Simpson's Diversity Index
Studying Biodiversity
Background:
The Simpson's Diversity Index is a mathematical formula that takes into
account species richness and evenness. The value of this index starts with 1
as the lowest possible figure. This figure would represent a community
containing only one species. The higher the value, the greater the diversity.
The diversity index (D) is calculated as:
D = N(N-1)/sum ni(ni-1)
Where:
N = total number of organisms in the survey
ni = the number of individuals for each species
Data Table:
Midlothian Middle School,
Chesterfield Co., Virginia
Forest Community, Mountain
Lake, Virginia
Forest Community,
Narrows, Virginia
Species
# of trees
Species
# of
trees
Species
# of
trees
Mockernut Hickory
10
Red Oak
8
Sycamore
2
Shagbark Hickory
1
Red Maple
2
Green Ash
1
Post Oak
1
Eastern Hemlock
2
Black Walnut
1
White Oak
7
Striped Maple
4
Persimmon
1
Scarlet Oak
1
Sugar Maple
1
Honeylocust
1
Black Oak
1
Sweet Birch
1
Black Willow
1
Southern Red Oak
1
.
.
Boxelder
1
Sweetgum
2
.
.
Slippery Elm
1
American Holly
1
.
.
Flowering Pear
1
.
.
.
.
Crab Apple
1
N
.
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.
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Analysis:
1. How many species of tree grew at each of the locations?



Chesterfield Co. __________
Mountain Lake __________
Narrows __________
2. If diversity were just a measure of numbers of species, which location
would be the most diverse?
3. How many individual trees grew at each location?



Chesterfield Co. __________
Mountain Lake __________
Narrows __________
4. If the diversity were just a measure of number of trees, which location
would be the most diverse?
5. Which forest community had the most even distribution of trees?
6. What is the best indicator of diversity, the number of species, the
number of individuals, the evenness, or a combination of all three indicators?
7. At this point, which forest community do you think is the most diverse?
Explain how you reached this conclusion.
8. Calculate the Simpson's Diversity Index for Chesterfield County. Show
your work!
9. Calculate the Simpson's Diversity Index for Mountain Lake. Show your
work!
10. Calculate the Simpson's Diversity Index for Narrows. Show your work!
11. Using the Simpson's Diversity Index, which community is the most
diverse?