Paleoecological exercise: Testing competition among Paleozoic brachiopods

David C Kendrick
,
Hobart & Wm Smith Colleges
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Summary

This lab activity tests the hypothesis that competition has resulted in niche partitioning among four species of brachiopods.

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Context

Audience

This is an upper-division course for geology majors and minors, however, interested students from all disciplines who have satisfied the prerequisites are welcome. The prerequisite is the introductory physical geology course; having the earth history course is desirable but not required. The course has a required three-hour laboratory and two weekend field trips.

Skills and concepts that students must have mastered

1. Basic ecological concepts like competition and niche partitioning
2. Basic brachiopod biology and ecology (i.e. things like what is the commissure, they are filter feeders, what resources are limiting)
3. Basic algebra
4. Basic statistics

How the activity is situated in the course

This is a stand-alone exercise, but dovetails well with lecture units on paleoecology, competition, and testing hypotheses, as well as part of continuing practice on synthesizing results and summarizing material in abstract form.

Goals

Content/concepts goals for this activity

Competition
Niche partitioning
species identification
accurate measurement

Higher order thinking skills goals for this activity

data analysis
hypothesis testing

Other skills goals for this activity

synthesizing results
abstract writing
statistical calculations and testing
computer spreadsheet use

Description of the activity/assignment

Students use the procedure outlined by Casey Hermoyian and colleagues (2002) to test whether competition played a role in structuring a strophomenid brachiopod community in the Middle Devonian Onondaga limestone of western New York. It is not necessary to use these particular brachiopods; brachs from other localities, ages, and species could work, too, if chosen well. Students sort through a collection of brachiopods, separating them into groups of species defined by mutual agreement. They then use measurements of the commissure length to test two predictions made by Robert MacArthur's (1972) theory of how Hutchinson's (1959) niche partitioning would be evidenced: nonoverlapping resource use among former competitors but with very little distance between them. Students graph results, calculate ratio sums of their measurements and z statistics to test whether their results are significant. Finally, students prepare a conference-type abstract based on their results. The activity gives students practice in observing differences among groups, measurement, graphing, statistical calculation, synthesizing results, and clear presentation of their synthesis. Students also practice group and individual work in this exercise.

Determining whether students have met the goals

Evaluation is based on accurate completion of calculations,testing of results, and the composition of their abstract. The abstract, in particular, shows whether students have fully grasped the concepts and understand their results.

More information about assessment tools and techniques.

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Other Materials

Supporting references/URLs

Hermoyian, C. S., L. R. Leighton, and P. Kaplan. 2002. Testing the role of competition in fossil communities using limiting similarity. Geology 30: 15-18.

Hutchinson, G. E. 1959. Homage to Santa Rosalita. American Naturalist 93: 145-159.

MacArthur, R. H. 1972. Geographical Ecology. Princeton University Press. Princeton, N.J. 269 p.

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