Genetic Rescue Simulator (2D)

Population Parameters

Effective population size N_e 50

Inbreeding load B (lethal equivalents) 6.0

Carrying capacity K 150

Simulation speed 1.0×

Genetic Rescue

Unrelated immigrants per event 10

Live Readouts

Heterozygosity H

100.0%

Inbreeding coeff. F

0.0%

Mean fitness w

100.0%

Population N

Generation t

Rescue events

How it works

In a closed population of effective size N_e, random mating loses heterozygosity every generation through genetic drift:

H(t) = H0 · (1 − 1/(2·Ne))^t
F(t) = 1 − H(t)/H0            (inbreeding coefficient)
w(t) = exp(−B · F(t))         (mean fitness, B = lethal equivalents)
dN/dt = rmax · w · N · (1 − N/K)   (fitness-scaled logistic growth)

As F rises, recessive deleterious alleles are exposed in homozygous form (inbreeding depression), pulling fitness w toward zero and slowing or reversing population growth — the mechanism behind real declines such as the Florida panther and Isle Royale wolves.

Genetic rescue introduces m unrelated immigrants (assumed to carry the source population's full heterozygosity, H = H0) into the population of N individuals. Gene flow instantly raises mean heterozygosity by simple additive mixing:

H_new = (N · H + m · H0) / (N + m)

This is exactly what happened when eight Texas pumas were released into the inbred Florida panther population in 1995: heterozygosity rose, inbreeding-linked defects fell, and the population's growth rate recovered within a few generations.

N_e slider — smaller effective population size means faster drift and faster heterozygosity loss.
B slider — the inbreeding load; higher B means each unit of inbreeding costs more fitness.
Introduce Immigrants — a genetic rescue event; watch H jump, F fall, and growth resume.
Drag the top cluster panel — rotates the population cluster (2D projection of a 3D arrangement), like an orbit camera.

Low heterozygosity (inbred) High heterozygosity (diverse) Recent immigrant

drag to rotate cluster