Journal on Policy & Complex Systems Volume 2, Number 1, Spring 2015 - Page 67

Policy and Complex Systems - Volume 2 Number 1 - Spring 2015 Predator–Prey Dynamics and the Red Queen Hypothesis: Putting Limits on the Evolutionary Arms Race Ted CarmichaelA,B & Mirsad HadzikadicA Computer simulations of complex food webs are an important tool for deepening our understanding of these systems. Yet most computer models assume, rather than generate, key system-level patterns, or use mathematical modeling approaches that make it difficult to account for non-linearities. In this article, we present a computer simulation model that addresses these concerns by using agent-based modeling techniques, so that system-level patterns emerge from the interactions of thousands of individual simulated agents. In previous work, this model replicated fundamental properties of an ecosystem. This work extends the model in the context of the Red Queen hypothesis. We find that improvements in the competitive landscape for a single predator agent do not generally confer a benefit on the species as a whole, and may even be detrimental. Additional experiments that explicitly account for energy requirements and allow individual evolution illustrate how natural means limit arms races. This model can serve as a platform for evaluating policy options for developing sustainable systems, both in terms of long-term and short-term desired outcomes. Keywords: predator-prey, agent-based modeling, Red Queen hypothesis, evolutionary dynamics, population dynamics, complex adaptive systems. I - Introduction mathematical models, in order to determine whether resources fundamentally control species population (biomass)—as was the conventional wisdom at the time—or by predation. More recently, researchers have begun to ask, not which process (bottomup resources versus top-down predation) controls population overall, but rather how these two forces interact under different spatial and temporal scenarios (Reid, Battle, Batten, & Brander, 2000). Many scientists think that this new approach will help reveal how the combined effects of resourcemediated and predator-mediated forces influence the resilience of food webs (Casini et al., 2008). This suggestion leads naturally to the view that ecosystems can be productively T he literature on marine and terrestrial ecosystems is extensive and diverse, encompassing both theoretical models and empirical surveys (Christensen et al., 2003; DeAngelis & Mooij, 2007; Frank, Petrie, Choi, & Leggett, 2003; Grimm, 1999). Some significant differences between model results and real-world surveys have persisted for years, and it has been difficult identifying fundamental principles relative to the many complicating factors within existent ecosystems. For example, in the early 1980s, Oksanen, Fretwell, Arruda, and Niemelä (1981) examined multiple trophic levels in a predator–prey system using A B Department of Software and Information Systems, UNC Charlotte, Charlotte, NC 28223, USA TutorGen, Inc., Fort Thomas, KY 41075, USA 10.18278/jpcs.2.1.7 65