Effects of host community structure on parasite transmission and disease risk

Abstract

This thesis aims to determine how parasite transmission responds to temporal, spatial, or ecological factors such as host biodiversity. For this study, I used a fathead minnow/trematode parasite study system and incorporated both field and experimental components. Long-term data on the parasite population sizes in fathead minnows from two lakes in Alberta indicate that parasite population sizes are highly variable. Simultaneous infections by multiple parasite species in fathead minnows is the norm, with closely related parasite species exhibiting similar long-term trends in population dynamics. Increases in host biodiversity is thought to decrease parasite transmission, however, my experiments indicate that biodiversity is not directly causing a decrease in transmission of the trematode Ornithodiplostomum ptychocheilus into fathead minnows. Instead, I suggest that the mechanism behind the decline in transmission is the species-specific modulation of transmission pathways as host biodiversity increases.