A cryptic host-parasitoid interaction reduces the impact of heatwaves on host populations

This is a dataset accompanying the preprint of the same title. The experiment investigated how parasitoid infection affects the heat tolerance of host populations, and how this interactive effect is modulated by the availability of nutrients (dietary yeast).

Abstract: Laboratory measures of thermal performances are widely used to predict the response of populations to climate change. However, such approaches rarely account for numerous stressors that organisms experience alongside a changing climate, such as interactions with consumers and food resources. Trophic interactions such as predation have been shown to stabilise prey populations during heatwaves. Parasitism not only greatly influences the demography as predation does, but also the physiological states of hosts. The extent to which parasitoid infection modifies the tolerance of host populations has not been addressed empirically. We hypothesised that parasitism would in contrast lower the heat tolerance of hosts, and that this negative effect would be more pronounced when nutrition was limited due to conflicts in resource allocation to different defensive processes. We, therefore, examined the independent and joint effects of an extreme temperature event, parasitism, and nutrition on the survival of three Drosophila hosts. Dietary yeast (a primary source of protein) had contrasting impacts on the ability of populations to withstand high temperatures and parasitoid infection. Past exposure to parasitoids stabilized host populations against heatwaves, regardless of their underlying susceptibility to parasitism. Particularly, parasitoid infection occurring on unsuitable hosts (no parasitoids successfully emerge from these hosts) also reduced the extent to which host abundances were decreased by heatwaves. Our results emphasize the context-dependency of heat tolerance which is crucial for predicting consumer-resource dynamics under climate change.