Meeting Abstract
The interaction between predators and their prey represents the classic evolutionary arms race – any improvements in predator performance that make prey capture more likely should be countered by improvements in prey escape abilities. In this study, we tested the prediction that the evolution of prey speed depends on the energetic costs associated with their capture by a predator. We developed a dynamic computer game to quantify the rate and direction of evolutionary change in prey escape speeds. We asked humans (i.e. predators; N=150) to capture as many uniformly sized dots (i.e. prey; N=100) as possible as they moved singly across a computer screen. Prey speed varied up to four-fold among individuals and they were captured by clicking on them with a mouse. Surviving prey then reproduced (3 clonal offspring each), and a new generation of 100 individuals was sourced at random from these offspring. This was repeated for six generations. Human subjects were randomly assigned into one of 3 treatments, representing low, moderate and high costs associated with prey capture. Subjects were asked to maximize energetic gains, taking into account that each successfully captured prey earned 10 energy units, while each attempt to capture prey (successful or not) cost 1, 2 or 5 energy units, depending on treatment group. We expected that if the costs of prey capture were low, then prey would be captured across all speeds and the evolution of prey speeds would slower and less directional. However, if the costs of prey capture were high, then only the slowest prey within a population would be captured, promoting directional and rapid selection of prey speed. After six generations , we were able to determine how the average and frequency distribution of prey speed within a population evolved in response to the costs of prey capture.
