Drifting behaviour as an alternative reproductive strategy for social insect workers

Abstract

Restricted reproduction is traditionally posited as the defining feature of eusocial insect workers. The discovery of worker reproduction in foreign colonies challenges this view and suggests that workers' potential to pursue selfish interests may be higher than previously believed. However, whether such reproductive behaviour truly relies on a reproductive decision is still unknown. Workers' reproductive decisions thus need to be investigated to assess the extent of workers' reproductive options. Here, we show in the bumblebee Bombus terrestris that drifting is a distinct strategy by which fertile workers circumvent competition in their nest and reproduce in foreign colonies. By monitoring workers' movements between colonies, we show that drifting is a remarkably dynamic behaviour, widely expressed by both fertile and infertile workers. We demonstrate that a high fertility is, however, central in determining the propensity of workers to enter foreign colonies as well as their subsequent reproduction in host colonies. Moreover, our study shows that the drifting of fertile workers reflects complex decision-making processes associated with in-nest reproductive competition. This novel finding therefore adds to our modern conception of cooperation by showing the previously overlooked importance of alternative strategies which enable workers to assert their reproductive interests.

Worker thelytoky allows requeening of orphaned colonies but increases susceptibility to reproductive cheating in an ant

“…Alternatively, orphaned colonies may be 557 a source of social parasitic workers if the intense reproductive conflicts between workers 558 result in some workers absconding or being expelled from the colony. That is, social 559 parasitism may be a side effect of the massive worker reproduction in orphaned colonies 560 rather than an evolved parasitic strategy (Blacher et al, 2013). Our data support this 561 hypothesis to some extent as we found gynes produced by workers from the orphaned colony 562 in one of the four queenright colonies that produced gynes (colony 4-QR-a).…”

“…This is the 538 first unambiguous demonstration of intra-specific social parasitism in C. cursor under natural 539 conditions, and it corroborates the finding of a previous study under laboratory conditions in 540 which foreign workers present in one colony produced a disproportionably high number of 541 gynes (Blacher et al, 2013). Orphaned colonies may be more 546 susceptible to social parasitism by foreign workers.…”

Go High or Go Low? Adaptive Evolution of High and Low Relatedness Societies in Social Hymenoptera

“…distinguishable from unicoloniality in ants (e.g., 42% of workers in A. mellifera nests are aliens; Pfeiffer and Crailsheim, 1998, 59% of marked workers in B. terrestris at least visit a foreign nest; Blacher et al, 2013, and 56% of female Polistes canadensis drift; Sumner et al, 2007). Overall, one evolutionary pathway to unicoloniality may be as simple as strong selection through social heterosis for high levels of drifting.…”

Should I stay or should I go: honeybee drifting behaviour as a function of parasitism

“…However, drifting behaviour, described as the movement of individuals from their own nest to another, sometimes occurs either as a reproductive strategy or as an accidental phenomenon. On one hand, nest drifting in some eusocial insect species has been shown to represent an alternative reproductive strategy to maximise the drifter's fitness either by contributing to brood raising in several related nests or by directly laying eggs in foreign nests (Neumann et al 2003;Lopez-Vaamonde et al 2004;Nanork et al 2005;Nanork et al 2007;Sumner et al 2007;Chapman et al 2010;Takahashi et al 2010;Blacher et al 2013;O'Connor et al 2013;Zanette et al 2014). On the other hand, nest drifting can be an accidental phenomenon that is not deliberate but instead is the consequence of orientation errors during orientation or foraging flights, as frequently found in the honeybee, Apis mellifera (Free 1958;Pfeiffer and Crailsheim 1998;Neumann et al 2000).…”