Stable eusociality via maternal manipulation when resistance is costless

Abstract

In many eusocial species, queens use pheromones to influence offspring to express worker phenotypes. While evidence suggests that queen pheromones are honest signals of the queens reproductive health, here I show that queens honest signaling can result from ancestral maternal manipulation. I develop a mathematical model to study the coevolution of maternal manipulation, offspring resistance to manipulation, and maternal resource allocation. I assume that (1) maternal manipulation causes offspring to be workers against offsprings interests; (2) offspring can resist at no direct cost, as is thought to be the case with pheromonal manipulation; and (3) the mother chooses how much resource to allocate to fertility and maternal care. In the coevolution of these traits, I find that maternal care decreases, thereby increasing the benefit that offspring obtain from help, which in the long run eliminates selection for resistance. Consequently, ancestral maternal manipulation yields stable eusociality despite costless resistance. Additionally, ancestral manipulation in the long run becomes honest signaling that induces offspring to help. These results indicate that both eusociality and its commonly associated queen honest signaling can be likely to originate from ancestral manipulation.