Macronutrients and micronutrients drive trade-offs between male pre- and postmating sexual traits

Nutrition fundamentally affects life span and reproduction, and identifying how nutrient intakes are linked to the expression of these life-history traits can advance understanding of the mechanisms underlying life-history trade-offs. Males are thought to face trade-offs between the allocation of resources to premating secondary sexual traits for gaining access to females and allocation to postmating traits such as ejaculate quality that affects their fertility. We used the Geometric Framework for nutrition to examine the effects of macronutrient and micronutrient consumption on life span and the expression of pre- and postmating sexual traits in male field crickets Teleogryllus oceanicus. We found that life span was maximized on diets with a low protein-to-carbohydrate (P:C) ratio, whereas premating sexual traits (courtship song and cuticular hydrocarbons) were maximized on high P:C ratios. In contrast, sperm viability, a postmating trait, was lowest on high-P:C-ratio diets. Higher consumption of micronutrients (minerals and vitamins) was associated with decreased life span and lower relative abundances of longer chained CHCs, but improved the performance of sperm viability and courtship song. We show that different macronutrients are not simply calories to be allocated to different traits, but directly determine the expression of different life-history traits and mediate their trade-offs. In this study, we also provide evidence that micronutrients influenced the expression of life-history traits, emphasizing the value of including micronutrients in experiments using nutritional geometry. A plain language summary is available for this article.