To measure the diversity in an ecosystem Simpsons Diversity Index Attempts to quantify the diversity variety of an ecosystem There are two components Evenness Richness Evenness Evenness ID: 614128
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Slide1
Simpson’s Diversity Index
To measure the diversity in an ecosystemSlide2
Simpson’s Diversity Index
Attempts to quantify the diversity (variety) of an ecosystem.
There are two components:
Evenness
RichnessSlide3
Evenness
Evenness
is a measure of the relative abundance of the different species
within an
area
. (Same amount of each kind of organism)
When the numbers of each type of species is even, the value for the Simpson Diversity Index will be larger.Slide4
Richness = variety
Richness is a measure of the number of kinds of species
More species is “richer” so the value for the index will be higher.Slide5
High Richness Native
Valdivian
Temperate RainforestSlide6
Low richness (
Pinus
Radiata
forest)Slide7
The equation
D
=
N(N
- 1
)
n
(n
-1
)
D
= diversity index
N
= total number of organisms of all species found
n
= number of individuals of a particular speciesSlide8
How to Calculate
D:
Record the numbers of each species
Calculate n-1 for each species
Find the total number of organisms, N
Calculate the Simpson Diversity Index
D =
N(N – 1)
n(n
-1)Slide9
Let’s Try an Example
You have studied a specific site, and have counted the individuals of five different species.
n
is the total number of organisms of a particular species
.
Species A
12
Species B
3
Species C
7
Species D
4
Species E
9
n
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Simpson’s Index
∑ n(n - 1) = 264
D
=
∑ n(n - 1)
N(N - 1)
Species A
12
11
132
Species B
3
2
6
Species C
7
6
42
Species D
4
3
12
Species E
9
8
72
∑ n(n - 1)
264
n - 1
n(n - 1)
n
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Simpson’s Index
D
=
∑ n(n - 1)
N(N - 1)
N - 1 = 34
N(N - 1) = 1190
N =
total number of all individuals
= 35
=
264
N(N - 1)
D
=
264
1190
=
0.22184
This area would score 0.22184 on the Simpson’s Index. The scale ranges from 0–1, with 1 representing the lowest biodiversity. Therefore, the score for this area indicates a high level of biodiversity.Page 13Teacher Zonenature.ca/educationSlide12
Calculate the Simpson’s Diversity Index for each sample
Compare the evenness and richness of each sample.Slide13
Answers
Sample One: 2.99
Sample Two: 1.15
Both have the same richness as there are three species in each area.
Sample One is more even because the numbers of each kind of species are nearly the same.Slide14
A high value of
D
suggests a stable, complex and diverse ecosystem. Slide15
A low value of
D
could suggest pollution, recent colonization or agricultural management.
Deforestation in Chile
Eukalyptus
plantationSlide16
The lowest value of D is 1.0
(
monoculture)Slide17
Compare Simpson’s Diversity Index for a tropical rainforest
vs
a desertSlide18
Biodiversity at Sites in Honduras
The following calculations are based on sampling conducted in Honduras by Canadian Museum of Nature research scientist Bob Anderson.
Site
N
N(N - 1)
∑ n(n - 1)
D
Species
Richness
Cerro Montecristo
2996
7 120 892
1 600 002
0.2247
61
El Pital 2050 m
233
54 056
6856
0.1268
22
El Pital 2650 m
5411
29 273 510
12 873 694
0.4398
46
Cerro Puca
311
96 410
19 126
0.1984
27
Santa Barbara
839
703 082
55 514
0.0789
44
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Biodiversity at Sites in Honduras
Which site has the highest species richness?
Which site is the most diverse according to the Simpson’s Index? (HINT: Has the lowest D).
Do any sites have both a low Simpson’s Index and high species richness? Which one(s)?
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