This project investigates how short bursts of extreme heat, like the heatwaves that are becoming more common with climate change, might change the relationship between fruit flies and the tiny wasps that parasitise them. Many insects can only function within a narrow temperature range, so sudden increases can affect how they survive, develop, and interact with other species.

Fruit flies and their parasitic wasps provide an ideal system for studying these changes. The wasp injects its eggs into a fruit fly larva, and the developing wasp eventually kills the host. Fruit flies can defend themselves by using their immune system to recognise the wasp egg and form a capsule around it. The wasps, in turn, have evolved ways to hide from or disable these defences, creating a natural evolutionary “arms race.”

This project explores how heat stress disrupts this back-and-forth, by exposing the fruit fly (Drosophila melanogaster) and the wasp (Asobara tabida) to short, intense heat shocks and then measuring how this affects their parasitism success and host resistance. The thermal limits of both these species are also tested across different life stages to see which stages are most vulnerable. Together, these results provide insight into how their interaction may shift under rapid changes in temperature.

This research helps build understanding of how climate change could disrupt the natural balance between fruit flies and the parasitic wasps that help control their populations. If extreme heat weakens the wasps more than the flies, parasitism rates may drop, allowing fruit fly numbers to rise. As fruit flies are major agricultural pests, this could lead to more crop damage, greater reliance on chemical pesticides, and higher economic and environmental costs.

By identifying which species or life stages are most vulnerable to heat stress, this work provides early warning signs for when biological control systems might begin to fail. It also supports predictions about whether current pest-management strategies will remain effective as the climate warms.

Without a clear understanding of these changes, natural pest-control partners that many crops depend on may be lost. This work supports farmers, ecosystems, and future climate-resilient agriculture by helping plan for a world where heatwaves are more frequent and more intense.

| Te Whare Wānanga o Waitaha – University of Canterbury |