Abstract/Summary

A key threat of projected climate change to ecosystems is disruption to species interactions. Disruptions are predicted to occur when responses to temperature differ among interacting species, particularly when they differ in their respective thermal optima and degree of thermal specialisation. In this thesis I parameterise the Rosenzweig-MacArthur model with temperature dependent variables using published data to investigate how differences in thermal adaptation affect interactions between crop pests and their parasitoids in a changing climate. I determine the relative importance of temperature-dependence in the model variables, and I introduce a new model parameter to explore the importance of asynchrony in development rate between species. I then explore temperature variability in these models to explore the impacts of diurnal and seasonal variation on pest-parastoid dynamics and predict outcomes under a full range of climate model projections for alternative climate change scenarios. Finally, I experimentally tested some of the model assumptions under laboratory conditions. In principle, when pest and parasitoid share the same thermal optima across traits, pest abundance is expected to increase in a warmer climate primarily due to an increase in the frequency of population peaks. This effect is strongest if the pest interacts with a relatively cool-adapted parasitoid but is mitigated, and even reversed, with a relatively warm-adapted parasitoid. Thermal specialist parasitoids can be more effective than thermal generalists but quickly lose efficacy in a changing or more variable climate. When I incorporated different sources of temperature variability into my models, pest abundance was predicted to decrease with future climate change, indicating that species likely operate much closer to their thermal optima than might be assumed. Coupling temperature variability with scenarios of differences in thermal adaptation between pest and parasitoid yielded even greater uncertainty in model outputs.