Performance of a leaf beetle in a multitrophic context
Independent thesis Advanced level (degree of Master (Two Years)), 40 credits / 60 HE creditsStudent thesis
The aim of my thesis was to assess the relative importance of bottom-up and top-down forces for a plant-herbivore system in a natural multitrophic context. The system consisted of the tall herb Meadowsweet, Filipendula ulmaria (Rosaceae), and the Strawberry leaf beetle Galerucella tenella (Coleoptera: Chrysomelidae). I set up a field experiment with four clones of each of 16 genotypes varying in food quality. The four clones of each genet were assigned to one of four G. tenella egg density treatments (10, 20, 40 or 80 eggs). I hypothesized that (1) larval performance increases with plant edibility; (2) larval performance increases at higher larval densities (3) the parasitation rate by the hymenopteran parasitoid Asecodes parviclava increases with increasing larval density and decreasing food quality. The results showed significant relationships between larval density treatment and G. tenella survival (negative), pupal weight (positive), proportion of parasitoids (negative) and generalist predators (positive; for both functional groups “web-forming spiders” and “others”), and plant chewers. Parasitation rate was unaffected by treatments. Otherwise, complex interaction effects dominated and support for my hypotheses was low. Analysis of phenolic compounds, using liquid chromatography-mass spectrometry (LC-MS), showed positive correlations between plant damage and quercetin, and plant quality and catechin. Taken together my study indicates that larval performance is affected by both plant quality and larval density. It is likely that herbivore damage induces release of volatile organic compounds (HI-VOCs), attracting other arthropods. The strength and direction of those interactions will depend upon the composition of the local arthropod community.
Place, publisher, year, edition, pages
2015. , 26 p.
Plant-herbivore interactions, parasitoids, generalist predators, multitrophic interactions, plant chemistry
IdentifiersURN: urn:nbn:se:umu:diva-114081OAI: oai:DiVA.org:umu-114081DiVA: diva2:893535
2015-06-05, 11:30 (English)
Ericson, LarsAlbrectsen, Benedicte