Name: Key
Directions: Visit the following website and use this as a resource to help you answer the questions that follow. Place
your completed document in my inbox when you are finished. (The file title should have your “class section, last name
and the word index” in it.)
http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/bio%20206/206%20laboratory/species%20diversity/spec
ies_diversity.htm
1. What is the difference between species evenness and species richness? The number of species in a community is the
species richness and the relative abundance of rare and common species is called the species evenness.
2. How do the evenness and richness of a species tie into the diversity? includes both species richness and evenness.
Communities with a large number of species that are evenly distributed are the most diverse and communities with
few species that are dominated by one species are the least diverse.
3. How was the Simpson index derived? If a community with high diversity was randomly-sampled twice, there is a
good chance that the two samples will contain different species. However, if a low-diversity community were
sampled twice, it is likely that both of the samples will contain many of the same species. Simpson (1949) derived a
formula based on the expected outcome of two random samples.
4. In what case would we use the Shannon-Weiner index? The Shannon-Weiner index was developed from
information theory and is based on measuring uncertainty. The degree of uncertainty of predicting the species of a
random sample is related to the diversity of a community. If a community is dominated by one species (low diversity),
the uncertainty of prediction is low; a randomly-sampled species is most likely going to be the dominant species.
However, if diversity is high, uncertainty is high.
Exercise
1. Use Simpson's index (equation 1) to calculate species diversity for the three communities shown in the
table below. Show your work for Community A. It is not necessary to show your work for Communities B and
C.
Species
Number of Individuals
Community A Community B Community C
1
46
10
25
2
1
10
25
3
1
10
0
4
1
10
0
5
1
10
0
Total
50
50
50
N(N-1)
Ds = ______
ni(ni-1)
Equation 1
where N = the total number of individuals of all species
ni = the number of individuals of species i
A.
50 X 49
2450
Ds =
___________________________
= ____ = 1.18
(46 X 45) + (1 X 0) + (1 X 0) + (1 X 0) + (1 X 0) 2070
B.
Ds =
50 X 49
2450
___________________________
= ____ = 5.45
(10 X 9) + (10 X 9) + (10 X 9) + (10 X 9) + (10 X 9)
450
C.
50 X 49
2450
Ds =
___________________________
= ____ = 2.04
(25 X 24) + (25 X 24) + (0 X 0) + (0 X 0) + (0 X 0) 1200
2. Use the Shannon-Weiner index to calculate species diversity for the three communities shown in the table
above. Use either equation 2 or equation 3. Equation 3 is easier. Show your work for Community A. It is not
necessary to show your work for Communities B and C.
H' = -
pi ln pi
Equation 2
Where pi = the proportion of individuals of species i.
N ln N - (ni ln ni)
H' = ________________
N
Equation 3
3. Do the two methods of calculating species diversity (questions #1 and 2 above) give you the same answer?
Do they show the same pattern?
4. Communities A and B each have the same species richness (5 species each). Which has the highest species
diversity?
Why?
5. Communities B and C both have high evenness. Which has the highest species diversity?
Why?