In a monogamous haplodiploid social insect colony, sterile workers assist the queen in producing additional sisters instead of reproducing themselves. According to Hamilton’s rule, altruistic behaviour is favoured when the genetic benefit to relatives (weighted by coefficient of relatedness, r) exceeds the cost (c) to the actor.
If a worker helps the queen raise three daughters instead of producing two of her own, then based on Hamilton’s rule, will helping behaviour evolve?
(Assume genetic unit = number of offsprings weighted by r as a measure of inclusive fitness)

Correct option is A

Correct Answer:
(1) Yes, because rb = 2.25 genetic units and c = 1 genetic unit
Explanation:
In haplodiploid species, full sisters share a relatedness of r = 0.75, while a worker is related to her own offspring by r = 0.5.
Benefit (rb):
Helping to raise 3 sisters → 3 × 0.75 = 2.25 genetic units
Cost (c):
Not producing 2 own offspring → 2 × 0.5 = 1 genetic unit
Since rb > c (2.25 > 1), Hamilton’s rule is satisfied and helping behaviour will evolve.
Information Booster :
· Haplodiploidy leads to unusually high relatedness among sisters.
· This genetic asymmetry favours the evolution of eusociality.
· Hamilton’s rule provides a quantitative framework for kin selection.
· Many ants, bees, and wasps show worker altruism driven by inclusive fitness gains.
Additional Information (Incorrect Options):
Option 2: Incorrect relatedness calculation; sisters in haplodiploids have r = 0.75, not 0.125.
Option 3: Incorrect—high r (not low) strengthens kin selection.
Option 4: Incorrect—haplodiploidy is one of the strongest systems supporting kin selection.