Diet and thermal limits: eating for survival and fertility

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Climate change increases the frequency of extreme weather events. Heatwaves can kill organisms, but may also increase extinction risk by harming fertility. Sperm are thought to be especially sensitive to heat, and male insects often become infertile at lower-than-fatal temperatures. But can organisms do anything to buffer against temperature extremes? Recent discoveries show that remarkably, the fruit fly Drosophila melanogaster, changes its diet to buffer against heat and cold. It switches its food preferences in response to temperature, to obtain dietary lipids that allow it to better survive. Specifically, eating plant-derived lipids helps it survive the cold, while eating yeast-derived lipids helps it survive the heat. However, we do not know whether this adaptation is also present in other species that experience different climates, nor whether dietary changes improve reproductive performance, as well as survival, under temperature stress.Objectives:The overall aim is to test whether different species of fruit flies, originating from a range of natural climates, use diet switches to survive and reproduce under temperature extremes. The specific objectives are:1) To test the hypothesis that temperature-mediated diet switches are more prevalent in species that experience bigger seasonal temperature ranges.2) To test whether dietary lipids alter the reproductive performance of males and females under temperature extremes.Novelty and Timeliness:Knowledge of how organisms mitigate against extreme temperatures is vital if we are to predict how biodiversity will respond to climate change. The role of diet relatively unexplored, but has the potential to act as a prophylactic against temperature extremes. This project will establish whether diet switching is a widespread temperature coping mechanism among a genus of insects, covering a wide climatic range. The project will also explore whether fertilisation success - a key factor in species' persistence and in sexual selection - is part of the equation.