title: Chemical communication is not sufficient to explain reproductive inhibition in the bumblebeeBombus impatiens.
abstract: Reproductive division of labour is a hallmark of eusociality, but disentangling the underlying proximate mechanisms can be challenging. In bumblebees, workers isolated from the queen can activate their ovaries and lay haploid, male eggs. We investigated if volatile, contact, visual or behavioural cues produced by the queen or brood mediate reproductive dominance inBombus impatiens.Exposure to queen-produced volatiles, brood-produced volatiles and direct contact with pupae did not reduce worker ovary activation; only direct contact with the queen could reduce ovary activation. We evaluated behaviour, physiology and gene expression patterns in workers that were reared in chambers with all stages of brood and a free queen, caged queen (where workers could contact the queen, but the queen was unable to initiate interactions) or no queen. Workers housed with a caged queen or no queen fully activated their ovaries, whereas ovary activation in workers housed with a free queen was completely inhibited. The caged queen marginally reduced worker aggression and expression of an aggression-associated gene relative to queenless workers. Thus, queen-initiated behavioural interactions appear necessary to establish reproductive dominance. Queen-produced chemical cues may function secondarily in a context-specific manner to augment behavioural cues, as reliable or honest signal.
authors.affiliation: Department of Entomology, Center for Pollinator Research, Center for Chemical Ecology , The Pennsylvania State University , University Park, PA 16802 , USA.
authors.forename: Mario
authors.initials: M
authors.lastname: Padilla
authors.affiliation: Department of Entomology, Center for Pollinator Research, Center for Chemical Ecology , The Pennsylvania State University , University Park, PA 16802 , USA.
authors.forename: Etya
authors.initials: E
authors.lastname: Amsalem
authors.affiliation: Department of Statistics, Huck Institutes of Life Sciences, Clinical and Translational Sciences Institute , The Pennsylvania State University , University Park, PA 16802 , USA.
authors.forename: Naomi
authors.initials: N
authors.lastname: Altman
authors.affiliation: Department of Zoology, George S. Wise Faculty of Life Sciences , Tel Aviv University , Tel Aviv , Israel.
authors.forename: Abraham
authors.initials: A
authors.lastname: Hefetz
authors.affiliation: Department of Entomology, Center for Pollinator Research, Center for Chemical Ecology , The Pennsylvania State University , University Park, PA 16802 , USA.
authors.forename: Christina M
authors.identifier: 0000-0001-5738-1201
authors.initials: CM
authors.lastname: Grozinger
keywords: altruism; behaviour; chemical communication; division of labour; eusocial; pheromone