This experiment illustrates how ecological theory can help conserve native species in a fragmented landscape. It is germane to units on biogeography, human impacts on ecosystems, landscape ecology, conservation, and restoration. During the first lab, the instructor introduces the process of habitat fragmentation, the degree to which species in species-poor assemblages are proper subsets of species-rich assemblages (i.e., degree of nestedness), the possible relationships between fragmentation and nestedness, and identification of common breeding bird species in regional forest fragments. Between the first two labs, students practice bird identification, read about the general effects of fragmentation on bird populations and communities, and consider whether bird assemblages might be nested by specific attributes of habitat fragments. During subsequent labs and out of class time, student groups survey breeding birds in forest fragments, perform a statistical analysis, and assess the relative merits of the alternative hypotheses. Student groups complete the experiment by presenting scientific research posters.
Four lab periods (minimum of 3 hours each) and one lecture period.
OUTSIDE OF CLASS TIME
Ten hours per student, based on the following: 2 hours to read in preparation for lab periods one and two, 3 hours for practice identifying organisms, 3 hours for data processing and analysis, and 2 hours to generate products for submission.
A short report with alternative hypotheses and associated rationales, spreadsheets with fragment attribute data and field survey data, a short report with statistical and graphical analysis of the field survey data, oral discussion of results, and a scientific research poster.
9 to 12 native habitat fragments varying in area and isolation.
I use this experiment in a 400-level general ecology course for biology majors at Oglethorpe University. A typical course section has around 9 students. I divide the section into three groups that work independently.
Oglethorpe University is a small private liberal arts institution with a largely undergraduate enrollment. It is located in a suburb of Atlanta, GA.
This experiment can be transferred to other mid- to upper-level courses for science majors (conservation biology, landscape ecology, and environmental science), larger lab sections, other taxa, and other ecosystems. It is not appropriate for students with significant physical disabilities and is not easily scheduled outside of late spring/early summer if breeding birds are used.
A few years back, I wanted to test whether assemblages were nested by attributes of habitat fragments. Direct statistical tests were only performed by a handful of people, including Erica Fleishman (Stanford University and National Center for Ecological Analysis and Synthesis). Erica was helpful, knowledgeable, and supportive regarding these tests, so we talked a great deal about nestedness and its potential to inform conservation planning. With the able support of John Fay (Stanford University and Duke University) and Rick Reeves (National Center for Ecological Analysis and Synthesis), we updated the format of the existing statistical tests so that they functioned on common computing platforms and published a manuscript on nestedness analyses and conservation planning. Bruce Patterson (Field Museum of Natural History) and Wirt Atmar (AICS Research) graciously provided historical context, encouragement, editorial assistance, and humor throughout the production of the manuscript. While the manuscript was in review, I designed this experiment in the hopes of engaging more students with problem-based and active learning. This idea would not have occurred to me but for my exceptional mentors from the University of Washington: Elizabeth Feetham, Marsha Landolt, and John Marzluff. Two TIEE reviewers and an associate editor provided extremely helpful comments on a draft of this exercise.
Roarke Donnelly. Febraury 23 2009, posting date. An Assessment of Assemblage Nestedness in Habitat Fragments. Teaching Issues and Experiments in Ecology, Vol. 6: Experiment #5 [online]. http://tiee.ecoed.net/vol/v6/experiment/assessment_assemblage/abstract.html
These Matryoshka dolls represent a set of perfectly nested assemblages if one assumes (a) each doll represents an assemblage, (b) doll size is positively correlated with species richness, and (c) and physical nesting of a smaller doll within a larger doll indicates that all the species in the species-poor assemblage are found within the species-rich assemblage.