Why might a population show low levels of genetic diversity?

A population may show low levels of genetic diversity when it was founded by a small number of individuals, a phenomenon known as the founder effect. This situation arises because the genetic variation of the new population will be limited to only the alleles present in those initial founders. When a population originates from just a few individuals, the gene pool is reduced, resulting in reduced genetic variation over generations.

This lack of diversity can lead to increased susceptibility to diseases and a reduced ability to adapt to environmental changes, as the genetic traits within the population are not sufficiently varied. Genetic drift can further exacerbate this situation, leading to the loss of alleles over time, especially in small populations.

In contrast, constant mutation processes, historical population size, and having many unrelated individuals are less likely to contribute to low genetic diversity in the same way. Large populations generally have more genetic variation simply due to a larger gene pool.