Meandering mealworm metapopulations in mesocosms go horizontal

Background/Question/Methods

Horizontal linkages in the curriculum tie together important concepts and skills within a semester. An important but difficult concept may be introduced in one course, developed in a second course and then repeated in a slightly different context in a third course. Depending on each concept’s difficulty and importance, this process may go through several iterations. We present a new, inexpensive laboratory activity that can be used to address questions about metapopulation ecology and island biogeography (or ideal free distributions and animal movement). It has been taught in the freshman ecology course for biology majors, and will be horizontally linked to a freshman seminar course, and an introductory mathematics course designed specifically for biology majors.

Results/Conclusions

The laboratory establishes populations of mealworm beetles, Tenebrio molitor, within a 1.5 m² mesocosm. The habitats are piles of bran, which rest on a matrix of smooth wallboard. In a pilot study students read an article that presented the basic tenets of metapopulation ecology, and then designed a set of mesocosms that addressed questions based on their reading. Their designs varied connectivity, habitat size or initial population density, testing the hypotheses that high connectivity, large habitat size and high population density would increase immigration rates into new habitats. Both connectivity and habitat size influenced immigration rates into new habitats, but initial population density did not. We discuss plans to link this laboratory horizontally into a new biology curriculum. Readings and experimental design will be discussed in the freshman seminar course and in the ecology course. Students will also fit an exponential decay curve to their observations of mealworm emigration from a central habitat. Exponential growth and decay curves are taught in the new math for biologists course, and reinforced in the ecology course in discussions of population growth, radioactive decay and decomposition. These explicit linkages provide a rich biological context for students developing their quantitative and analytic skills.