Antimicrobial strength increases with group size: Implications for social evolution

Christine Turnbull, Stephen Hoggard, Michael Gillings, Chris Palmer, Adam Stow, Doug Beattie, David Briscoe, Shannon Smith, Peter Wilson, Andrew Beattie

Research output: Contribution to journalArticleResearchpeer-review

Abstract

We hypothesize that aggregations of animals are likely to attract pathogenic micro-organisms and that this is especially the case for semisocial and eusocial insects where selection ultimately led to group sizes in the thousands or even millions, attracting the epithet 'superorganism'. Here, we analyse antimicrobial strength, per individual, in eight thrips species (Insecta: Thysanoptera) that present increasing innate group sizes and show that species with the largest group size (100-700) had the strongest antimicrobials, those with smaller groups (10-80) had lower antimicrobial activity, while solitary species showed none. Species with large innate group sizes showed strong antimicrobial activity while the semisocial species showed no activity until group size increased sufficiently to make activity detectable. The eusocial species behaved in a similar way, with detectable activity appearing once group size exceeded 120. These analyses show that antimicrobial strength is determined by innate group size. This suggests that the evolution of sociality that, by definition, increases group size, may have had particular requirements for defences against microbial pathogens. Thus, increase in group size, accompanied by increased antibiotic strength, may have been a critical factor determining the 'point of no return', early in the evolution of social insects, beyond which the evolution of social anatomical and morphological traits was irreversible. Our data suggest that traits that increase group size in general are accompanied by increased antimicrobial strength and that this was critical for transitions from solitary to social and eusocial organization.

LanguageEnglish
Pages249-252
Number of pages4
JournalBiology Letters
Volume7
Issue number2
DOIs
Publication statusPublished - 23 Apr 2011

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Thysanoptera
group size
Insects
anti-infective agents
Anti-Bacterial Agents
social insects
Insecta
antibiotics
microorganisms
insects
pathogens

Cite this

Turnbull, Christine ; Hoggard, Stephen ; Gillings, Michael ; Palmer, Chris ; Stow, Adam ; Beattie, Doug ; Briscoe, David ; Smith, Shannon ; Wilson, Peter ; Beattie, Andrew. / Antimicrobial strength increases with group size : Implications for social evolution. In: Biology Letters. 2011 ; Vol. 7, No. 2. pp. 249-252.
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Antimicrobial strength increases with group size : Implications for social evolution. / Turnbull, Christine; Hoggard, Stephen; Gillings, Michael; Palmer, Chris; Stow, Adam; Beattie, Doug; Briscoe, David; Smith, Shannon; Wilson, Peter; Beattie, Andrew.

In: Biology Letters, Vol. 7, No. 2, 23.04.2011, p. 249-252.

Research output: Contribution to journalArticleResearchpeer-review

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