Inbreeding
Inbreeding tracking is essential for maintaining genetic diversity and colony vitality. BeePass calculates the inbreeding coefficient from the pedigree and helps you make informed mating decisions.
Inbreeding Coefficient
The inbreeding coefficient (F) measures the probability that both alleles at a gene locus in an individual are identical by descent (inherited from the same ancestor). It is calculated from the A⁻¹ matrix (inverse of the additive genetic relationship matrix).
BeePass uses the AINV-honeybees v20 package, which implements the Brascamp & Bijma (2014) algorithm specifically designed for honeybees.
Honeybee-Specific Challenges
Inbreeding calculation in honeybees is fundamentally different from mammals:
- Haplo-diploidy — Drones (males) are haploid: they carry only one set of chromosomes, inherited entirely from their mother. Classical inbreeding formulas (Wright, 1922) do not apply directly.
- Polyandry — The queen mates with 10 to 20 drones. Workers in the same colony are a mix of half-sisters and super-sisters (same drone father).
- Sex alleles (CSD) — In honeybees, sex is determined by the CSD locus. If both alleles are identical (homozygosity), the larva becomes a diploid male, which is eliminated by the workers. Higher inbreeding increases the proportion of these sterile diploid males.
BeePass uses AINV-honeybees v20 (Brascamp & Bijma, 2014), a dedicated module for computing the inverse relationship matrix for honeybees. This module accounts for haplo-diploidy and polyandry in coefficient calculations.
Interpretation
| Coefficient F | Meaning | Typical relationship |
|---|---|---|
| 0% | No known shared ancestors | Unrelated lines |
| 6.25% | Distant shared ancestors | Half-siblings |
| 12.5% | Close shared ancestors | First cousins |
| 25% | Strong relatedness | Parent-offspring |
Target: keep the inbreeding coefficient below 10% in your breeding programme.
Avoiding Inbreeding
Several strategies help limit inbreeding:
- Diversify sire groups — Use drones from lineages unrelated to your queens.
- Vary drone sources — Exchange drone mother queens with other breeders.
- Check the pedigree — Before every mating decision, review the pedigree tree over 5 to 7 generations to detect common ancestors.
- Use the Index BeePass — Compare reference queen pedigrees to identify complementary lineages.
Inbreeding above 12.5% leads to inbreeding depression: reduced colony vitality, lower disease resistance, increased diploid males (non-viable), and decreased reproductive success.
See also:
- BLUP — Overview — The computation pipeline and relationship matrix
- Reliability (r²) — Impact of pedigree on accuracy
- Genetic Passport — The pedigree tree in the passport