What type of evolutionary process is exemplified by the Founder's effect?

The Founder's effect is a specific type of genetic drift that occurs when a small group of individuals establishes a new population. This new population carries only a fraction of the genetic diversity of the original population, leading to a situation where certain alleles may become more prevalent simply due to chance.

In the case of the Founder's effect, the initial settlers (the "founders") may possess different allele frequencies than the larger source population, resulting in a genetic makeup that might not be representative of the source population. This reduced genetic variation can significantly impact the evolutionary trajectory of the new population, as certain traits may become fixed or lost more rapidly due to the limited gene pool.

The other options—natural selection, gene flow, and sexual selection—pertain to mechanisms of evolution that involve different processes. Natural selection involves the differential survival and reproduction of individuals due to differences in phenotype, gene flow describes the transfer of alleles into or out of a population due to migration, and sexual selection is a form of natural selection related to reproductive success. However, these do not describe the random changes in allele frequency associated with the founding of a new population, which is characteristic of genetic drift.