The evolution of lifespan and ageing in response to dietary macronutrients in male and female decorated crickets

Dietary macronutrients regulate lifespan and ageing, yet little is known about their evolutionary effects. Here, we examine the evolutionary response of these traits in decorated crickets (Gryllodes sigillatus) maintained on diets varying in caloric content and protein-to-carbohydrate ratio. After 37 generations, each population was split: half remained on the evolution diet and half switched to a standardized diet. Crickets lived longer and aged slower when evolving on high-calorie (both sexes) and carbohydrate-biased (females only) diets and had lower baseline mortality on high-calorie (females only) diets. However, on the standardized diet, crickets lived longer when evolving on high-calorie diets (both sexes), aged slower on high-calorie (females only) and carbohydrate-biased (both sexes) diets, and had lower baseline mortality on high-calorie (males only) and protein-biased (both sexes) diets. Lifespan was longer and baseline mortality lower when provided the evolution versus the standardized diet but ageing rate was comparable. Moreover, lifespan was longer, ageing slower (females only) and baseline mortality lower (males only) compared to our evolved baseline suggesting varying degrees of dietary adaptation. Collectively, we show dietary components influence the evolution of lifespan and ageing in different ways and highlight the value of combining experimental evolution with nutritional geometry.