Pharmacophagy in sawflies
Insects are called pharmacophagous, if they search for and take up compounds that are not used for nutritional benefits. Some diterpenoids of plants cause pharmacophagy in the Japanese sawfly species Athalia rosae ruficornis. It should be investigated whether native Athalia species are also pharmacophagous on diterpenoid-containing plants and whether this has an impact on their mating success. Bioassays and chemical analytical tools will be used.
Isolation of feeding-deterrent compounds of invasive plant species
On several invasive plant species, herbivorous insects are rather rare. The responsible deterrent compounds should be isolated by bioassays in combination with chromatographic methods. Native specialists or generalists of our breeding stocks may be used.
Detoxification of secondary plant compounds
Herbivorous generalists must have several ways to cope with plant toxins. We are interested in the detoxification of several plant secondary compounds. Putative enzymatic degradation pathways and degradation products should be investigated using gas chromatography and mass spectroscopy.
Enzymatic activities of plants and herbivorous insects
Some plant species contain metabolites that become biologically reactive only in combination with specific enzymes, for example after wounding. Such specific metabolite-enzyme-combinations should be investigated in selected plant species. Furthermore, we are interested whether herbivory may enhance these systems.
Effects of different experience on behavioural phenotypes of herbivourous insects
The experience with certain environmental conditions, for herbivores in particular with different host plant quality, can significantly influence the physiology and the overall behavioural phenotype of different developmental stages. In this project, herbivorous insects of different feeding types will be kept on different food qualities. In bioassays, the individuality of the behaviour of larvae and adults (and their offspring) will then be tested in different contexts.
Indirect influences of mycorrhiza on herbivores
By changing the nutrient and hormone composition as well as the defence chemistry of their hosts, mycorrhizal fungi could have an indirect effect on the performance of above-ground feeding herbivores. Using bioassays, you will investigate whether the mycorrhizal status of the roots can affect herbivores of different feeding types.
Impact of mycorrhiza on plant secondary metabolites
Due to the close coupling between myccorhizal fungi and their plants, we may expect chemical changes in the aboveground plant tissues. Using chemical analytical methods, the secondary metabolites (in leaf tissues as well as volatiles) will be investigated in colonised versus uncolonised plants.
Do herbivores have an impact on mycorrhiza?
By inducing plant defences and affecting the phytohormone concentrations, leaf-feeding herbivores may influence the colonisation of the roots by mycorrhizal fungi. You will study whether aboveground feeding of different herbivores has indeed an impact on the colonisation level of the roots.
Environmental impacts on the plant phloem composition
The phloem is a highly important transport system of the plant. Using aphids and stylectomy, the phloem can be collected and analysed. You will investigate, which compounds are present in the phloem and whether its composition is affected by external factors. You may also establish bioassays in which the effects of different phloem composition on the aphid performance can be investigated.