Data for: Genetic and context-specific effects on individual inhibitory control performance in the guppy (Poecilia reticulata)

Among-individual variation in cognitive traits, widely assumed to have evolved under adaptive processes, is increasingly being demonstrated across animal taxa. As variation among individuals is required for natural selection, characterising individual differences and their heritability is important to understand how cognitive traits evolve. Here we use a quantitative genetic study of wild-type guppies repeatedly exposed to a ‘detour task’ to test for genetic variance in the cognitive trait of inhibitory control. We also test for genotype-by-environment interactions (GxE) by testing related fish under alternative experimental treatments (transparent vs. semi-transparent barrier in the detour-task). We find among-individual variation in detour task performance, consistent with differences in inhibitory control. However, analysis of GxE reveals that heritable factors only contribute to performance variation in one treatment. This suggests that the adaptive evolutionary potential of inhibitory control (and/or other latent variables contributing to task performance) may be highly sensitive to environmental conditions. The presence of GxE also implies that the plastic response of detour task performance to treatment environment is genetically variable. Our results are consistent with a scenario where variation in individual inhibitory control stems from complex interactions between heritable and plastic components.

Methods
Data was collected from fish bred from a captive population of P. reticulata housed at the University of Exeter’s Penryn campus. The population has been maintained at a population size of several thousand, with no deliberate selection or inbreeding. Behavioural data was collected on an offspring generation of 374 guppies (all tested as adults), produced from 6 small breeding groups over a period of 4 months.  Individual detour task performance was assessed in a repeated measures design. First, naïve guppies were given the opportunity to learn to associate the appearance of a green disc placed on the floor of the test compartment with a food reward. Individual guppies were given nine feeding training ‘trials’ (3 per day for 3 successive days). To ensure fish had sufficient opportunity to learn the food location, they did not proceed to the detour task if they did not locate food in 5/9 of the training trials. Fish that completed the training stage were then assayed three times in a detour task (once per day for three successive days), and time taken to locate a food reward inside a cylinder was recorded. To test for GxE, fish were assigned to one of two treatments in the detour task; either a transparent (unmarked) cylinder with low visual information or a cylinder marked with three black horizontal lines providing high visual information. 

Fish were genotyped at 6 autosomal microsatellite loci to facilitate pedigree reconstruction.

Data from both detour and training trials were analysed using a linear mixed effect model fitted with ASReml-R 4.1 within R version 3.6.1.