ORIGINAL PAPER Complementary predation on metamorphosing species promotes stability in predator–prey systems Ezer Miller & Moshe Coll & Lewi Stone Received: 13 January 2009 / Accepted: 6 October 2009 # Springer Science + Business Media B.V. 2009 Abstract Functionally redundant predation and functionally complementary predation are both widespread phenomena in nature. Functional complementary predation can be found, for example, when predators feed on different life stages of their prey, while functional redundant predation occurs when different predators feed on all life stages of a shared prey. Both phenomena are common in nature, and the extent of differential life-stage predation depends mostly on prey life history; complementary predation is expected to be more common on metamorphosing prey species, while redundant predation is thought to be higher on non-metamorphosing species. We used an ordinary differential equation model to explore the effect of varying degree of complementary and redundant predation on the dynamic properties of a system with two predators that feed on an age-structured prey. Our main finding was that predation on one stage (adult or juvenile) resulted in a more stable system (i.e., it is stable for a wider range of parameters) compared to when the two predators mix the two prey developmental stages in their diet. Our results demonstrate that predator–prey dynamics depends strongly on predators' functionality when predator species richness is fixed. Results also suggest that systems with metamorphosing prey are expected to be more diverse compared to systems with non-metamorphosing prey. Keywords Predator–prey population dynamics . Age-structured predation . Functional redundancy/ complementary . Metamorphosis Introduction Functionally redundant organisms do similar things in the ecosystem, while functionally complementary species do different things (Casula et al. 2006). Functionally complementary predation can be found for example when predators feed on different life stages of their prey, while functionally redundant predation happens when different predators attack all life stages of their shared prey (Casula et al. 2006; Wilby and Thomas 2002). Since many organisms occupy different habitats at different developmental life sages, their predators may be operating in complementary or redundant ways (Casula et al. 2006; Wilby and Thomas 2002). It is not clear, however, how these modes of predation affect the dynamics of predator–prey systems. The degree by which predators are redundant or complementary in their actions is central for ecosystem functioning and is likely to be influenced by the prey's life history. Indeed, many animals exploit markedly different habitats as juveniles and adults. This is particularly apparent in amphibians, fish, marine invertebrates, and many holome- tabolous insects (Fox et al. 2001; Gilbert and Frieden 1981; Margulis and Schwartz 1997). It is common for marine invertebrates to live as free swimmers in the juvenile stage and as bottom dwellers as adults (Fox et al. 2001; Gilbert and Frieden 1981; Thorson 1950), and adult amphibians are E. Miller (*) : M. Coll Department of Entomology, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot 76100, Israel e-mail: miller@agri.huji.ac.il M. Coll e-mail: coll@agri.huji.ac.il L. Stone Department of Zoology, Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel e-mail: lewi@post.tau.ac.il Theor Ecol DOI 10.1007/s12080-009-0059-z