Relatedness Ratios in Haplodiploidy
Relatedness is used to calculate the strength of kin selection (via Hamilton's rule). The haplodiploidy hypothesis states that the unusual 3/4 relatedness coefficient amongst full haplodiploid sisters is responsible for the frequency of evolution of eusocial behavior in hymenoptera.
In normal sexual reproduction the father has two sets of chromosomes, and crossing over takes place between the chromatids of each pair during the meiosis which produces the sperm. Therefore, the sperms are not identical, because in each chromosome of a pair there will be different alleles at many of the loci. But when the father is haploid all the sperm will be identical (except for a small number where gene mutations have taken place in the germ line). So, as long as all the female queen mates only with one male, all the female offspring will inherit the male's chromosome 100% intact. In fact in hymenoptera, the males almost all produce enough sperm to last the female for a whole lifetime.
Relatedness coefficients in haplodiploid organisms are as follows.
| Sex | Daughter | Son | Mother | Father | Full Sister | Full Brother |
|---|---|---|---|---|---|---|
| Female | 1/2 | 1/2 | 1/2 | 1/2 | 3/4 | 1/4 |
| Male | 1 | 1 | 1/2 | 1/2 |
Read more about this topic: Haplodiploid Sex-determination System
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