title: Antimicrobial defences increase with sociality in bees.
abstract: Evidence for the antiquity and importance of microbial pathogens as selective agents is found in the proliferation of antimicrobial defences throughout the animal kingdom. Social insects, typified by crowding and often by low genetic variation, have high probabilities of disease transmission and eusocial Hymenoptera may be particularly vulnerable because of haplodiploidy. Mechanisms they employ to reduce the risk of disease include antimicrobial secretions which are particularly important primary barriers to infection. However, until now, whether or not there is selection for stronger antimicrobial secretions when the risk of disease increases because of sociality has not been tested. Here, we present evidence that the production of progressively stronger antimicrobial compounds was critical to the evolution of sociality in bees. We found that increases in group size and genetic relatedness were strongly correlated with increasing antimicrobial strength. The antimicrobials of even the most primitive semi-social species were an order of magnitude stronger that those of solitary species, suggesting a point of no return, beyond which disease control was essential. Our results suggest that selection by microbial pathogens was critical to the evolution of sociality and required the production of strong, front-line antimicrobial defences.
authors.affiliation: Department of Biological Sciences, Macquarie University, New South Wales 2109, Australia. astow@rna.bio.mq.edu.au
authors.forename: Adam
authors.initials: A
authors.lastname: Stow
authors.forename: David
authors.initials: D
authors.lastname: Briscoe
authors.forename: Michael
authors.initials: M
authors.lastname: Gillings
authors.forename: Marita
authors.initials: M
authors.lastname: Holley
authors.forename: Shannon
authors.initials: S
authors.lastname: Smith
authors.forename: Remko
authors.initials: R
authors.lastname: Leys
authors.forename: Tish
authors.initials: T
authors.lastname: Silberbauer
authors.forename: Christine
authors.initials: C
authors.lastname: Turnbull
authors.forename: Andrew
authors.initials: A
authors.lastname: Beattie
mesh_terms: D000818:Animals; D000890:Anti-Infective Agents / Q000378:metabolism* / Q000494:pharmacology; D001516:Bees / Q000502:physiology*; D001522:Behavior, Animal / Q000502:physiology*; D005075:Biological Evolution; D008826:Microbial Sensitivity Tests; D012919:Social Behavior; D013211:Staphylococcus aureus / Q000187:drug effects
chemical_list: D000890:Anti-Infective Agents