2) How do predators affect disease dynamics in their prey? Experimental tests of the healthy herds hypothesis with fish predators, zooplankton hosts, and a fungal parasite

The host, Daphnia dentifera. The top and second from bottom are infected by the fungus Metschnikowia bicuspidata, turning the host darker.

Mentors: Dr. Robbie Richards and Dr. Alex Strauss
Abstract: Food web members can dramatically impact host-parasite dynamics through a wide variety of mechanisms. The “healthy herds hypothesis” posits that predators can substantially decrease parasitism in their prey by directly consuming infected individuals. However, experimental tests of this idea remain rare. Moreover, the few experiments that have been attempted have yielded inconsistent results, with predators sometimes decreasing disease, increasing disease, or having no effect on disease in their prey. Reconciling these divergent outcomes is increasingly important as prey species serve as reservoirs for many diseases of concern for spillover into human populations. In this project you will have the opportunity to conduct a large-scale manipulative experiment to test the healthy herds hypothesis. We will use a replicated mesocosm (i.e., artificial pond) system of mosquitofish predators, fungal parasites and their shared host/prey, the water flea, Daphnia dentifera. Finally, we will measure several key traits (e.g., preference of fish for infected vs. healthy hosts) and ask whether they explain why predators increase, decrease, or have no effect on disease in the experiment.
Is the project computational, empirical, or both? Mostly empirical, but with opportunities to learn computational skills such as model fitting and parameterization.