When Resistance Is Useless: Policing and the Evolution of Reproductive Acquiescence in Insect Societies

Abstract

In social groups composed of kin, inclusive fitness benefits can favor greater cooperation. Alternatively, cooperation can be enforced through the policing of less cooperative individuals. Here, we show that the effect of policing can be twofold: not only can it directly suppress individual selfishness, it can also entirely remove the incentive for individuals to act selfishly in the first place. We term such individual restraint in response to socially imposed policing "acquiescence" and illustrate the concept using examples drawn from the social Hymenoptera (the ants, bees, and wasps). Inclusive fitness models confirm that when a policing system is in place, individuals should be less tempted to act selfishly. This is shown to have important consequences for the resolution of conflict within their societies. For example, it can explain why in many species very few workers attempt to reproduce and why immature females usually do not attempt to develop as queens rather than workers. Although our analyses are primarily focused on the social insects, our conclusions are likely to be general and to apply to other societies as well.

Altruism in insect societies and beyond: voluntary or enforced?

“…Similarly, Frank has argued for the importance of social control mechanisms in promoting cooperation in a wide range of systems [12]. Nevertheless, it is only recently that theoretical models have been developed that specifically determine the extent to which altruism in insect societies is enforced [7,13] and that enough empirical evidence has accumulated to test the predictions of these models [14]. Here we summarize this work.…”

“…Over the past few decades, several important coercive behaviours have been discovered in insect societies ( Figure 1) [5], ranging from the killing of worker-laid eggs [6] to preventing larvae from developing into queens via food control [1]. In inclusive fitness terms, such coercion promotes altruism because it reduces the benefit of attempting to reproduce directly relative to the benefit of rearing non-descendant kin [7,8]. That is, by hindering direct reproduction, social pressure causes individuals to acquiesce and thereby become more altruistic.…”

“…Acquiescence: a situation whereby coercion favours individuals to comply with the social norms of the group, even if this is not their first choice [7]. Altruism: an action that, on average, decreases the lifetime direct fitness of an actor and benefits one or more recipients [4].…”

“…How can this low level of relatedness result in societies in which fewer than one in 1000 workers attempts to lay eggs [16] or one in 10 000 female larvae develops into a queen [17]? Recent theory suggests that, in the absence of coercion, it cannot [7,13].…”

“…The reason becomes clear when we consider egg laying by workers [7,13]. In the social Hymenoptera, workers can lay haploid, male-destined eggs (Figure 2).…”