1. Simpson’s Diversity Index
To measure the diversity in an ecosystem

2. Simpson’s Diversity Index
Attempts to quantify the diversity (variety) of an ecosystem.
There are two components:
Evenness
Richness

3. 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.

4. 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.

5. High Richness Native Valdivian Temperate Rainforest

6. Low richness (Pinus Radiata forest)

7. The equation D = N(N - 1)  n(n -1) D = diversity index
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 species

8. How to Calculate D: D = N(N – 1)  n(n -1)
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)

9. Let’s Try an Example n
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
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10. Simpson’s Index n n - 1 n(n - 1) ∑ n(n - 1) = 264 ∑ n(n - 1) = D
Species A 12 11
132
Species B 3 2 6
Species C 7 42
Species D 4
Species E 9 8 72
∑ n(n - 1)
264
∑ n(n - 1) D =
N(N - 1)
∑ n(n - 1) = 264
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11. N = total number of all individuals = 35
Simpson’s Index
∑ n(n - 1)
264 D = =
N(N - 1)
N(N - 1)
N = total number of all individuals = 35
N - 1 = 34
N(N - 1) = 1190
264 D = =
1190
This area would score 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.
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12. Calculate the Simpson’s Diversity Index for each sample
Compare the evenness and richness of each sample.

13. 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.

14. A high value of D suggests a stable, complex and diverse ecosystem.

15. A low value of D could suggest pollution, recent colonization or agricultural management.
Eukalyptus plantation
Deforestation in Chile

16. The lowest value of D is 1.0 (monoculture)

17. Compare Simpson’s Diversity Index for a tropical rainforest vs a desert

18. 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
0.2247 61
El Pital 2050 m
233
54 056
6856
0.1268 22
El Pital 2650 m
5411
0.4398 46
Cerro Puca
311
96 410
19 126
0.1984 27
Santa Barbara
839
55 514
0.0789 44
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19. 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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