Associate Professor Utah State University, Utah, United States
Abstract: Predator-Prey dynamics have been studied across many different systems in both lab and field settings over the past 80 years. The outcomes of this past research have yielded many useful theoretical and empirical models of simple bi-trophic predator-prey systems. However, what stabilizes predator-prey dynamics is often debated and not well understood. For example, there is still a lack of consensus surrounding the Paradox of Enrichment, first proposed by Rosenzweig in 1971. Increasing our understanding of potential stabilizing mechanisms within predator-prey systems is important to better predict the consequences of changes in biodiversity due to climate change. One proposed stabilizing mechanism within predator-prey systems is the inducible defense mechanisms of prey which decrease trophic interaction strength. Due to the significant cost of these defenses, inducible defenses are not permanently expressed creating tradeoffs between increased survival and energy expenditure. Despite significant energetic costs, these defense strategies allow organisms to live under varying environmental and ecological conditions, making them more resilient to environmental change. In this study, we investigated the potential stabilizing effects of inducible morphological defenses in the protozoan, Paramecium aurelia under increasing nutrient enrichment. Using cox proportional hazard models, we found clone-specific effects of nutrient availability and predation threat on the survival of three different genetic clone populations of P.aurelia. Specifically, the survival of the clone population which exhibits an inducible defense (i.e., increasing body width in response to predation threat), was not significantly affected by either predator presence or available nutrients. These results suggest that when faced with both differing levels of nutrient availability and predator presence, the clone with an inducible defense was more likely to survive in comparison to populations that existed in a permanently defended or undefended state. These results demonstrate the flexibility of populations that exhibit inducible defenses to survive under varying environmental and ecological conditions. In conclusion, our study results show the positive effects of inducible defense mechanisms on the stability of populations and therefore communities under changing habitat conditions.
