Why Plants and Insects?

Nearly 75% of the world’s macroscopic biodiversity is tied up in the look between plants, herbivores, predators, and decomposers. In this context, the study of trophic interactions, involving plants, herbivores, and their predators or parasitoids represents a frontier in ecology, and this knowledge can be integrated in environmentally sound agricultural pest managements.

Present

I am currently working in the laboratory of Prof. Anurag Agrawal at Cornell University. My research is focusing on the evolution and mechanisms of plant-insect interactions belowground. I will use milkweed (Asclepias spp.) plants and their associated herbivore fauna, such as the monarch butterfly Danaus plexippus and the cerambycid beetles of the genus Tetraopes as model systems to deeply study the evolutionary ecology of above- and belowground direct and indirect defences in a natural system

Past studies and work

After studies in biology at the University of Neuchâtel with the specialization in ecology and systematic including botany, entomology, zoology and soil-plant biology, I joined the Laboratory of Evolutionary Entomology of Prof. Martine Rahier, for my diploma (master) work. The laboratory studies the interactions between plants, herbivorous insects and their natural enemies. Approaches varying from chemical ecology, behavioral ecology and evolutionary biology are used to capture the complexity of multitrophic interactions taking place between plants and higher trophic levels. The aim of the study was to investigate the effects of plant chemical defenses on the feeding and movement behaviour of alpine leaf beetle larvae belonging to the species Oreina elongata. Larvae were found to move back and forth from either plants providing chemical defenses (Adenostyles alliariae) such as alkaloids, and plants providing mechanical refuges such as the spines of thistles (Cirsium spinosissimum). For this purpose, I used combination of chemical and behavioural techniques to investigate larval alkaloid content, larval movement and predation rate in the field. This study first highlighted that larval behaviour can differently evolve compared to adult behaviour, and evolution is also driven by plant diversity [1].

After this successful experience, I started a graduate study program under the supervision of Prof. Ted Turlings where I had the possibility to be assistant at the entomology and soil biology practical courses, and where I could enjoy the stimulating atmosphere of the National Centre of Competence in research, Plant Survival at the University of Neuchâtel . My passion for insect-plant interaction studies was then very well married to the desire to acquire experience in the domain of biological control and sustainable agriculture, by starting a whole new project in the laboratory, and beginning to work on a newly introduced economically important pest in Europe : Diabrotica virgifera virgifera or Western Corn Rootworm (WCR) (see the spreading map). I started to develop methods to analyze behaviour and attractions of biological control agents of WCR, the entomopathogenic nematodes (EPNs) Heterorhabditis megidis. By constructing and developing a new belowground olfactometer, we were able to address the issue of plant attraction of EPNs to infested roots. Collaborations with the Max Planck Institute of Chemical Ecology in Jena , Germany helped me in the first attempt to discover a belowground chemical signal that was used by EPNs to locate their host. Surprisingly, WCR infected maize roots emit a volatile organic compound ((E)-b-caryophyllene) that was shown to be responsible for the attraction. After this laboratory demonstration, collaboration with CABI Bioscience in Delémont allowed me to prove our findings in the field. For this, I moved to Southern Hungary for a summer of field work, where I conclusively demonstrated that the signal that was found in the laboratory to be attractive was efficient in maize fields as well [2].

This first step of my thesis contributed to open an entire new field in ecology; i.e. the belowground tritrophic interactions, or the chemically mediated communication between plants, herbivores and their parasites. Plant mediated interactions between aboveground biota and belowground biota is a major issue nowadays. My discovery helped to enlarge the figure on what drives the structuring on natural communities, and how two previously separated compartments (i.e. aboveground and belowground) are connected. For this, I later combined the newly built belowground olfactometer and the already present aboveground olfactomer, which is used to study odor leaf emission and parasitic wasp behavior. The combination of the two olfactomers allowed me to asses that belowground herbivory can influence aboveground chemical communications between plants, caterpillars and parasitic wasps; and vice-versa that aboveground herbivory influences the belowground tritrophic interaction as described above [3].

I then built up on the recent knowledge acquired, and investigated the specificity of belowground tritrophic interactions. The three different trophic levels were investigated separately, using maize (Zea mays L.), cotton (Gossypium herbaceum L.) and cowpea (Vigna unguiculata L.); the beetles Diabrotica virgifera virgifera, Diabrotica balteata, Agriotes ustulatus (Elateridae) and the phytopathogenic nematodes Ditylenchus dipsaci (Tylenchida) as herbivores and the entomopathogenic nematodes Heterorhabditis  megidis, Heterorhabditis bacteriophora and Steinernema feltiae as parasites of herbivores. We found that belowground tritrophic interactions are variable on the level of plant volatile emissions, elicitation by herbivores, as well as behavior of nematodes [4].