title: Social complexity and nesting habits are factors in the evolution of antimicrobial defences in wasps.
abstract: Microbial diseases are important selective agents in social insects and one major defense mechanism is the secretion of cuticular antimicrobial compounds. We hypothesized that given differences in group size, social complexity, and nest type the secretions of these antimicrobials will be under different selective pressures. To test this we extracted secretions from nine wasp species of varying social complexity and nesting habits and assayed their antimicrobial compounds against cultures of Staphylococcus aureus. These data were then combined with phylogenetic data to provide an evolutionary context. Social species showed significantly higher (18x) antimicrobial activity than solitary species and species with paper nests showed significantly higher (11x) antimicrobial activity than those which excavated burrows. Mud-nest species showed no antimicrobial activity. Solitary, burrow-provisioning wasps diverged at more basal nodes of the phylogenetic trees, while social wasps diverged from the most recent nodes. These data suggest that antimicrobial defences may have evolved in response to ground-dwelling pathogens but the most important variable leading to increased antimicrobial strength was increase in group size and social complexity.
authors.affiliation: Department of Biological Sciences, Macquarie University, North Ryde, Australia. stephen.hoggard@mq.edu.au
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Hoggard
authors.forename: Peter D
authors.initials: PD
authors.lastname: Wilson
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Beattie
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Stow
mesh_terms: D000818:Animals; D000890:Anti-Infective Agents / Q000276:immunology* / Q000494:pharmacology; D005075:Biological Evolution; D008826:Microbial Sensitivity Tests; D009425:Nesting Behavior / Q000187:drug effects / Q000502:physiology*; D010802:Phylogeny; D012919:Social Behavior; D013211:Staphylococcus aureus / Q000187:drug effects; D014863:Wasps / Q000187:drug effects / Q000276:immunology* / Q000382:microbiology*
chemical_list: D000890:Anti-Infective Agents