Female infidelity promotes male cooperation in collective predator defence or sharing of resources

Revealing the adaptive value of mate choice and female preference for ornamented males has been one of the great challenges to sexual selection. While female choice for direct benefits is considered important in species with biparental care, most theory h as focused on female choice for male genetic quality. These theories assume that offspring will inherit attractiveness or viability from their fathers, and such indirect genetic benefits have been used to explain the widespread occurrence of extra-pair pa ternity in socially monogamous systems. Recent theoretical and empirical research, however, supports the idea that direct costs of extra-pair matings (through e.g., reduced paternal care) may generally outweigh the indirect benefits. The current standing theory is therefore void of a coherent explanation for female infidelity. This project proposes and explores a mechanism that will fill this theoretical gap. We hypothesize that infidelity provides direct benefits to females because it may enhance male cooperation in collective predator defence or sharing of resources. In essence, a male will invest more in collective duties, such as vigilance and alarm calls, when he sires offspring in different nests. The incentive to monopolize resources may also dec rease, leaving more time for offspring care. In the proposal, we illustrate the logic of this hypothesis with a conceptual model, and show how females may manipulate male territorial investment and enhance offspring production. Furthermore, we show that t hese strategies will evolve and are evolutionarily stable for common parameter regions. The project aims at developing this hypothesis into a theoretical framework where female mating behaviour, male cooperative investment, and aggregation tendencies co-e volve.