Assistant Professor / AAAS Science & Technology Policy Fellow University of Texas at Austin / NASA, United States
Parasitic infections are incredibly common, but how they shape ecosystem-level processes is understudied. Emerging evidence suggests that parasites, including microparasites (bacteria, fungi, protozoa, and viruses) and macroparasites (helminths and arthropods) trigger trophic cascades in similar ways to predators. Both predators and parasites can have cascading effects on ecosystems by killing their victims or by causing sublethal harm to victims prior to exploitation. However, unlike predators, parasites also modify victim traits by consuming but not killing their hosts. Given that nearly all organisms have long-lasting, intimate associations with a multitude of parasites, the extent to which parasites impact ecosystems by triggering trophic cascades is a clear gap in our understanding of how animals influence biogeochemical cycles. A better understanding of the effects of parasites is especially critical because changing environmental conditions are currently affecting the abundance and diversity of parasitic species across the globe. This presentation will explore various pathways by which parasites might indirectly alter elemental cycling. Building on this understanding, I will use two case studies to explore how infections can influence carbon cycling in helminth-ruminant systems. The first shows the potential for parasites to exacerbate methane production by ruminant livestock, while the second demonstrates how pervasive parasitic infections reduce herbivory rates of free-living ruminant hosts. In both examples, evidence suggests there are widespread, but overlooked, ecological consequences of sublethal infections in natural and managed systems. These and other recent efforts to link the fields of disease ecology and ecosystem ecology highlight a need to better characterize the broader ecological roles of parasites.
