Evolution of eusociality in termites driven by carbon-nitrogen imbalance

Termites feed on dead plant material, of which the carbon/nitrogen ratio is much higher than termite tissues. We propose a hypothesis that this extreme carbon/nitrogen ratio of the resources has driven the evolution of eusociality in termites. Because the carbon/nitrogen ratio required for reproduction is much lower than the resource carbon/nitrogen ratio, termites inevitably have excess carbon, which in turn may be utilized as an energy source to gain indirect fitness benefit through altruistic activities. We construct a kin-selection model in which the actor seeks the best resource allocation to altruism vs. selfish reproduction given fixed amounts of nitrogen and carbon. We show that the optimal allocation to altruism is positively correlated with the resource carbon/nitrogen ratio if altruism is carbon-consuming relative to selfish reproduction.