Founder Effect & Genetic Bottleneck Simulator

Founder Effect

Founder population size 8

Island carrying capacity 90

Generation speed 1.5/s

Alleles left (island/mainland)

–

Heterozygosity

–

Inbreeding risk

–

Generation

How it works

The left cluster is a large, stable "mainland" gene pool: every dot is one individual, coloured by which of eight alleles it carries at a single locus, with realistic uneven frequencies (a few common alleles, several rare ones). When a handful of individuals — the founders — colonise a new island, they can only carry the alleles that happened to be in their small sample. Rare alleles are easily missed entirely, and every later generation is built by re-sampling with replacement from the previous one, so chance (genetic drift) keeps eroding whatever diversity survived the founding event.

H = 1 − Σ pᵢ²          (expected heterozygosity)
F_t = 1 − (1 − 1/(2·Ne))^t   (inbreeding coefficient)

Founder population size — how many individuals start the island colony; small founder groups sample only a slice of the mainland's alleles and drift faster (Ne in the formula above is approximated by this count).
Island carrying capacity — the population ceiling the colony grows toward; a low ceiling keeps drift strong forever, a high one lets diversity stabilise sooner once the colony fills it.
Generation speed — how fast auto-advance steps through Wright–Fisher generations once "Auto-advance" is on.
Found New Colony — redraws a fresh founder sample from the mainland and resets the generation clock, so you can compare a lucky founding event against an unlucky one.

Real-world relevance: this is the same mechanism behind the low genetic diversity of cheetahs, northern elephant seals (hunted to under 30 individuals) and many island-endemic species — a population squeezed through a narrow founding or near-extinction bottleneck keeps only a fraction of its ancestral gene pool, raising the risk of inbreeding depression even after numbers recover.

Mainland pop.Island colony

A B C D E F G H

⚠ Couldn't load the 3D engineThree.js failed to load from the CDN. Check your connection and reload.