No abstract

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 http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.13190/suppinfo is available for this article.

In animals, commensal microbes modulate various physiological functions, including behavior. While microbiota exposure is required for normal behavior in mammals, it is not known how widely this dependency is present in other animal species. We proposed the hypothesis that the microbiome has a major influence on the behavior of the vinegar fly (Drosophila melanogaster), a major invertebrate model organism. Several assays were used to test the contribution of the microbiome on some well-characterized behaviors: defensive behavior, sleep, locomotion, and courtship in microbe-bearing, control flies and two generations of germ-free animals. None of the behaviors were largely influenced by the absence of a microbiome, and the small or moderate effects were not generalizable between replicates and/or generations. These results refute the hypothesis, indicating that the Drosophila microbiome does not have a major influence over several behaviors fundamental to the animal’s survival and reproduction. The impact of commensal microbes on animal behaviour may not be broadly conserved.