APES Lab: Diversity Lab
Essential Question:
How is the Shannon-Wiener Index and Simpson’s index used to measure diversity in
an ecosystem?
Background Information
A central theme in ecology is biodiversity, which often serves as a measure of the overall health
of an ecosystem. Declining biodiversity can indicate that the ecosystem is undergoing some type
of environmental stress. Further study may then help to pinpoint that stress. Quantifying the
species diversity of ecological communities can be complicated. In addition to issues of
statistical sampling, the rather arbitrary nature of delineating an ecological community, and the
difficulty of positively identifying all of the species present, species diversity itself has two
separate components: 1) the number of species present (species richness) and 2) their relative
abundances (evenness).
Richness - a measure of the number of different kinds of organisms present in a
particular area. For example, species richness is the total number of different species
present in a community. Some communities may be simple enough to allow complete
species counts to determine species richness. However, this is often impossible,
especially when dealing with insects and other invertebrates, in which case some form
of sampling has to be used to estimate species richness.
Evenness - a measure of the relative abundance of the different species making up the
richness of an area. To give an example, we might have sampled two different fields
for wildflowers. Both samples have the same number of species (3) and the same total
number of individuals (1000). The total number of individuals in sample 1 is quite
evenly distributed between the three species. In the second sample, most of the
individuals are buttercups, with only a few daisies and dandelions present. Sample 2
is therefore considered to be less diverse than sample 1.
Flower Species
Daisy
Dandelion
Buttercup
Total
Table 1: Flowers
Numbers of individuals
Sample 1
Sample 2
300
20
335
49
365
931
1000
1000
As a result, many different measures of biodiversity have been developed. Here, we will explore
two measures of biodiversity: The Shannon-Wiener Index (H’) and the Simpson Index (D)
Shannon-Wiener Index
The Shannon-Wiener Diversity Index is a common way of showing that diversity involves not
only numbers of different species, but also how well each of these species is represented in
different “habitats.” It is calculated the following way:
ni
pi = N
(equation 1)
H' = –
S
 pi (ln (pi))
i=1
(equation 2)
ni = number of individuals of species "i"
N = total number of individuals of all species
pi = relative abundance of species "i" (see equation 1)
S = total number of species
H' = The Shannon Diversity Index (see equation 2)
Interpretation: The Shannon-Wiener value “H” can range from no diversity at 0.0 (think of a
Christmas Tree farm) to a maximum diversity of 4.0 (think of a rainforest). These values have
no real meaning by themselves, but can be used to compare two communities or the same
community at different times. Typical values are generally between 1.5 and 3.5 in most
ecological studies, and the index is rarely greater than 4. The Shannon index increases as both
the richness and the evenness of the community increase. The fact that the index incorporates
both components of biodiversity can be seen as both strength and a weakness. It is a strength
because it provides a simple, synthetic summary, but it is a weakness because it makes it difficult
to compare communities that greatly differ in richness.
Due to the confounding of richness and evenness in the Shannon index, many biodiversity
researchers prefer to stick to two numbers for comparative studies, combing a direct estimate of
species richness (the total number of species in the community, S) with some measure of
dominance or evenness. The most common dominance measure is Simpson’s index.
Shannon-Wiener Example
The Shannon-Wiener equation is: H’ = - sum(pilnpi)
pi =
ni
N
pi = the ratio of the number of organisms of a species to the total number of organisms
ni= number of individuals in species “i”
N= total number of individuals of all species
lnpi = the natural log of pi (use the LN button on your calculator)
**Note there is a negative sign before the sum sign, which means that your answers will always
be positive.
