Characterizing the (co)variance of personality traits in female Trinidadian guppies (Poecilia reticulata)

A fundamental question in behavioural and evolutionary ecology is to what degree individual phenotypic traits are variable over time and across ecological contexts and whether they are correlated with each other, as (co)variation in traits determines in part their responses to selection and rate of evolution. A first step to addressing this question is to characterize variation in behavioural traits within and among individuals and their covariation in particular ecological contexts. Here, we ascertained whether adult female guppies (Poecilia reticulata), descendants of wild guppies in Trinidad, are consistent or repeatable in their behaviour over time, such that they exhibit individual ‘personalities’ or behavioural types, and whether their personality traits are inter-correlated. Using a repeated-measures design, we twice assayed individual females for each of three ecologically important behavioural traits, Exploration (of a novel environment), Sociability (shoaling with conspecifics) and Boldness (risk taking), under standardized laboratory conditions. We characterized the among-individual (co)variance structure of each behavioural trait measure, and estimated their respective repeatability and the among-individual correlations between these traits using mixed-effects models. All three traits were found to be significantly repeatable and thus can be considered personality traits. None of the estimated correlations between all possible pairings of the three traits were significantly different from zero. Although adult female Trinidadian guppies from our study population exhibited repeatable personality traits, these traits were not inter-correlated (i.e. did not constitute a behavioural syndrome) and were thus independent of each other. Our findings have important implications for the maintenance of behavioural variation within populations and trait evolution.