Extinction vortex

An extinction vortex is a self-reinforcing decline in a small population, in which demographic, genetic, or environmental effects intensify one another and raise extinction risk.

Allee effect: A decline in individual survival or reproduction as population density becomes very low. Reduced mating success or cooperation can start the demographic feedback that drives a vortex.
Population bottleneck: A sharp, temporary reduction in population size that leaves fewer individuals to reproduce. Bottlenecks can leave populations small enough for genetic and demographic feedbacks to begin.
Genetic rescue: An increase in population fitness after individuals from another population introduce new genetic variation. Gene flow can reduce inbreeding effects and interrupt a genetic feedback loop.
Florida panther: A population of pumas persisting in southern Florida, historically reduced and genetically isolated. Inbreeding-related problems prompted genetic introgression to improve population health.
Inbreeding depression: Reduced survival or reproduction caused by mating between genetically related individuals. Shrinking populations make related matings more common, weakening population growth.
Effective population size: The size of an idealized population experiencing the same genetic drift as a real population. It can be far smaller than the head count and better predicts genetic vulnerability.
Captive breeding: The managed reproduction of animals in human care to support conservation or reintroduction. Careful breeding can raise numbers while limiting further loss of genetic variation.
Devil's Hole pupfish: A critically endangered fish population confined to a single small pool in Nevada. Its tiny population makes environmental fluctuations and chance demographic events especially consequential.
Genetic drift: Random changes in allele frequencies, strongest in small populations. Drift removes genetic variation that could help a declining population adapt.
Genetic diversity: The variety of genetic differences within and among populations. Its loss can reduce adaptive potential and expose harmful genetic effects.

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