PI Name: Priyanga Amarasekare Institution: University of Chicago
This research investigates how multiple predator and parasite species influence the dynamics (change in abundance) of their common prey or host species. The ecological system that is the focus of research is the harlequin bug and two parasitoid species (parasitic insects that grow on and kill other insects) that attack the bug's eggs in southern California. The system presents a puzzle: multiple parasitoid species can coexist on the same host stage as well as reduce fluctuations in host abundance. Solving the puzzle requires understanding the mechanism(s) by which both parasitoid species coexist on a single host species, and how these mechanism(s) in turn influence the parasitoids' effect on the host. The first goal is to distinguish between two hypotheses that address mechanisms of parasitoid coexistence are intraguild predation (IGP) and temporal niche partitioning (TNP). Intraguild predation predicts that species will coexist because one species is superior at attacking unparasitized hosts while the other species is superior at attacking hosts already parasitized by the first (multiparasitism). Temporal niche partitioning predicts that species will coexist because each is superior at attacking hosts at different times of the year. Predictions for the two hypotheses will be tested via manipulative field experiments. Understanding how coexisting parasitoid species influence host population dynamics will be the domain of mathematical models that explore the impact of parasitoids on host abundance and variability under different mechanisms of coexistence (IGP vs. TNP). This research is novel because it investigates how multiple consumer species influence the dynamics of a shared resource, a poorly understood issue that is critical to the maintenance of species diversity. It also has applied significance. The decision to release single or multiple natural enemies to control a pest, an issue at the heart of biological pest control, depends crucially on the mechanisms by which natural enemies coexist on a given pest species. Linking mechanisms of resource use with population dynamics allows us to predict which combinations of natural enemies provide the most effective control of a pest.
