genetic diversity. When a population experiences such a dramatic decrease in numbers, the genetic variation within the remaining members is typically reduced. This limitation can affect the population's ability to adapt to new environmental pressures because there are fewer alleles to provide a range of traits that may be beneficial for survival.

In the context of evolutionary processes, the bottleneck effect can lead to changes in allele frequencies and may increase the risk of inbreeding. It also shapes the evolutionary trajectory of the population and can result in particular traits becoming more prominent or less diverse, depending on which individuals survive and reproduce after the population is reduced. This is in contrast to directional, stabilizing, and disruptive selection, which describe the effects of selection pressures on variation within a larger population rather than the consequences of a population being sharply decreased in size.