Pace-of-life syndrome: linking personality, metabolism and colour ornamentation in male guppies

Abstract

Within populations, there commonly exists consistent among-individual differences in behaviour. As a potential mechanism maintaining this variation, the pace-of-life-syndrome (POLS) hypothesis posits that consistent differences in the behaviour of individuals (i.e. ‘personality’) are intercorrelated and have coevolved with consistent individual differences in metabolism and life-history traits. Here, using adult male guppies, Poecilia reticulata , we tested under laboratory conditions (1) whether behavioural and metabolic traits vary consistently among individuals over time (≤7 days) and (2) the POLS prediction that repeatable behavioural traits should be intercorrelated with each other and with repeatable metabolic rate at the among-individual level. Furthermore, based on indicator models of sexual selection, we expected that sexually selected male colour ornamentation would predict individual personality and metabolic rate. We repeatedly assayed three behavioural traits (sociability, boldness, exploration) and three metabolic traits (resting metabolic rate, maximal metabolic rate, aerobic scope) in a set of males that varied in body size and colour ornamentation. All behavioural trait measures were repeatable, consistent with individual personality. Of the three metabolic traits, only resting metabolic rate (RMR) was repeatable. Behavioural trait measures were significantly intercorrelated and thus integrated in a behavioural syndrome. More ‘proactive’ males were bolder, more exploratory and more sociable than ‘reactive’ ones. However, contrary to the POLS hypothesis, RMR was not significantly correlated with any of the behavioural trait measures, suggesting that consistent individual differences in RMR do not drive or support differences in personality, or vice versa. Male colour ornamentation did not covary with behaviour or RMR and thus does not appear to be a reliable predictor of either behavioural or metabolic phenotypes. We therefore did not find any compelling support for the POLS hypothesis, suggesting that individual differences in metabolism do not underlie the evolution and maintenance of among-individual behavioural variation in our study population. • We tested for behaviour–metabolism covariation in guppies (pace-of-life syndrome, POLS). • Behaviour and resting metabolic rate (RMR) differed consistently among males. • Behavioural differences between males, however, did not covary with their RMR. • Male colour ornamentation did not predict either their personality or metabolism. • Overall, our results do not support the central prediction of the POLS hypothesis.