Stine-Marie Simensen

Supervisor: Francis Gilbert

Research Interests

My research is centred on plant-insect interactions dealing predominantly with plant defence and insect herbivory. Across the plant kingdom there is a great variety of strategies to repel and protect the plant from herbivores. These defences may involve chemical and mechanical defences acting to resist herbivory, as well as mechanisms of tolerance. One of the key plant defences against insect herbivores is their diverse array of secondary metabolites. There are three main groups of chemical substances implicated in defence; phenolics, terpenoids, and nitrogen compounds such as cardenolides.

In my research I am focusing on the Sinai Milkweed, Gomphocarpus sinaicus, and its insect herbivores, specifically the weevil Paramecops sinaitus. The Sinai milkweed is a highly toxic perennial shrub, renowned for exuding latex containing cardenolides upon damage. Cardenolides act by disrupting the sodium and potassium flux in cells and are thereby toxic to most animals, yet it supports at least five herbivore species. The insects feeding on the Sinai milkweed either actively avoid or consume and sequester the defences of the plant.

Using a combination of analytical chemistry and ecological data I will investigate what the determinants of cardenolide content is, if it’s constituent or induced, and whether there is individual variation. Further, I will investigate the effects of variation in cardenolide content on the distribution, feeding, and mating behaviour on several of the insect herbivores.