The Key Consequence: Sister-Sister Relatedness

The ultimate consequence of haplodiploidy is that female workers are genetically more closely related to their sisters than to their own offspring. Here’s why:

• In a colony with a single queen who has mated only once, sisters share, on average, 75% (r = 0.75) of their genes with each other, because they all receive identical genes from their haploid father and half their genes from their mother.

• By contrast, a female is related to her own offspring by only 50% (r = 0.5), which is the typical parent-offspring relatedness in diploid organisms.

This unusually high sister-sister relatedness makes it evolutionarily advantageous for female workers to help raise their sisters (the queen’s offspring) rather than producing their own offspring. This is a key factor in the evolution of eusociality and the selfless behavior seen in worker bees and ants, where individuals forego reproduction to help the colony.

Notable Implications

• This system does not guarantee more males than females in a colony, nor does it inherently make females behaviorally more dominant, although division of labor is common.

• The relatedness structure is what drives kin selection and the evolution of worker sterility and cooperation.

Correct answer:
(2) a female is genetically more closely related to her sister than to her own offspring