Honeybees are haplodiploid: fertilised eggs (diploid, 2N) become workers/queens, unfertilised eggs (haploid, N) become drones. A queen mates with many drones on a single nuptial flight (polyandry), storing sperm to father overlapping worker "patrilines" for the colony's life.
worker genotype = 1/2 queen allele + 1/2 one drone's (clonal) allele
Diversity ~ 1 - sum(patriline_i^2) (Simpson's index)
Inbreeding risk high when csd alleles match (diploid drones)
- Drone count — how many drones the queen mated with; more mates raise patriline count and colony-level diversity.
- Drone genetic spread — how different the drones' allele pools are from each other; wider spread increases effective diversity per mate.
- Colony size — number of worker offspring simulated, colour-coded by which patriline (drone father) they belong to.
- Selection pressure — how strongly breeders cull low-resistance patrilines each generation, raising average Varroa resistance but shrinking diversity.
Low mate number or closed breeding populations increase homozygosity at the complementary sex-determiner (csd) locus, producing sterile diploid drones — the honeybee's inbreeding depression signature.