Dr. Sybille Unsicker

   Department of Biochemistry
   Chemical Ecology in Poplar
 Phone:+49 (0)3641 57 1328Max Planck Institute for Chemical Ecology
 Fax:+49 (0)3641 57 1302Hans-Knöll-Straße 8
  emailD-07745 Jena

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PhD Thesis

Plant-Insect Interactions in grasslands along a gradient of plant species diversity
Friedrich-Schiller-Universität Jena, Biologisch-Pharmazeutische Fakultät
First Supervisor: Prof. Dr. W. Weisser (Institute of Ecology, FSU)

The fitness of primary consumers such as insect herbivores can be influenced by the diversity of plant species and other habitat variables that are associated directly or indirectly with plant species richness. The scope of this study was to study the fitness of Chorthippus parallelus females from 15 populations in the Franconian Forest and the Thuringian Slate Hills in relation to habitat variables such as plant species richness, plant community biomass, vegetation composition, Camargo’s eveness, and solar radiation. In addition, the abundance of C. parallelus grasshoppers in 11 study sites was investigated. Abundance increased with increasing plant species richness and increasing solar radiation in the sites. There was a significant relationship between grasshopper abundance and plant community structure. Female fecundity, measured as either the number of egg pods per female, or as the number of hatchlings in the next spring increased with an increase in plant species richness in the habitat of origin. C. parallelus occurred in three different color morphs (brown, green and striped) in the study area and females of the brown color morph laid significantly more egg pods than females in the green and striped morph. Possible explanations for the positive effects of plant diversity on the fitness of the generalist herbivore C. parallelus are discussed.