ABSTRACT

Insect communities are structured by the biotic interactions between generalist insect predators and their prey. Among insect predators, three general feeding methods are used (mandibles, raptorial forelegs, and unmodified legs) to capture prey, which usually consists of herbivorous insects. In this game, students play the role of three types of insect predators as they forage upon three potential prey species (represented by three different types of candy). Students conduct 5-10 simulations each of which lasts about 45 seconds. After each simulation, prey reproduce based on the number remaining, and predator numbers are adjusted to reflect mortality and reproduction. In insect communities, prey species may evolve defenses, including poisons, in response to strong predation pressure. However, costs of these defenses might include slowed growth and reduced reproduction rates. In this game, one prey type becomes poisonous, but suffers a lowered rate of reproduction, while the other types remain palatable and have higher rates of reproduction. If the predator type that suffers the greatest mortality evolves to feed on poison-protected prey species, all three predator types are maintained in the community. Otherwise, one or more of the predator species may go extinct. Discussion of the results, presented graphically, allows students to understand how evolutionary tradeoffs influence community structure and function.

AUTHORS

W. Wyatt Hoback

Department of Biology, University of Nebraska at Kearney, Kearney, NE 68849. email: hobackww@unk.edu

Tamara L. Smith

Department of Biology, University of Nebraska at Kearney, Kearney, NE 68849.

CLASS TIME

The exercise takes between 2 and 3 hours, which includes time for data analysis. Extra time will be needed for extension activities.

OUTSIDE OF CLASS TIME

Students will need 1-2 hours to answer questions and write reports, with extension activities requiring more time.

STUDENT PRODUCTS

Students answer questions from the completed worksheet and graphs. Students may complete a report on how a community will evolve when driven by predator-prey relationships. As part of the extension activities, students can develop their own predator-prey system, choosing initial numbers of predators and prey, as well as prey and habitat type.

SETTING

This is an indoor laboratory; it can easily be adapted to the outdoors.

COURSE CONTEXT

This laboratory exercise is used for non-majors biology courses. It has also been used with high school biology and middle school science students. With extensions and student-determined rules for the game, the exercise could be used for majors courses in ecology and evolution.

INSTITUTION

Mid-sized four-year public university with undergraduate and master's degree options.

TRANSFERABILITY

This activity can be used with both majors and non-majors in biology and entomology. Extension activities add to the difficulty level and are appropriate for students studying ecology.

ACKNOWLEDGMENTS

This activity was created while at the University of Nebraska at Lincoln in conjunction with Leon G. Higley, who provided many useful suggestions. The exercise was first presented at a meeting of the Association of Biology Laboratory Educators and was published in modified format in ABLE Workshop/Conference Proceedings: Tested Studies for Laboratory Teaching Vol. 21: 293-304 (Hoback 2000, http://www.zoo.utoronto.ca/able/volumes/volume21.htm). We would like to thank two anonymous reviewers and Christopher Beck for suggestions that greatly improved this exercise. We would also like to thank Rick Simonson for his work on the illustrations.

CITATION

W. Wyatt Hoback, Tamara L. Smith. April 2006, posting date. The Insect Predation Game: Evolving Prey Defenses and Predator Responses. Teaching Issues and Experiments in Ecology, Vol. 4: Experiment #3 [online]. http://tiee.ecoed.net/vol/v4/experiments/insect_predation/abstract.html