Developing, unifying, and empirically testing theory for inducible and evolving defenses

Florida State University, Tallahassee FL

Investigators

Abstract

Throughout the world, prey species have a variety of defenses to avoid being eaten by predators. Plastic defenses are those that can change over time based on how many predators are present, for example prey may spend more time hiding when there are more predators around. Evolving defenses (like shell thickness) change over time based on which parents survive to reproduce and are able to pass their traits to their offspring. These different types of defenses influence the abundances of prey and their predators, as well as responses to environmental change. However, it is unclear exactly what effects plastic and evolving defenses have and whether plastic and evolving defenses have similar or different effects on species abundances and their responses to environmental change. Developing such an understanding is important because humans are dramatically altering environments through nutrient enrichment and species mortality. At present, it is not possible to predict how different types of defense (plastic or evolving) determine how populations will respond. This project uses laboratory experiments and mathematical models to determine how different types of plastic and evolving defenses influence population abundances and how populations respond to environmental change. This research program will train undergraduate and graduate students in the fields of community ecology and mathematical biology, engage underrepresented minorities in research, and engage the public through community outreach activities. Adaptive responses in prey to predation pressure can be plastic or evolutionary in nature, and both can alter the dynamics and stability of ecological communities. The goal of this project is to develop theory that explains how mechanistic differences between different types of plastic defenses and evolving defenses shape the dynamics of communities. To identify when plastic and evolving defenses have similar versus different effects, mathematical models will be developed to explain how plastic and evolving defenses influence system stability and population responses to nutrient enrichment and species mortality. The theory will be tested via laboratory based experiments involving populations of a prey species (Paramecium) that do or do not have plastic defenses - changes in behavior and body width - that alter the rate at which they are consumed by predators. This work will both extend current theory for plastic defenses and unify it with the theory for evolving defenses. The theory-data pairing approach of this project is likely to generate important advances in the theory of plastic defenses and community ecology. This work will also yield insight into the connections between plastic and evolutionary adaptation. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.