What genetic phenomenon is characterized by low variation due to the isolation of a smaller group of organisms?

The phenomenon characterized by low genetic variation due to the isolation of a smaller group of organisms is known as the Founder Effect. This occurs when a new population is established by a very small number of individuals from a larger population. When these founders establish a new population, they may possess only a fraction of the genetic diversity found in the original population. As a result, certain alleles may be overrepresented or underrepresented in the new population compared to the source population.

The limited genetic diversity can lead to increased susceptibility to diseases and environmental changes, as there is less variation for natural selection to act upon. The Founder Effect is particularly significant in populations that become geographically isolated, where the genetic makeup is heavily influenced by the founders' traits. Thus, over time, the small initial group can give rise to a population that reflects the limited genetic variation of its founders.