Oecologia (2009) 160:267–277 DOI 10.1007/s00442-009-1294-0 P L A N T - A N I M A L I N T E R A C T I O N S - O R I G I N A L P A P E R SpeciWc bottom–up eVects of arbuscular mycorrhizal fungi across a plant–herbivore–parasitoid system Stefan Hempel · Claudia Stein · Sybille B. Unsicker · Carsten Renker · Harald Auge · Wolfgang W. Weisser · François Buscot Received: 18 February 2008 / Accepted: 19 January 2009 / Published online: 14 February 2009 © Springer-Verlag 2009 Abstract The majority of plants are involved in symbio- ses with arbuscular mycorrhizal fungi (AMF), and these associations are known to have a strong inXuence on the performance of both plants and insect herbivores. Little is known about the impact of AMF on complex trophic chains, although such eVects are conceivable. In a green- house study we examined the eVects of two AMF species, Glomus intraradices and G. mosseae on trophic interac- tions between the grass Phleum pratense, the aphid Rhopalosiphum padi, and the parasitic wasp Aphidius rhop- alosiphi. Inoculation with AMF in our study system gener- ally enhanced plant biomass (+5.2%) and decreased aphid population growth (¡47%), but there were no fungal spe- cies-speciWc eVects. When plants were infested with G. intraradices, the rate of parasitism in aphids increased by 140% relative to the G. mosseae and control treatment. Communicated by Hormoz BassiriRad. S. Hempel (&) · C. Renker · F. Buscot Department of Soil Ecology, Helmholtz Centre for Environmental Research–UFZ, Theodor-Lieser-Straße 4, 06120 Halle, Germany e-mail: hempel.stefan@gmail.com C. Renker e-mail: carsten.renker@stadt.mainz.de F. Buscot e-mail: francois.buscot@ufz.de C. Stein · H. Auge Department of Community Ecology, Helmholtz Centre for Environmental Research–UFZ, Theodor-Lieser-Straße 4, 06120 Halle, Germany C. Stein e-mail: claudia.stein@ufz.de H. Auge e-mail: harald.auge@ufz.de When plants were associated with AMF, the developmental time of the parasitoids decreased by 4.3% and weight at eclosion increased by 23.8%. There were no clear eVects of AMF on the concentration of nitrogen and phosphorus in plant foliage. Our study demonstrates that the eVects of AMF go beyond a simple amelioration of the plants’ nutri- tional status and involve rather more complex species-spe- ciWc cascading eVects of AMF in the food chain that have a strong impact not only on the performance of plants but also on higher trophic levels, such as herbivores and para- sitoids. Keywords Aphidius rhopalosiphi · Insect herbivory · Multitrophic interactions · Parasitoid performance · Rhopalosiphum padi S. B. Unsicker Department of Biochemistry, Max Planck Institute for Chemical Ecology, Hans-Knöll-Straße 8, 07745 Jena, Germany e-mail: sunsicker@ice.mpg.de W. W. Weisser Institute for Ecology, Friedrich-Schiller-University Jena, Dornburger Straße 159, 07743 Jena, Germany e-mail: wolfgang.weisser@uni-jena.de Present Address: C. Renker Naturhistorisches Museum Mainz, Reichklarastraße 10, 55116 Mainz, Germany 123