David Joseph Mitchell, Christa Beckmann, Peter A Biro

Predation is increasingly viewed as an important driver in maintaining ecological and phenotypic diversity. In contrast to classic evolutionary theory which predicts that predation will shift trait means and erode variance within prey species, several studies indicate higher behavioural trait variance and integration in high predation populations. These results come predominately from field-sampled animals that cannot isolate the role of predation from other ecological factors such as density. Here, we study the role of predation on behavioural trait (co-)variation in density-controlled populations of guppies (Poecilia reticulata) living with and without a benthic ambush predator. At 2.5yrs post introduction of the predators (up to 10 overlapping generations), 40 males were sampled from each of the six populations and extensively assayed for activity rates, water-column use and voracity. Individual variation was pronounced in both treatments, with substantial individual variation means, temporal plasticity and predictability. The effects of predation were subtle. Predators had little effect on mean behaviour, though predator-exposed fish spent more time at the surface in early trials, which decreased to the same as controls with time. Predators did however affect the integration of behavioural traits. In predator exposed ponds, guppies that were higher in the water-column fed slower and had a reduced positive correlation with activity, relative to control populations. Predators also affected the integration of personality and plasticity – leading to changes in among-individual variances through time in water-column use and activity – which was absent in controls. Our results contrast with the extensive guppy literature showing rapid evolution in trait means, and shows maintenance of behavioural variance under predation.