Center for Earth and Environmental Science
Indiana University ~ Purdue University, Indianapolis

ARBOR Project - BIRD BIODIVERSITY

 Background

            Let’s start by visiting the web page of the Union of Concerned Scientists to explore the meaning of biodiversity and why protecting biodiversity should be important to all of us. Explore some of the other links including the ones that explain the loss of  biodiversity and the protective measures that are being taken now and that might be taken in the future.

To scientists, biodiversity is a measure of the numbers of species that make up a biologic community and is considered to be one of the more important aspects of community organization and structure. The factors contributing to higher levels of diversity in some communities rather than in others are not known with certainty and remain a topic of scientific debate. Diversity appears to be partly a function of the variety of living spaces (habitats) present:  more varied habitats tend to be inhabited by a larger number of species than less variable ones. A second factor seems to be the length of time that environments have existed or have been available to organisms; older habitats usually contain more species than younger ones. Other factors that may control diversity include temperature, the presence or absence of seasons, and the stability of food supplies. Warmer, more constant, temperatures reduced seasonal differences, and stable food supplies appear to result in high levels of biodiversity. One example of how these factors interact is the latitudinal diversity gradient in shallow seas where diversity is highest at the equator and gradually decreases toward the poles.

 Terms

1. Ecology = the study of the interactions between organisms in their environment.
2. Habitat = the local environment occupied by an organism (examples = floodplain, forest, stream, lake, coral reef, etc.).
3. Population = a number of individuals of a single species occupying an area. An area may contain several species populations (see community, below).
4. Community = any group of organisms belonging to several different species that occur together in the same area (or habitat) and interact with each other (examples = feeding relationships, competition for space).
5. Ecosystem = a community of organisms and their physical environment interacting as an ecologic unit.

Measuring Biodiversity

Diversity can be measured in several different ways with a count of the number of species present representing the simplest indicator. Other measures of diversity consider the number of species present and the sizes of species populations. Most communities have one or a few abundant species (large populations) and several less abundant (even rare) species. Diversity is highest when several species are present and have similar population sizes. A count of the number of different species present in a sample is called species diversity while the measurement that reflects the different sizes of populations of species is called species evenness. Go to the Moonsnail Project’s Mini-Lecture on Diversity where you can discover how to perform diversity calculations, learn about the effect of different sample sizes on calculated values, and what the calculations mean, biologically.

Objectives

1.      To calculate species diversity and species evenness for practice data and for real research data collected (quarterly) on bird species using the floodplain of the White River at the Lilly ARBOR site.

2.      To distinguish between information provided by simple numbers of species and calculations based on the differing numbers of individuals within species.

3.      To evaluate time-related patterns (similarities or differences) detectable in these data so far. Also, are changes occurring seasonally and/or over time as the riverbank returns to its “natural” state?

Materials

1.      Practice datasheet listing species and their abundances for three samples.

2.      A calculator, or a computer with spreadsheet software, for performing calculations.

3.  Advanced students can use a statistical program, called PAST, to calculate several diversity and evenness indices.  The program is simple to use and also permits the  statistical  comparison of values calculated for single locations at different times or values for two or more geographic locations.  One can determine whether or not two diversity values are really different, statistically.  The program, a users guide, sample data sets, and sample statistical analyses can be downloaded, without cost, at the following URL:  http://folk.uio.no/ohammer/past/

Procedure

1. These terms are used by biologists (ecologists) to describe the abundance of species and individuals within an area (or environment):
   
    
   1. Species Diversity (S) - the number of species in the sample (e.g. number of bird species).
   2. Species Evenness (or equitability) - a measure of the number of individuals within species populations. Evenness is greatest when species are equally abundant.

Here is a sample data set:

2. Numerical indices are often calculated to quantitatively describe different levels of diversity and evenness in samples collected from different areas, environments, or at different times from the same environment. One example might involve an evaluation of possible biologic changes caused by modifying the environment – our interest in this exercise.  

Two commonly calculated indices are:

1. Shannon-Weaver Information Function – combines the number of species present and evenness into a single index:  D = -Σ p_i ln p_i
   
   Details:  i = an index number for each species present in a sample.
                  p_i = n_i/N = the number of individuals within a species (n_i) divided by the total
                                    number of individuals (N) present in the entire sample.
                  ln = natural log. 
   
   This means that you multiply the proportion (p_i) of each species in the sample times the natural log of that same value (ln p_i), then sum (Σ) the values for each species, and finally  multiply by minus 1.

Let’s use our sample data (5 species, 21 total individuals) and calculate D :

S = 5 species
N = 21 individuals
D = -Σ p_i ln p_i =-1 x -1.35 = 1.35

Remember:  The value of D is highest when species are equally abundant.

2. Species Evenness – separates the effect of different population sizes (numbers of individuals within species) from simple species diversity (number of species): 
       E = e^D/s
   
   Details:  e = 2.7 (= constant), D = the value of the Shannon-Weaver Information Function, and s = number of species in sample (= simple species diversity).

For our example:  E = e^D/s = 2.7^1.35/5 = 3.82/5 = 0.764

3. Using a calculator, a spreadsheet program, or PAST (click on the link and, when prompted, select Open if you're using a network PC or Save if you'd like to have a copy on your own PC), calculate both the Shannon-Weaver Information Function and Species Evenness for each of the three hypothetical environments (attached sheet). Compare the values for each paying particular attention to the distribution of individuals among species.
   
