@article{1ff0d1fde8c54b49a2e07eb9e91aa9b6,
title = "External immunity in ant societies: Sociality and colony size do not predict investment in antimicrobials",
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.",
author = "Penick, {Clint A.} and Omar Halawani and Bria Pearson and Stephanie Mathews and L{\'o}pez-Uribe, {Margarita M.} and Dunn, {Robert R.} and Smith, {Adrian A.}",
note = "Funding Information: Ethics. Research on arthropods does not require ethical approval, but we took efforts to limit stress to individuals and populations whenever possible. Data accessibility. All data are included in the online electronic supplementary material. Authors{\textquoteright} contributions. C.A.P., A.A.S., O.H., M.M.L.-U. and R.R.D. conceived and designed the study. C.A.P., A.A.S., O.H., B.P. and S.M. conducted field sampling and laboratory tests. C.A.P. and M.M.L.-U. conducted statistical analyses. C.A.P., A.A.S., M.M.L.-U. and R.R.D. drafted the manuscript, and all authors gave final approval for publication. Competing interests. We have no financial or non-financial competing interests to declare. Funding. Funding for this study was provided by a Triangle Center for Evolutionary Medicine (TriCEM) grant awarded to C.A.P., M.M.L.-U., S.M. and A.A.S.; an NC State University undergraduate research fellowship awarded to O.H. and B.P.; and a National Science Foundation (NSF) Postdoctoral Fellowship (1523817 to M.M.L.-U.). R.R.D. and C.A.P. were both supported by National Science Foundation grants (0953390 and 1319293) awarded to R.R.D.. Acknowledgements. This work emerged from an undergraduate course on Public Health (BIO 495, Fall 2015) at NC State University with participation from Kiran Gangwani, Michael Jones, Ted Bledsoe, and Aya Yanagawa. Publisher Copyright: {\textcopyright} 2018 The Authors.",
year = "2018",
month = feb,
doi = "10.1098/rsos.171332",
language = "English (US)",
volume = "5",
journal = "Royal Society Open Science",
issn = "2054-5703",
publisher = "The Royal Society",
number = "2",
}