What is the difference between 'the bottleneck effect' and 'the founder effect'?

Question

I know they are both caused by genetic drift but what's the difference?

Answer 1

DISASTERS such as earthquakes, floods, or fires may reduce the size of a population drastically, killing victims unselectively. The result is that the small surviving population is unlikely to be representative of the original population in its genetic makeup - a situation known as the BOTTLENECK EFFECT.  GENETIC DRIFT caused by bottlenecking may have been important in the early evolution of human populations when calamities decimated tribes. The gene pool of each surviving population may have been, just by chance, quite different from that of the larger population that predated the catastrophe.

The FOUNDER EFFECT refers to the loss of genetic variation when a new colony is established by a very small number of individuals from a larger population.  In humans, founder effects can arise from cultural isolation, and inevitably, endogamy (i.e., marriage restricted to culturally or racially similar individuals).  The new population is often very small, so it shows increased sensitivity to GENETIC DRIFT, an increase in inbreeding, and relatively low genetic variation.

A population BOTTLENECK may also cause a FOUNDER EFFECT, even though it is not strictly a new population.

The essential difference between bottleneck and founder effects is that a bottleneck is a subpopulation caused when a natural disaster reduces the size of an original larger population, while a founder establishes a subpopulation as a new colony drawn from a larger population.

There should be no genetic selectional differences between a founder colony and a bottleneck, although a founder colony is likely to be a more robust subpopulation, in that it is able to pioneer a new geographical niche, while a bottleneck is likely to be a more robust subpopulation in that it was able to survive a disaster.

Answer 2

A population bottleneck (or genetic bottleneck) is an evolutionary event in which a significant percentage of a population or species is killed or otherwise prevented from reproducing, and the population is reduced by 50% or more, often by several orders of magnitude.[1]

Population bottlenecks increase genetic drift, as the rate of drift is inversely proportional to the population size. They also increase inbreeding due to the reduced pool of possible mates (see small population size).

A slightly different sort of genetic bottleneck can occur if a small group becomes reproductively separated from the main population. This is called a founder effect.

A founder effect occurs when a new colony is started by a few members of the original population. This small population size means that the colony may have:

reduced genetic variation from the original population.

a non-random sample of the genes in the original population.

An example of a bottleneck:

Northern elephant seals have reduced genetic variation probably because of a population bottleneck humans inflicted on them in the 1890s. Hunting reduced their population size to as few as 20 individuals at the end of the 19th century. Their population has since rebounded to over 30,000—but their genes still carry the marks of this bottleneck: they have much less genetic variation than a population of southern elephant seals that was not so intensely hunted.

An example of founder effect:

For example, the Afrikaner population of Dutch settlers in South Africa is descended mainly from a few colonists. Today, the Afrikaner population has an unusually high frequency of the gene that causes Huntington’s disease, because those original Dutch colonists just happened to carry that gene with unusually high frequency. This effect is easy to recognize in genetic diseases, but of course, the frequencies of all sorts of genes are affected by founder events.

Answer 3

They both cause genetic drift, they aren't caused by it. :)

Bottleneck effect is when there's something that either kills the majority of the population or just prevents it from reproducing. This creates genetic drift because the likelihood of gene prominence changing is much higher in a small population.

The Founder Effect is a type of Bottleneck effect. It is when a small amount of individuals starts a population usually due to migration.