Shannon-Wiener Example Data Set
Parking Lot A:
Species of Car
Species Identifier Number of Individuals
Code
in Parking Lot A
I
ni
pi
ln(pi)
pi (ln(pi))
Sedan (4-door or 2-door with regular
trunk)
1
10
0.17
-1.77196
-0.30123
SUV (higher off ground, gate in back)
2
10
0.17
-1.77196
-0.30123
Van or Mini-Van (sliding doors with
hatch in back)
Pick-Up Truck (cargo in back)
3
10
0.17
-1.77196
-0.30123
4
10
0.17
-1.77196
-0.30123
Station Wagon or Hatchback
5
10
0.17
-1.77196
-0.30123
Bikes or Motorcycles
6
10
0.17
-1.77196
-0.30123
S=6
N=60
1
TOTAL
-1.8074
Therefore H’=1.8074
Parking Lot B:
Species of Car
Species Identifier Number of Individuals
Code
in Parking Lot B
I
ni
pi
ln(pi)
pi (ln(pi))
Sedan (4-door or 2-door with regular
trunk)
1
1
0.02
-4.09434
-0.06824
SUV (higher off ground, gate in back)
2
2
0.03
-3.4012
-0.11337
Van or Mini-Van (sliding doors with
hatch in back)
Pick-Up Truck (cargo in back)
3
25
0.42
-0.87547
-0.36478
4
32
0.53
-0.62861
-0.33526
Station Wagon or Hatchback
5
0
0
0
0
6
0
0
0
S=4
N=60
1
Bikes or Motorcycles
TOTAL
0
-0.88165
Therefore H’= 0.88165

Which parking lot above is more diverse? Lot A (S=6, H’=1.8074). The car species are equally
represented in this lot. We say that this parking lot (community) has a high degree of evenness. Lot B is
less diverse based on our indexes (S=4, H’=0.88165) and has low evenness, because the car species are
unequally represented. Chevy Cavaliers are the most common species in Lot B, followed by Toyota
Corollas. This lot has a high degree of dominance by these two species (p3+p4=.95=95% of the
individuals in this parking lot are Chevy’s and Toyotas).
Diversity Measurement
Species richness (S)
Evenness
Dominance
Overall Diversity
Shannon Diversity Index (H’)
Community A (Lot A)
Community B (Lot B)
6 species
High
Low
High
1.8074
4 species
Low
High
Low
0.88165
Simpson’s Index
Simpson’s Diversity Index is a measure of diversity, which takes into account the number of
species present, as well as the relative abundance of each species. As species richness and
evenness increases, so diversity increases.
D = dominance
n = the total number of organisms of a particular species
N = the total number of organisms of ALL species
Interpretation: As dominance (D) increases, diversity (in the sense of evenness) decreases.
As an example, let us work out the value of D for a single quadrat sample of ground vegetation
in woodland. Of course, sampling only one quadrat would not give you a reliable estimate of the
diversity of the ground flora in the wood. Several samples would have to be taken and the data
pooled to give a better estimate of overall diversity.
Species
Number (n)
n(n-1)
Woodrush
2
2
Holly (seedlings)
8
56
Bramble
1
0
Yorkshire Fog
1
0
Sedge
3
6
Total (N)
15
.
.
n(n-1)
64
Putting the figures into the formula for Simpson's Index
D = 1 - (64)
15 (14)
D = 1- (64)
210
D = 1 - 0.3
D = 0.7
The value of D ranges between 1 and 0, with 1 being the most diverse and 0 the least diverse.
Materials:
 Vehicles parked at the school
 Calculator
Procedure:
Your team will count the vehicles in the right area of parking and the vehicles in the left area of
the parking lot. For species, you will record the make of the cars. Create charts in your
notebook to record your data.
Now collect data.
Shannon-Wiener Index Data Tables
Right Side Parking Lot Area (Community A)
Species
Identifier
Species of Car (make of car)
Code
I
1
2
3
4
5
6
7
TOTAL
Left Side Parking Lot Area (Community B)
Species
Identifier
Species of Car (make of car)
Code
I
1
2
3
4
5
6
7
TOTAL
Number of Individuals in Parking Lot A
ni
pi
ln(pi)
pi (ln(pi))
pi
ln(pi)
pi (ln(pi))
Number of Individuals in Parking Lot B
ni
Simpson Index Data Table – Community A
n = the total number of organisms of a particular species
N = the total number of organisms of all species
Species (make of car)
Number (n)
Example: Jeep
Example: 6
n(n-1)
Example: 6(6-1) = 30
Simpson Index Data Table – Community B
n = the total number of organisms of a particular species
N = the total number of organisms of all species
Species (make of car)
Number (n)
Example: Jeep
Example: 6
n(n-1)
Example: 6(6-1) = 30
Fill in the following chart and use for your analysis:
Diversity Measurement
Community A
Community B
Species richness (S)
Evenness
Dominance
Overall Diversity
Simpson Diversity Index (D)
Shannon-Wiener Diversity Index
(H’)
Analysis:
1. Compare the two parking lot samples and the diversity indexes. Why might ecologists use two
different indexes for comparative studies?
2. Which species are more dominant in each community? Why do you think this is the case?
3. Which group, if any, is more diverse? Why do you think this is the case?
4. If you conducted this lab in a shopping mall parking lot, predict whether the diversity index would be
high or low, and how it would compare to the school parking lots.
5. If you conducted this lab at a new car dealership, predict whether the diversity index would be high
or low, and how it would compare to the school parking lots.