This exercise in community ecology can be carried out in mid-winter and introduces participants to useful taxonomic and statistical procedures.
Ecologists often study the dynamics of single-species populations or the interactions between two species, but real ecological systems comprise multiple species. Unique effects arising from the complexity of having more than two species present are termed indirect effects: effects of one species on a second species that arise only in the presence of one or more other species. In this laboratory, we will observe guppies foraging on Daphnia in the presence and absence of aquatic plants to test for indirect effects of the plant species on the predator-prey interaction.
Light is often a limiting resource for plants, which can be stimulated to higher photosynthetic rates and higher growth rates by increasing the amount of light they receive. However, many plants are well adapted to living in low-light environments, like the shaded understory of a forest. In this lab, students test working hypotheses about the photosynthetic responses of representative pioneer and primary forest tree species that might account for the successional patterns observed in the forest. Students collect data on light intensity in gap and understory patches, on growth rates of representative pioneer and primary species, and on photosynthetic rates of representative species under gap and understory light conditions.
This field and laboratory investigation is an open-ended exercise designed to test predictions from island biogeography theory using various-sized fragments of leaf litter arthropod communities as "island" systems. Litter islands are constructed in a deciduous forest and students collect samples of leaf litter and extract arthropods using the Berlese Funnel technique. After arthropods are collected, students learn identification techniques, compute diversity indices, construct dominance-diversity and species area curves, and draw conclusions about the effects of fragment size and insularity on arthropod community diversity.
