INTERDISCIPLINARY AMAZON BASIN JIGSAW EXERCISE: WHY DOES THE AMAZON BASIN EXHIBIT SUCH HIGH BIODIVERSITY?

In this exercise, given to an upper-division geomorphology class during one three-hour class, the primary goal was to illustrate the interdisciplinary nature of geosciences today. Secondly, factors potentially causing paleoenvironmental change, thus impacting speciation in the Amazon basin were illustrated. Students applied the scientific method, critically assessing data and testing it against multiple hypotheses; they realized that ideas change, debates ensue and apparently established solutions are in reality dynamic and shifting.

The class was divided into 6 groups of three, each of which became an Expert Group in an assigned subject: eolian dunes, fluvial sediments, tectonic uplift, speciation, climate change or biogeography. Given assorted reading materials and questions related to each hypothesis, becoming an expert required literary research.

Subsequently, students were divided into 3 teams of six, each having every type of Expert. Each team was assigned an hypothesis, appropriate readings, and basic arguments for and against other hypotheses. Teams were given time to familiarize themselves with the material, and then they debated the relative merits of each hypotheses. Individuals handed in answers to specific questions testing their understanding of the discussion and preliminary work.

Recent explanations of biodiversity in the Amazon basin include a refutation of the long-accepted Refugia Hypothesis (HAFFER 1969, Science, 165:131-137) with the Non-Refugia Hypothesis (COLINVAUX et al. 2000, Quaternary Science Reviews, 19:141-169), which argues for little Quaternary climatic change but ever-changing species assemblages. What we termed the 'Stable Variability Hypothesis' (HOOGHIEMSTRA and VAN DER HAMMEN 1998, Earth-Science Reviews, 44:147-183) combines these hypotheses with changes wrought by the uplift of the Andes and subsequent changes in fluvial and coastal geomorphology. Seven species of the Cotingidae family of arboreal birds were used as an example of high biodiversity.

This exercise worked on many levels; problems with presentation and execution will be addressed. Students enjoyed its interdisciplinary nature and the fact that it was cutting edge: the hypotheses are exactly that, as none has yet been proven.