Founder

Founder Effect

The founder effect is a key concept in population genetics and evolutionary biology. It refers to the reduced genetic diversity that occurs when a population is descended from a small number of colonizing ancestors. This phenomenon can have significant implications for the genetic structure and evolutionary trajectory of populations.

Overview

The founder effect occurs when a new population is established by a very small number of individuals from a larger population. This small group of "founders" carries only a fraction of the genetic variation present in the original population. As a result, the new population may have reduced genetic diversity and may be subject to different evolutionary pressures than the original population.

Mechanism

The founder effect is a type of genetic drift, which is a mechanism of evolution that involves random changes in the frequency of alleles in a population. When a small group of individuals becomes isolated from a larger population, the alleles they carry may not be representative of the original population's genetic diversity. Over time, the genetic makeup of the new population can drift away from that of the original population.

Consequences

The founder effect can lead to several important consequences:

• Reduced Genetic Variation: The new population may have less genetic variation than the original population, which can affect its ability to adapt to changing environmental conditions.

• Increased Prevalence of Rare Alleles: Alleles that were rare in the original population may become more common in the new population if they were present in the founders.

• Inbreeding: With a smaller gene pool, the likelihood of inbreeding increases, which can lead to an increase in homozygosity and the expression of deleterious recessive traits.

Examples

One classic example of the founder effect is the population of Amish in the United States. The Amish community was founded by a small number of individuals, and as a result, certain genetic disorders, such as Ellis-van Creveld syndrome, are more prevalent in this population than in the general population.

Another example is the Galápagos Islands, where the isolation of small populations of finches led to the development of distinct species, a phenomenon that was crucial to Charles Darwin's formulation of the theory of natural selection.

Related Concepts

The founder effect is closely related to other concepts in population genetics, such as the bottleneck effect, which also involves a reduction in genetic diversity due to a significant decrease in population size.

See Also

• Genetic drift
• Population bottleneck
• Speciation
• Natural selection

References

• Mayr, E. (1963). Animal Species and Evolution. Harvard University Press.
• Templeton, A. R. (1980). "The theory of speciation via the founder principle." Genetics 94: 1011-1038.