What is most likely to happen to a new advantageous allele in a small population subject to both selection and genetic drift?

In a small population, the effects of genetic drift can be quite pronounced, often overwhelming the influence of selection. Genetic drift refers to random fluctuations in allele frequencies that can occur due to chance events, especially when the population size is small. This randomness can lead to situations where even advantageous alleles might not persist over time due to the changes in allele frequency that occur randomly through drift.

In this context, an advantageous allele may provide some benefit to the organism, but in a small population, it may not become widely established if drift causes it to be lost. For instance, suppose a few individuals carry this beneficial allele; if by chance those individuals do not reproduce successfully due to random variations in survival or reproduction unrelated to the allele’s advantage, the allele could be lost entirely from the population. Conversely, alleles that confer no advantage can also be lost or become fixed through this same random process.

Therefore, while selection typically works to enhance the frequency of advantageous alleles, the effect of genetic drift in a small population can lead to the allele going extinct, particularly if its initial frequency is low or if the selective pressure is not overwhelmingly strong. This dynamic highlights the balance between selection and drift and demonstrates the complexities inherent in evolutionary processes in small populations.