Predator-induced phenotypic plasticity of laterality

• Predation could select for a higher degree of laterality.
• We tested guppies from high- and low-predation environments using a common garden split-brood design.
• Half of the guppies were exposed to chemical predator cues during rearing.
• Historical predation regime, or evolutionary history, had no effect on laterality.
• Guppies reared with predator cues were more highly lateralized.

Lateralized brain function, or partitioning of tasks to separate hemispheres of the brain, directly impacts behaviour and fitness. Highly lateralized individuals tend to outperform nonlateralized individuals in many survival-related behaviours, such as the ability to learn, escape predators and multitask. Despite these benefits to lateralization, there is a great deal of observed variation in this trait within and between populations that is likely determined by the balance between costs and benefits of laterality in a given environment. Laterality appears to be heritable, but it can also vary with the environment experienced during development. We investigated the role of evolutionary history and developmental plasticity in determining the degree of laterality in the Trinidadian guppy, Poecilia reticulata, a freshwater fish that experiences variable predation pressure in its native range. We compared pairs of closely related populations that experience either high or low levels of predation in the wild, and manipulated the perceived predation risk in the rearing environment using a common garden split-brood design. We assayed laterality in mature male guppies using a detour test. Fish reared with exposure to chemical predator cues were more lateralized than their brothers reared without predator cues. This plastic response is in the direction we would predict if lateralization is favoured in environments with high predation risk. However, unlike findings in related species, we did not detect repeatable differences in degree of laterality associated with historical predation regime, suggesting that predation risk experienced over evolutionary history does not shape laterality patterns in guppies. Thus, although it is currently underemphasized in the literature, plasticity is likely an important contributor to variation in laterality.