Effects of plant diversity on invertebrate herbivory in experimental grassland
- 646 Downloads
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 Arrhenatherum grasslands. Plots differed in plant species richness (1, 2, 4, 8, 16, 60 species), number of functional groups (1, 2, 3, 4), functional group and species composition. 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 community 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 biodiversity-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 significant. 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 community level. The opposite pattern was found for herbivory in T. pratense phytometers. We conclude that (1) plant species richness is much less important than previously thought and (2) plant functional identity is a much better predictor of invertebrate herbivory in temperate grassland ecosystems.
KeywordsBiodiversity Ecosystem functioning Functional diversity Resource concentration Trophic interactions
We thank Mick J. Crawley for his generous encouragement and advice in statistical analysis. Winfried Voigt kindly provided data on invertebrate abundances, and the technical assistance of Sylvia Creutzburg and Nadine Mitschunas is greatly acknowledged. We thank Ernst-Detlef Schulze, Christian Körner, and two anonymous referees for many helpful comments on a previous version of this manuscript. This study was supported by the Deutsche Forschungsgemeinschaft through grants WE2618/4-1 and FOR 456 to WWW. CS was supported by the Studienstiftung des Deutschen Volkes. All experiments conducted comply with current German laws.
- Bahr C (2005) Effects of plant species diversity, identity and architectural density on the density of slugs in an experimental grassland. Diploma Thesis, University of Jena (in German)Google Scholar
- Burnham KP, Anderson DA (1998) Model selection and inference—a practical information—theoretic approach. Springer, Berlin Heidelberg New YorkGoogle Scholar
- Crawley MJ (2002) Statistical computing. An introduction to data analysis using S-Plus. Wiley, ChichesterGoogle Scholar
- Ellenberg H (1996) Vegetation Mitteleuropas mit den Alpen, 5 edn. Ulmer, StuttgartGoogle Scholar
- Gibson DJ (2002) Methods in comparative plant population ecology. Oxford University Press, OxfordGoogle Scholar
- Hassell MP (2000) The spatial and temporal dynamics of host-parasitoid interactions. Oxford University Press, OxfordGoogle Scholar
- Kowalski E (2005) Density patterns of invertebrate herbivores (Auchenorrhyncha and Heteroptera) along a diversity gradient in an experimental grassland. Diploma Thesis, University of Jena (in German)Google Scholar
- Kubitzky K (ed) (1993) The families and genera of vascular plants. Springer, Berlin Heidelberg New YorkGoogle Scholar
- Schmid B, Hector A, Huston MA, Inchausti P, Nijs I, Leadley PW, Tilman D (2002) The design and analysis of biodiversity experiments. In: Inchausti P (ed) Biodiversity and Ecosystem Functioning: Synthesis and Perspectives. Oxford University Press, Oxford, pp 61–75Google Scholar
- Spehn EM, Scherer-Lorenzen M, Schmid B, Hector A, Caldeira MC, Dimitrakopoulos PG, Finn JA, Jumpponen A, O’Donnovan G, Pereira JS, Schulze ED, Troumbis AY, Korner C (2002) The role of legumes as a component of biodiversity in a cross-European study of grassland biomass nitrogen. Oikos 98:205–218CrossRefGoogle Scholar
- Unsicker S, Renker C, Kahmen A, Spindler S, Buchmann N, Weisser WW (2005) Testing the efficiency of three 15N-labeled nitrogen compounds for indirect labeling of grasshoppers via plants in the field. Entomol Exp Appl 116 (in press)Google Scholar