Cooperative breeding and the selection for information sharing among groupmates.

Abstract: Understanding variation in reproductive skew between and within cooperatively breeding species is a key aim of social evolution. However, tests of reproductive skew models give equivocal results, potentially because different models make different assumptions and some of the theoretical assumptions are wrong. Most models assume that both dominants and subordinates are perfectly informed, but animals likely have asymmetric imperfect information, since individuals know better their own quality and subordinates are freer to explore breeding options outside the group. To explore effects of dominants' uncertainty, we extended the standard concession model of skew with an explicit focus on subordinate quality, which we assume determines their outside options and influences their contribution to group productivity. Depending on how quality influences group productivity, dominants should prefer low- or high-quality subordinates. When subordinate quality correlates positively and strongly with group productivity, skew decreases with quality, otherwise skew increases with quality. The average concession offered to subordinates is greatest when dominants have imperfect information. In most cases dominants are selected to acquire information, whereas subordinates should restrict the information given to dominants, even though this may reduce the opportunities for cooperative breeding. Concessions always decrease with relatedness, so related subordinates would especially benefit from the dominant being uncertain about relatedness, potentially explaining why true kin recognition is rare in nature. Overall, our new predictions show that uncertainty can strongly influence evolutionary games and that incorporating it in skew models may to help explain patterns of cooperative breeding observed between and within species.

Significance statement: Great variation in reproductive skew exists among cooperative breeders, which current theory fails to predict. This suggests the need for more realistic models. The level of uncertainty about the fitness consequences of the decision to breed cooperatively or not can vary between dominants and subordinates, and among dominants of different species. Our theoretical study predicts that a dominant's level of information about the quality of a potential subordinate influences the optimal reproductive share and inclusive fitness. Furthermore, our work reveals that the link between a subordinate's outside options and their effect on group fecundity is extremely important in shaping reproductive decisions and information-related strategies. Related subordinates should conceal their kinship to the dominant, potentially preventing the evolution of kin recognition. We argue that empirical studies should strive to disentangle the various ways in which subordinates affect fitness, and examine the variation among individuals in their opportunities and abilities to help.

Supplementary information: The online version contains supplementary material available at 10.1007/s00265-025-03604-5.