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Bio122, Fall 2015 Activity #6 (10/22/15): Communities
Name__________________________
I. Using Biodiversity Indices
 A diversity index is a mathematical measure of species diversity in a given community.
 These indices are based on the species richness (the number of species present) and
species abundance (the number of individuals per species).
 The most commonly used is the Shannon Index (H) = - Σpi ln pi where:
 p is the proportion (n/N) of individuals of one particular species found (n) divided by the total
number of individuals found (N)
 In is the natural log
 Σ is the sum of the calculations (calculate for each species, then sum them all)
 A higher value of H indicates higher diversity.
The Shannon index is an information statistic index, which means it assumes that all species are
represented in a sample and that they are randomly sampled.
1. What problems might arise using these assumptions?
Look at the following tables of insects in two different fields.
2. Create a species abundance curve for each (on the same graph) in the space below:
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2. Fill out the following tables and calculate H for each field.
Field A:
Order
Orthoptera
(grasshopper)
Orthoptera
(grasshopper)
Lepidoptera
(butterfly)
Lepidoptera
(butterfly)
Coleoptera
(beetle)
Description
Green with
red legs
Brown w/
yellow stripe
Large, blue
#
n/N =
individuals pi
(n)
6
Ln pi
5
1
Small, blue
3
Red & blue
12
N=
Σpi=
Σpi ln pi =
H = - Σpi ln pi
=
Species
richness =
Field B:
Order
Hymenoptera
(wasp)
Hymenoptera
(wasp)
Hymenoptera
(bee)
Orthoptera
(grasshopper)
Lepidoptera
(butterfly)
Lepidoptera
(butterfly)
pi lnpi
Description
black
#
n/N =
individuals pi
(n)
12
purple
21
striped
25
Brown w/
yellow stripe
Large, blue
2
Small, blue
9
Ln pi
pi lnpi
17
N=
Species
richness =
3. Which field has greater species evenness?
4. Which field is more diverse (has a bigger index)?
Σpi ln pi =
H = - Σpi ln pi
=
3
5. Examine the data from the following table of species diversity of marine organisms in Norway (Gray
2000).
a. Is the richest site also the most diverse?
b. Is the order from least to most diverse the same as the order of least to most species rich?
c. How can you reconcile the difference in rank order of richness and diversity?