Endosymbionts and honey bee colony losses?

Endosymbionts

and

honey

bee

colony

losses?

Alexandre

Aebi

and

Peter

Neumann

1_{AgroscopeReckenholz-Ta¨nikon,ResearchStationART,Reckenholzstrasse191,CH-8046Zu¨rich,Switzerland}

2_{SwissBeeResearchCentre,AgroscopeLiebefeld-Posieux,ResearchStationALP,Schwarzenburgstrasse161,CH-3003Bern,}

Switzerland

3_{DepartmentofZoologyandEntomology,RhodesUniversity,Grahamstown6140,SouthAfrica}

Honeybees,Apismellifera,areessentialpollinatorsforthe maintenance of natural biodiversity and agriculture[1]. Colony losses witnessed throughout theNorthern hemi-sphere are therefore worrying[2], especially becauseno singledriverhasyetemergedasthedefinitivecause[3]. Interactions between viruses, ectoparasitic mites and microsporidianendoparasites aremostlikelykey factors [3–5],buttheunderlyingmechanismsarenotwell under-stood. Although it is known that maternally-inherited, facultative bacterial endosymbionts such as Wolbachia or Rickettsia can significantly interfere with viral and fungalinfections ofarthropods[6],theyhaveso farbeen neglectedinthisregard.Hereweproposetoevaluatethe potentialroleofsuchendosymbiontsforcolonylosses.

Endosymbionts are widespread [7] inarthropods and transmitted vertically [8], but can only spread in host populationswheninfected femaleshaveahigherfitness, e.g.via providingprotection againstvirusesorfungi[6]. Forexample,Wolbachiacanprotectthehostagainst sev-eralvectoredRNAviruses[9]andcanberegardedaspart of host immunity [6]. However, endosymbionts such as Spiroplasma andHamiltonella canalso bebeneficial for theirhost’svectorialcapacity,e.g.inthewhiteflyBemisia tabaci–Tomatoyellowleafcurlvirussystem,Hamiltonella protectsviralparticlesinthevector[6,10].

Toshedlightonthepotentialinfluenceofendosymbionts on losses, we heresuggest an investigationof symbiont-mediated hostprotection against viruses transmitted by parasitic mites and/or associated with microsporidians (e.g. Nosema ceranae) [5], which could contribute to the toleranceof honey bee populations, e.g. against the mite Varroadestructor[11].Moreover,endosymbiontscarriedby parasitic mites might favour virus transmission to and virulenceinhoneybees,whichcouldexplainregional differ-encesinthe impactof mites[11].Acombinationof meta-genomicsandlaboratoryexperimentsappearssuitableto compare the bacterial and viral communities associated with honey bees andtheir parasites inhost populations

withorwithoutelevatedlosses[2].Inconclusion,itseemsas ifendosymbiontsplayaroleinhoneybeepathology[12]and shouldthereforebeinvestigatedasapotentialkeytoour understandingofmajorcolonylosses.

Acknowledgements

Wethank VincentDietemann,Einat Zchori-Fein,DanieleDaffonchio, AmeurCherifandRenateZindelforstimulatingdiscussionsandtheFP7 projectsSTEPandBEEDOC(P.N.),theCOSTActionsFA0803COLOSS (P.N.andA.A.)andFA0701(A.A.)forfinancialsupport.

References

1Klein, A.M. et al. (2007) Importance of pollinators in changing landscapesforworldcrops.ProcR.Soc.Lond.B.274,303–313 2Neumann,P.andCarreck,C.(2010)Honeybeecolonylosses:aglobal

perspective.J.Apic.Res.49,1–6

3 Potts,S.G.etal.(2010)Globalpollinatordeclines:driversandimpacts. TrendsEcol.Evol.25,345–353

4 Yang,X.andCox-Foster,D.L.(2005)Impactofanectoparasiteonthe immunity and pathology of an invertebrate: Evidence for host immunosuppressionand viral amplification. Proc. Natl. Acad. Sci. U.S.A.102,7470–7475

5 Bailey, L. et al. (1983) Association of virus with two protozoal pathogensofthehoneybee.Ann.Appl.Biol.103,13–20

6 Zindel,R.etal.(2011)Arthropodsymbioses,aneglectedparameterin pest-anddisease-controlprogrammes.J.Appl.Ecol.48,864–872 7 Hilgenboeker,K.etal.(2008)Howmanyspeciesare infectedwith

Wolbachia?.Astatisticalanalysisoncurrentdata.FEMSMicrobiol. Lett.281,215–220

8 O’Neill, S.L. et al. (1997) Influential passengers: Inherited microorganismsandarthropodreproduction,OxfordUniversityPress 9 Teixeira,L.etal.(2008)ThebacterialsymbiontWolbachiainduces resistancetoRNAviralinfectionsinDrosophilamelanogaster.PLoS Biol.6, e1000002

10Gottlieb,Y.etal.(2010)ThetransmissionefficiencyofTomatoYellow Leaf CurlVirusby thewhitefly Bemisia tabaciis correlatedwith thepresenceofaspecific symbioticbacteriumspecies.J.Virol.84, 9310–9317

11Rosenkranz,P.etal.(2010)ThebiologyandcontrolofVarroadestructor. J.Inv.Pathol.103,96–119

12Evans, J.D. and Armstrong, T.N. (2006) Antagonistic interactions betweenhoneybeebacterialsymbiontsandimplicationsfordisease. BMCEcol.6,DOI:10.1186/1472-6785-6-4

Correspondingauthor:Neumann,P. (peter.neumann@alp.admin.ch).

Published in Trends in Ecology and Evolution 26, issue 10, 494, 2011 which should be used for any reference to this work