Community and Ecosystem Level Implications of Helminth Parasitism

Pathogens and parasites are increasingly recognized as important components within host populations, communities, and ecosystems. Parasite contributions to ecosystem function most likely manifest as density-mediated impacts of parasites on their hosts, the direct contributions of parasite biomass to a system, and via parasite-induced changes in host behavior and physiology (trait-mediated impacts). Here, a framework was constructed that can be used to conceptualize parasite contributions to ecosystem function (Chapter 1). Then the influence of parasite attack on host movement was explored to further evince the mechanistic underpinnings of trait-mediated parasite impacts (Chapter 2). Additionally, mesocosms were created across a gradient of parasitism to examine how these mechanisms are likely to unfold at larger biological scales (Chapter 3). Lastly, a series of differential equations was created to model host-parasite-ecosystem interactions and generate theoretical predictions about how and when parasites are likely to influence ecosystem processes (Chapter 4). Parasites have many characteristics of ecosystem engineers, but their role has historically been ignored. These studies begin to explore the role that parasitism may have as one of the drivers of ecosystem processes.