Quantifying Effects of Parasites on Ecosystem Nutrient Cycling

Parasites are infamous for their direct negative effects on host individuals and populations. However, parasite effects on host behavior, physiology, and demography could also have far-reaching effects on ecosystem-level processes such as carbon and nitrogen cycling. For example, parasites may indirectly alter the flow of energy and nutrients through ecosystems by reducing host densities (i.e., by killing hosts or reducing their rates of reproduction), altering host traits (e.g., foraging behavior and landscape use), and modifying the ways in which hosts process nutrients. A framework for quantifying such effects is critical as changing environmental conditions affect the abundance and diversity of parasitic species across the globe (up to 1/3 of global parasite diversity is projected to go extinct within the next 50 years).

Our interdisciplinary working group of disease ecologists, animal health specialists, community and ecosystem ecologists, and theoreticians will develop such a framework to address how parasites affect ecosystem nutrient cycling by using ungulates (hoofed mammals) and their diverse parasites as a model. Ungulates are a globally distributed group of mammals that occur in almost every biome. They occupy central positions in food webs as key primary consumers and prey for secondary consumers. Many have large impacts on ecosystems via herbivory, as well as through nutrient deposition from waste products and carcasses. Together, these traits make ungulates an excellent starting point for exploring how individual- and population-level effects of diverse parasites translate to the ecosystem level.

Publications

Ezenwa, V.O., Civitello, D.J., Barton, B.T., Becker, D.J., Brenn-White, M., Classen, A.T., Deem, S.L., Johnson, Z.E., Kutz, S., Malishev, M. Penczykowski, R.M., Preston, D.L., Vannatta, J.T., and Koltz, A.M. (2020). Infectious diseases, livestock, and climate: a vicious cycle? Trends in Ecology & Evolution, 35(11), pp.959-962. doi: 10.1016/j.tree.2020.08.012

Ezenwa, V.O., Civitello, D.J., Classen, A.T., Barton, B.T., Becker, D.J., Brenn-White, M., Deem, S.L., Kutz, S., Malishev, M., Penczykowski, R.M., Preston, D.L., Vannatta, J.T., and Koltz, A.M (2021). Response to Charlier et al.: Climate–Disease Feedbacks Mediated by Livestock Methane Emissions Are Plausible. Trends in Ecology & Evolution, 36(7), pp.578-579. doi: 10.1016/j.tree.2021.04.005

Koltz, A.M., Civitello, D.J., Becker, D.J., Deem, S.L., Classen, A.T., Barton, B., Brenn-White, M., Johnson, Z.E., Kutz, S., Malishev, M., Preston, D.L., Vannatta, J.T., Penczykowski, R.M., and Ezenwa, V.O. (2022). Sublethal effects of parasitism on ruminants can have cascading consequences for ecosystems. Proceedings of the National Academy of Sciences, 119(20), p.e2117381119. doi: 10.1073/pnas.2117381119

Research Team

Amanda Koltz, WashU (Biology)
Sharon L. Deem, Saint Louis Zoo
Vanessa O. Ezenwa, University of Georgia
Rachel Penczykowski, WashU (Biology)