Abstract
Selection may favour individuals of the same population to differ consistently in nutritional preference, for example, because optimal diets covary with morphology or personality. We provided Southern field crickets (Gryllus bimaculatus) with two synthetic food sources (carbohydrates and proteins) and quantified repeatedly how much of each macronutrient was consumed by each individual. We then quantified (i) whether individuals were repeatable in carbohydrate and protein intake rate, (ii) whether an individual’s average daily intake of carbohydrates was correlated with its average daily intake of protein, and (iii) whether short-term changes in intake of carbohydrates coincided with changes in intake of protein within individuals. Intake rates were individually repeatable for both macronutrients. However, individuals differed in their relative daily intake of carbohydrates versus proteins (i.e., ‘nutritional preference’). By contrast, total consumption varied plastically as a function of body weight within individuals. Body weight—but not personality (i.e., aggression, exploration behaviour)—positively predicted nutritional preference at the individual level as large crickets repeatedly consumed a higher carbohydrate to protein ratio compared to small ones. Our finding of level-specific associations between the consumption of distinct nutritional components demonstrates the merit of applying multivariate and multi-level viewpoints to the study of nutritional preference.
Highlights
Towards current reproduction, and are predicted to prefer carbohydrate-rich diets[14]
We quantified (i) whether individuals were repeatable in intake rate and nutritional preference, and (ii) whether an individual’s average daily intake rate of carbohydrates was correlated with its average daily intake of protein, and (iii) whether short-term changes in intake rate of carbohydrates coincided with changes in intake of protein within individuals[31,32]
When applying an alternative variance-partitioning approach to test for individual differences in nutritional preference, we found that the amount of carbohydrate intake was positively correlated with the amount of protein intake within individuals, whereas the among-individual correlation between average carbohydrate and protein intake did not significantly deviate from zero
Summary
Towards current reproduction (e.g., by courting females), and are predicted to prefer carbohydrate-rich diets[14]. We quantified (i) whether individuals were repeatable in intake rate (i.e., the total amount of each macronutrient consumed) and nutritional preference, and (ii) whether an individual’s average daily intake rate of carbohydrates was correlated with its average daily intake of protein (causing a so-called ‘among-individual correlation’), and (iii) whether short-term changes in intake rate of carbohydrates coincided with changes in intake of protein within individuals (causing a so-called ‘within-individual correlation’)[31,32]. We expected tight positive within-individual correlations, provided that total nutrient consumption varied plastically within individuals. We expected tight positive among-individual correlations, provided that individuals did not differ in nutritional preference. We further quantified whether intake rates (of carbohydrates and proteins) and nutritional preference were correlated with known proxies of proactivity (aggressiveness, exploration), mating activity, and body weight among- and within-individuals
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