# Founder effect

> The founder effect is the loss of genetic diversity when a new population is started from a few individuals, so it carries only a sample of the source population's alleles.

- Canonical: https://genetixbay.com/knowledge/glossary/founder-effect.html
- Also written: founder population, founder effects, founder event
- Glossary category: Genetics and breeding · Evidence: Established
- Status: Draft: awaiting expert review · Updated: 2026-10-31
- Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay cannabis glossary"

The founder effect is reduced and shifted [genetic diversity](https://genetixbay.com/knowledge/glossary/gene-pool.md) in a population started by a small number of individuals. The founders carry only part of the source population's [alleles](https://genetixbay.com/knowledge/glossary/allele.md), and by chance some rare alleles become common in the new population while others disappear.

## In practice

Many [cannabis seed](https://genetixbay.com/knowledge/glossary/achene.md) lines began as founder events. A traveller brought back seed from a few plants of a [landrace](https://genetixbay.com/knowledge/glossary/landrace.md); a breeder started a line from one exceptional female and one male; a [heirloom](https://genetixbay.com/knowledge/glossary/heirloom.md) was passed on as a single packet. Each of these new populations reflects its few founders, not the full landrace.

That is why two "Afghan" lines from different collections can differ markedly, and why a line kept outside its source region may drift away from the original type. Records of how many plants founded a line, and from where, help breeders judge how representative it is.

## Don't confuse with

- **Genetic bottleneck**: a crash in numbers within an existing population; the founder effect is the start of a new one.
- **Selection**: founders chosen for traits are both a selection and a founder event.
- **Landrace**: the source population, typically far more diverse than lines founded from it.

## Related terms

[Genetic bottleneck](https://genetixbay.com/knowledge/glossary/genetic-bottleneck.md), [Genetic drift](https://genetixbay.com/knowledge/glossary/genetic-drift.md), [Gene pool](https://genetixbay.com/knowledge/glossary/gene-pool.md), [Landrace](https://genetixbay.com/knowledge/glossary/landrace.md), [Heirloom](https://genetixbay.com/knowledge/glossary/heirloom.md)

## Read more

- [How hybrid 'strains' emerged](https://genetixbay.com/knowledge/genetics-history/how-hybrid-strains-emerged.md)

## Sources

1. Falconer DS, Mackay TFC. 1996. Introduction to Quantitative Genetics, 4th edition. Longman, Harlow. ISBN 978-0-582-24302-6