This exercise, intended as homework or an in-class exercise, provides a guided inquiry approach to understanding continental scale patterns of species richness and patterns of relative abundance within community species assemblages. Students are introduced to the concept of latitudinal gradients in species richness. They are also introduced to the concept of evenness of relative abundances within a community assemblage, and how empirically it is often true that species rich communities have more even relative abundances of the constituent species. The students are then assigned a homework exercise to examine whether the patterns of relative abundances show the same latitudinal biogeographic pattern as species richness. The exercise uses the Science Pipes platform (www.sciencepipes.org) that extracts data from the US Forest Service Forest Inventory & Analysis (FIA) Program. Students are tasked to do four latitudinal transects, each consisting of a total of one county from each of four different states along the same longitude. The students generate rank abundance curves and associated data tables for each of the counties included in their transects. The students examine the patterns of the sixteen rank abundance curves among the four transects. From these data, the students evaluate whether (1) species richness varies inversely with latitude and (2) whether evenness of relative abundances parallels the latitudinal pattern of species richness. They also evaluate whether (3) coastal locations have higher species richness and evenness than continent interior locations. The exercise is designed as a homework assignment, but can also be done in class.
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