Organisms face a constant risk of attack from parasites. While classic immunology has revealed numerous physiological and molecular mechanisms that underpin host immunity, the recently developed field of ecological immunology has attempted to understand the ecological and evolutionary causes that explain the diversity of such immune mechanisms. However, progress in the field has been hampered by the complex relationship between immunity and fitness as well as the methodological limitations of our experiments. There is an urgent need for eco-immunological studies that combine life history theory with experimentally tractable but ecologically realistic host and pathogen models. In this thesis, I tackle three novel aspects of host defence against parasites in an established model for insect immunity, the fruit fly Drosophila melanogaster, with the entomopathogenic fungus Metarhizium robertsii, one of the most successful natural insect pathogens. In particular, I show in Chapter 2 that an immune and stress response gene, Turandot M, provides specific immunity against sexually transmitted fungal infections; but, this protective effect comes at a cost to life history in the absence of infection. In Chapter 3, I show that when exposed to the fungal pathogen, the fruit fly alters its temperature preference by seeking out cooler temperatures, which results in a dramatic shift in its life history strategy while simultaneously enhancing antifungal resistance, though not tolerance. Finally, I demonstrate in Chapter 4 that exposure to fungal parasites induces fitness-associated maternal effects on offspring meiotic recombination and life history, both of which have the potential to accelerate adaptive evolution. Taken together, these results demonstrate the benefits of integrating life history theory in eco-immunological research. They show that life history responses are an integral component of host defence against parasites, and that Drosophila-Metarhizium is a promising model system for ecological immunology.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:648938 |
| Date | January 2014 |
| Creators | Zhong, Weihao |
| Contributors | Priest, Nicholas |
| Publisher | University of Bath |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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