On multiple infections by parasites with complex life cycles

Abstract

Host manipulation is a common strategy of parasites with complex life cycles. It directly affects predator–prey dynamics in trophically transmitted parasites. Theoretical studies suggest that predation-enhancing manipulation often decimates the prey population, making parasites prone to extinction. Host manipulation, however, can also reduce predation due to conflicting interests when multiple parasites infect a host, which is often neglected in theoretical studies. Misaligned interests of coinfecting parasites can occur due to limited carrying capacity or parasitoid developmental stage. Including this realistic complexity in a mathematical model, the results depart from previous studies substantially. We show that coinfecting multi-trophic parasites can preserve the predator–prey system and themselves through manipulation and reproduction parameters. Our study highlights the necessity of and provides the means for incorporating the reality of multiple parasites and their multi-trophic life cycles into the theory of parasite ecology.