PLANT-ANIMAL INTERACTIONS Christoph Scherber Æ Peter N. Mwangi Vicky M. Temperton Æ Christiane Roscher Jens Schumacher Æ Bernhard Schmid Wolfgang W. Weisser Effects of plant diversity on invertebrate herbivory in experimental grassland Received: 23 December 2004 / Accepted: 14 September 2005 / Published online: 18 October 2005 Ó Springer-Verlag 2005 Abstract The rate at which a plant species is attacked by invertebrate herbivores has been hypothesized to depend on plant species richness, yet empirical evidence is scarce. Current theory predicts higher herbivore damage in monocultures than in species-rich mixtures. We quantified herbivore damage by insects and molluscs to plants in experimental plots established in 2002 from a species pool of 60 species of Central European Arrhen- atherum grasslands. Plots differed in plant species rich- ness (1, 2, 4, 8, 16, 60 species), number of functional groups (1, 2, 3, 4), functional group and species com- position. We estimated herbivore damage by insects and molluscs at the level of transplanted plant individuals (‘‘phytometer’’ species Plantago lanceolata, Trifolium pratense, Rumex acetosa) and of the entire plant com- munity during 2003 and 2004. In contrast to previous studies, our design allows specific predictions about the relative contributions of functional diversity, plant functional identity, and species richness in relation to herbivory. Additionally, the phytometer approach is new to biodiversity-herbivory studies, allowing estimates of species-specific herbivory rates within the larger bio- diversity-ecosystem functioning context. Herbivory in phytometers and experimental communities tended to increase with plant species richness and the number of plant functional groups, but the effects were rarely sig- nificant. Herbivory in phytometers was in some cases positively correlated with community biomass or leaf area index. The most important factor influencing invertebrate herbivory was the presence of particular plant functional groups. Legume (grass) presence strongly increased (decreased) herbivory at the com- munity level. The opposite pattern was found for her- bivory in T. pratense phytometers. We conclude that (1) plant species richness is much less important than pre- viously thought and (2) plant functional identity is a much better predictor of invertebrate herbivory in tem- perate grassland ecosystems. Keywords Biodiversity Æ Ecosystem functioning Æ Functional diversity Æ Resource concentration Æ Trophic interactions Flowering plants comprise more than 260,000 species worldwide (Kubitzky 1993) and constitute a major component of all biomass in terrestrial ecosystems. About 400,000 known species of phytophagous insects feed on them, with about 90% exhibiting high degrees of host specialization (Bernays and Graham 1988). While there is a wealth of studies on the relationship between plant diversity and diversity of herbivorous insects (e.g. Haddad et al. 2001; Koricheva et al. 2000; Mulder et al. 1999; Siemann et al. 1998), surprisingly little is known about the relationship between plant diversity and the damage caused by herbivorous insects, i.e. the amount of herbivory itself, both at the level of the entire plant community and of individual plants. Agricultural experiments suggest that because of larger densities of specialist herbivores, greater herbivore damage at the individual level should occur in plant monocultures than in plant mixtures (Andow 1991; Finch and Collier 2000). The ‘resource concentration’ and the ‘enemies’ Communicated by Christian Koerner C. Scherber (&) Æ C. Roscher Æ J. Schumacher Æ W. W. Weisser Institute of Ecology, University of Jena, Dornburger Str. 159, 07743 Jena, Germany E-mail: Christoph.Scherber@web.de Tel.: +49-3641-949406 Fax: +49-3641-949402 V. M. Temperton Æ J. Schumacher Max Planck Institut fu¨r Biogeochemie, PO Box 10 01 64, 07701 Jena, Germany P. N. Mwangi Æ B. Schmid Institute of Environmental Sciences, University of Zurich, Winterthurerstr. 190, 8057 Zurich, Switzerland Oecologia (2006) 147: 489–500 DOI 10.1007/s00442-005-0281-3