Asymmetric interactions between hosts and symbionts. In mutualisms, the controlled partner, the symbiont, can diversify in strategies that can be either fully cooperative, less cooperative, or completely uncooperative, i.e. “cheating.” Cheaters may evolve into parasitic or commensal species. However, the controlling partner, the host, might also diversify its strategies to enforce or induce most of the symbiont individuals to be cooperative.