Regulation of queen–worker conflict in bumble bee (Bombus terrestris) colonies

Abstract

In annual colonies of bumble-bees overt queen-worker conflict is limited to a distinct 'competition phase' (CPh). In unmanipulated Bombus terrestris colonies, the queen's switch to male production (the 'switch point', SP) accounted for only-22% of the variation in the onset of the CPh. In some colonies, the CPh even began before the SP. The CPh was more strongly correlated with the transition in queen production (r=0.79). Replacing the queen eggs with male eggs or doubling the number of workers in young colonies resulted in a significantly earlier onset of the CPh and a significantly earlier transition to queen production. Replacing queen eggs with female eggs did not have this effect. These manipulations did not affect the timing of the queen's switch from female to male production. These findings show that the mechanism underlying the queen-worker conflict in insect societies is more complex than previously appreciated. The onset of queen-worker conflict cannot be attributed simply to a single factor such as the queen's switch to male production or a decrease in queen inhibition. Rather, multiple cues are important.

Effect of the queen on worker reproduction and new queen production in the bumble beeBombus terrestris

“…Endler et al, 2004). In the bumble bee Bombus terrestris L., colonies reach a point (the competition point) at which the workers commence aggression and egg-laying and following which the first new queens eventually eclose (Duchateau and Velthuis, 1988;Bloch, 1999). There is a tight temporal link between the onset of Corresponding author: A.F.G.…”

“…There is a tight temporal link between the onset of Corresponding author: A.F.G. Bourke, a.bourke@uea.ac.uk * Manuscript editor: Stan Schneider worker reproduction and queen production, with the competition point predictably occurring c. 10 days after the queen lays the first diploid eggs that will develop as new queens (Duchateau and Velthuis, 1988;Bloch, 1999;Bortolotti et al, 2001;Alaux et al, 2004). A variety of evidence supports pheromonal queen regulation of worker reproduction and queen development, but the exact mechanisms are not fully resolved (Crespi, 1992;Kukuk, 1992;Bloch and Hefetz, 1999a;Cnaani et al, 2000;Bourke and Ratnieks, 2001;Duchateau et al, 2004), partly because the experimental evidence is not always consistent across different studies.…”

Drifting behaviour as an alternative reproductive strategy for social insect workers

“…Its annual colony life cycle consists of two contrasting phases with respect to intracolonial worker reproduction: some workers have activated ovaries in the early developmental stages of the colony ('social phase') but refrain from reproducing up to the end of the colony cycle ('competition phase') where they start to intensively compete with each other for male production [13][14][15][16][17]. Besides the well-studied occurrence of intracolonial reproduction, cases of heterocolonial reproduction by workers have been described [5,9].…”

Differential gene expression in queen–worker caste determination in bumble-bees

“…larvae capable of developing into adults of either caste) are irreversibly determined towards development as workers; if such a queen is absent, larvae develop as normal queens provided that, in their fourth (last) instar, they also receive sufficient food (Rö seler 1991; Cnaani & Hefetz 2001;Cnaani et al 1997Cnaani et al , 2000Hartfelder et al 2000;Bortolotti et al 2001;Bourke & Ratnieks 2001;Pereboom et al 2003). In addition, B. terrestris workers can be reproductive, since the end of the annual colony cycle (the so-called competition phase) is characterized by the emergence of dominant, reproductive (egg-laying) workers and subordinate, non-reproductive workers (Duchateau & Velthuis 1988;Bloch 1999;Bloch & Hefetz 1999). Therefore, by comparing the gene expression profiles underlying differences between adult queens and workers with those underlying differences between reproductive and non-reproductive adult workers, it is, in principle, possible to distinguish between differences owing to the presence or absence of reproduction and those owing to caste membership per se.…”