External immunity in ant societies: Sociality and colony size do not predict investment in antimicrobials

Clint Penick, Omar Halawani, Bria Pearson, Stephanie Mathews, Margarita M. López-Uribe, Robert R. Dunn, Adrian A. Smith

Research output: Contribution to journalArticle

5 Scopus citations

Abstract

Social insects live in dense groups with a high probability of disease transmission and have therefore faced strong pressures to develop defences against pathogens. For this reason, social insects have been hypothesized to invest in antimicrobial secretions as a mechanism of external immunity to prevent the spread of disease. However, empirical studies linking the evolution of sociality with increased investment in antimicrobials have been relatively few. Here we quantify the strength of antimicrobial secretions among 20 ant species that cover a broad spectrum of ant diversity and colony sizes. We extracted external compounds from ant workers to test whether they inhibited the growth of the bacterium Staphylococcus epidermidis. Because all ant species are highly social, we predicted that all species would exhibit some antimicrobial activity and that species that form the largest colonies would exhibit the strongest antimicrobial response. Our comparative approach revealed that strong surface antimicrobials are common to particular ant clades, but 40% of species exhibited no antimicrobial activity at all. We also found no correlation between antimicrobial activity and colony size. Rather than relying on antimicrobial secretions as external immunity to control pathogen spread, many ant species have probably developed alternative strategies to defend against disease pressure.

Original languageEnglish (US)
Article number171332
JournalRoyal Society Open Science
Volume5
Issue number2
DOIs
StatePublished - Feb 2018

Keywords

  • Antibiotics
  • Antimicrobial secretions
  • Ants
  • Entomopathogens
  • Social immunity
  • Social insects

ASJC Scopus subject areas

  • General

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    Penick, C., Halawani, O., Pearson, B., Mathews, S., López-Uribe, M. M., Dunn, R. R., & Smith, A. A. (2018). External immunity in ant societies: Sociality and colony size do not predict investment in antimicrobials. Royal Society Open Science, 5(2), [171332]. https://doi.org/10.1098/rsos.171332