1 ANTIMICROBIALS AND THE EVOLUTION OF EUSOCIALITY Andrew Beattie Christine Turnbull Department of Biological Sciences Macquarie University Sydney, Australia

2 The major social insects Ants (© Ron Oldfield) Social wasps ©Micropolitan.org Social bees ©2008 Peter O Termites

3 Criteria for Eusociality 1. Cooperative brood care 2. Reproductive division of labour; castes 3. Overlap between at least two generations; offspring assist parents 4. Is there another one?

4 THIS TALK Bull ants Bees Wasps Thrips (Bioprospecting)

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6 Bull Ants have two defences against antimicrobial attack 1.EXTERNAL Paired metapleural glands Strong antiseptic

7 Extracting antimicrobial metapleural secretions

8 Metapleural secretion activity against microorganisms Yeasts (fungi):strong Gram + bacteria:mixed Gram –ve: strong

9 Bull Ant Antimicrobial defences: 2 – Internal Reverse-phase HPLC A: control haemolymph B; challenge haemolymph F1, F2 inducible O- glycosylated proline-rich antibacterial peptides ‘Formaecins’ Non-glycosylated synthetic isoform had very reduced activity J. Biol. Chem. 273: (1998) Jim Mackintosh F1,F2 active against inoculum

10 Summary: Bull Ant Antimicrobials:: external and internal Two-tier antimicrobial defence system: 1.External antiseptics from metapleural gland 2.Internal immune system with inducible peptides But all ant species highly eusocial – what about species at earlier stages of sociality?

11 Hypothesis: Antimicrobials increase in strength with group size and level of social organisation EXPERIMENT: To compare social insects that are solitary, semi-social and eusocial Australian bees: Amegilla, Exoneura, Exoneurella, Trigona Hypothesis

12 Within-colony density social Within-colony genetic diversity solitary Disease Threat Semi-social

13 Sampling E. robusta– mountain ash forests

14 Sampling E. nigrescens- fire induced heathland

15 Antimicrobial Activity New Bioassay: Opposing gradients of antimicrobial strength and microbial inoculum Growth of golden staph completely inhibited

16 Antimicrobial Strength: Minimum Inhibitory Concentrations Status Species MIC (50) MIC(100) Solitary A.cingulata Solitary A. bombif Semi- E. robusta Semi- E. nigresc Social Ex. Trident Social T. carbon

17 ANTIMICROBIAL STRENGTH IN BEES density genetic diversity solitary semi-social eusocial antimicrobial POINT OF NO RETURN?

18 Conclusions: Group size and within-colony relatedness inceases with increasing sociality. (Fungal loads were greatest in solitary species) Antimicrobials strong in social bees, weakest in solitaries Major increase in antimicrobial strength with first signs of sociality

19 Antimicrobial Activity of Wasps species.

20 Wasp Summary: Social species showed significantly higher (18x) antimicrobial activity than solitary species The most important variable leading to increased antimicrobial strength was increase in group size and social complexity.

21 Antimicrobials in Thrips: solitary and social

22 LB Control Staph Control Social Thrips Wasp extract effective at 1/32 nd of a wasp equivalent Social thrip extract effective at 50 thrip equivalents Social Wasps Solitary thrip extract no effect at 180 thrip equivalents Lb + extract solitary

23 Concentration–growth response curves showing activity of extracts from eight thrips species against S. aureus. Turnbull C et al. Biol. Lett. doi: /rsbl ©2010 by The Royal Society Soc eusoc Semi -soc

24 Next phase the only known eusocial beetle: Astroplatypus incompertus

25 Antimicrobial traits and the evolution of sociality/eusociality (i) Social evolution means increasing group size and colony complexity; manifestly increasing the need for antimicrobial defences. Thus, the traits that enabled nascent colonies to combat microbial pathogens have been fundamental to social evolution in thrips and should be included with the other essentials.

26 Antimicrobial traits and the evolution of sociality (ii) Was there a role for microbial pathogens in social evolution? 1) The first response appears to have been an increase in the strength of antimicrobial compounds. 2) Limits to this response, e.g. resource limitation or self- antibiosis might require an increase the number of individuals producing antimicrobials. This scenario embeds a role for microbial pathogens in the social evolution of thrips. What about all the other social insect groups?

27 Bioprospecting using ecological and evolutionary hypotheses Already big-time (NIH) ( Evolutionary and Ecological Applications J. Biological Engineering J. Biomimicry Hypothesis-Driven Bioprospecting

28 For pharmaceuticals in general (Henkel et al. 1999,Angew. Chem. Int. Ed. 38:643)

29 Sources of Drugs (from Newman et al Journal of Natural Products) All NEW COMPOUNDS 28% from natural product or derivative 24% based on natural product or mimic 52% ALL ANTICANCER DRUGS 40% from natural product or derivative 21% based on natural product or mimic 61%

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31 THANKS TO ADAM STOW CHRISTINE TURNBULL DAVID BRISCOE MICHAEL GILLINGS JIM MACINTOSH SHANNON SMITH HELEN DOCHERTY RUTH BURTON DUNCAN VEAL PAUL DUCKETT KEIRA BEATTIE DOUG BEATTIE SAM HUSSEY SIOBHAN DENNISION PETER WILSON DAVID NIPPERESS MICHAEL SCHWARTZ STEPHEN HOGGARD CHRIS PALMER TOM CHAPMAN HOLLY CARAVAN