   If you decide to use PAST to perform diversity and evenness calculations, you can also  compare pairs of diversity values for statistical significance. Enter diversity data in columns, select columns by clicking on the header of the first & then holding down the shift key and selecting the second. Select Diversity indices from the Diversity Menu and the basic diversity and evenness calculations will be made. To determine whether diversity values are different statistically, select Diversity t-test from the Diversity Menu. NOTE:  Columns must be adjacent to each other for comparisons.  If they are not, simply select a column (using the header) and drag it next to the one against which you'd like to compare diversities. Select both columns and proceed as before.
4. Go to the spreadsheet containing worksheet tabs (along bottom) for the raw data, summary data, and calculations for the Shannon-Weaver Information Function and Species Evenness for bird counts collected at the ARBOR site. Examine the values and then answer the following questions:
   
    
   1. Which data collection times have the highest, and lowest, species diversities?  OPTIONAL - Using PAST, determine whether diversities are different, statistically.
   2. Are evenness values similar or different for different sampling intervals? Can you propose a reason(s) for the differences?
   3. Considering both diversity and evenness, which time interval had the most complex association of birds? Which one was least complex? 
   4. The goal of the ARBOR Project is to restore the floodplain to its original state (pre-human modification). Do calculations indicate that the Project is starting to succeed? Explain your response.

Reference Web Sites & Career Links

Species Identification Links:
            Birds of Indiana – www.ulib.iupui.edu/birds/ or www.ulib.iupui.edu/butlerbirds/
            Indiana Wildflowers - www.ulib.iupui.edu/wildflowers/
            Northern Prairie Wildlife Resource Center (Identification keys for a variety of
                    organisms) -  www.npwrc.usgs.gov/resource/resource.htm
            World Biomes –www.cotf.edu/ete/modules/msese/earthsysflr/biomes.html  

The Moonsnail Project:
                     Mini Lecture on Diversity - www.moonsnail.org/Mini_Diversity.htm

Union of Concerned Scientists:
            Definition, importance, & preservation of diversity; endangered species –
            www.ucsusa.org/environment/0biodiversity.html

Career Links:
            Careers in Biological Systematics – www.csdl.tamu.edu/FLORA/aspt/asptcar1.htm
            Careers in Biology - www.furman.edu/~snyder/careers/careerlist.html

Teacher Information Links:

Biodiversity – A collection of links on biodiversity and related topics:
www.biozone.co.nz/BIODIVERSITY.html#Biodiversity

Conservation - www.biozone.co.nz/CONSERVATION.html

Human Impact Links - www.biozone.co.nz/HUMAN_IMPACT.html 

Taxonomy  Links – www.biozone.co.nz/Biodiversity.html#Taxonomy_and_classification

The Biodiversity Center – www.defenders.org/bio-cont.html

            The Moonsnail Project - www.moonsnail.org/index.html

Reference Sources

1. Access Excellence Activities Exchange, Biodiversity Survey –

Unit Study by Jeb Schenck - www.accessexcellence.org/AE/AEC/AEF/1995/schenck_survey.html

2. Dodd, J. R. and R. J. Stanton, Jr. 1990. Paleoecology: Concepts and

Applications. John Wiley and Sons, New York.

3. Odum, E P. 1971. Fundamentals of Ecology. W. B. Saunders Company

            Philadelphia.

4. Valentine, J. W. 1973. Evolutionary paleoecology of the Marine Biosphere.

      Prentice-Hall, New York.

EVALUATING DIVERSITY                                       Name: ___________________

Required Values and Formulae:

Species Diversity = number of species in the sample.

Shannon-Weaver Information Function:  D = -Σ p_i ln p_i

Where:  i = an index for the number of species sampled, p_i = n_i/N =

percentage of species i in the entire sample (N) of individuals, and

ln = natural log.  Multiply the percentage (or proportion) of each

species in the sample times the natural log of that same value, sum

the products across all species, and then multiply by minus 1.

Species Evenness:  E = e^D/s = the distribution of individuals within species.

Where:  e = 2.7, D = value of the Shannon-Weaver information Function, and s = number of species in sample or simple species diversity.

______________________________________________________________

Ecosystem                           Species Population Sizes                                   Total No.
                                                                                                               Individuals
______________________________________________________________

     Arctic Tundra:

      14        11        9          7          98        12        15        12        16       6         200

Species Diversity = __________

Shannon-Weaver Index = __________

Evenness Index = __________

Coral Reef:

     9          7          11        12        13        14        11        9         8         10        100

Species Diversity = __________

Shannon-Weaver Index = __________

Evenness Index = __________

Temperate Forest:

      15        8          4          11        27        5          9          21        7          18        125

Species Diversity = __________

Shannon-Weaver Index = __________

Evenness Index = __________

_______________________________________________________________

Center for Earth and Environmental Science
 School of Science
 Indiana University~Purdue University, Indianapolis
 723 West Michigan Street, SL118
 Indianapolis, IN 46202
 www.cees.iupui.edu
 cees@iupui.edu