Diet composition does not affect ant colony tempo

Summary 1. Resource availability can influence the structure of animal communities by mediating competitive interactions. An underappreciated aspect of resource ecology is how functional traits are built from particular sets of nutrients and thus are underexpressed when those nutrients are scarce. 2. One idea linking resource availability to competition is the metabolic fuel hypothesis, which posits that access to carbohydrate-rich resources favours high activity rates that increase competitive prowess. One prediction of this hypothesis is that an increase in dietary carbohydrate richness will lead to an increase in consumer metabolic rate (MR). An alternative prediction is that carbohydrate-rich diets will affect biochemical storage. 3. We tested these predictions by examining the effect of dietary protein : carbohydrate (P : C) ratio on the feeding behaviour, demography, physiology and MR of colonies of Ectatomma ruidum, a common tropical ant. We found that rearing colonies for 6 weeks on different P : C diets altered colony demography and worker storage biochemistry, but higher carbohydrate intake did not result in an increase in whole-colony MR. 4. Our results suggest that dietary carbohydrates may increase colony dominance through changes in colony composition and individual worker longevity rather than changes in worker activity rates. More generally, they illustrate how the identity of scarce nutrients can have particular effects on traits that impact ecological interactions.