Interactions between a leaf-galling wasp and its invasive hawkweed hosts

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Holmes, Gregory
University of Lethbridge. Faculty of Arts and Science
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Lethbridge, Alta : University of Lethbridge, Dept. of Biological Sciences
This thesis aims to explore the interactions between a potential biocontrol agent, the gall-wasp Aulacidea pilosellae, and its invasive Pilosella hawkweed hosts. I discovered that increased nitrogen availability improves P. officinarum vegetative growth, while also interacting with A. pilosellae to reduce vegetative growth, as the plants cannot compensate for this herbivory. I did not detect any nitrogen effects on wasp performance. I also explored how the host species utilized for galling affects wasp performance through two generations by measuring maternal effects. These only influenced offspring performance when the mother had utilized P. caespitosa, but not P. glomerata. I discovered that P. caespitosa is also the better offspring host, producing significantly larger galls and heavier larvae compared to P. glomerata. These results may help identify, 1) if underlying site fertility may be associated with increases in agent performance and/or impact on the target weed, and 2) to indicate the appropriate Pilosella species to target in a biocontrol programme.
hawkweeds , gall wasp , biocontrol , nitrogen , maternal effects , insect-plant interactions