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COMMUNITY STRUCTURE EXERCISE Name
You must show your work on separate paper to get credit for the answer. Exercise 1 – Calculating Species Diversity
1. Calculate Simpson’s index and Shannon’s index for communities B and C. Fill in the table:
Community
Simpson’s index
Shannon’s index
A
4.21
1.51
B
C
2. Fill in the blank with the words indicated in parentheses following the blank.
For both indexes, greater evenness with the same richness provides a
(higher, lower, or the same) index value. (Compare A & B communities.)
When evenness is nearly identical, the community with the higher richness has a (higher, lower, the same) index value. (Compare B & C communities.)
Exercise 2 – Quantifying community similarity
1. Use Jaccard’s index to calculate the similarity between communities A and C and between communities B and C. Fill in the table:
Communities
Jaccard’s index
A & B
0.37
A & C
B & C
2. Based on these calculations, which communities are most like each other? Exercise 3 – Estimating the number of species in an area
1. Using the equation, estimate the number of species in communities B and C. Fill in the table:
Community
Number of species
A
13
B
C
2. Fill in the blank with the words indicated in parentheses following the blank:
The greater the number of species represented by a single individual, the (greater, lesser, the same) the estimated number of species in the community.
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Exercise 1: Calculating Species Diversity
Ecologists agree that communities with more species and greater evenness have higher species diversity. To quantify the species diversity of a community, we need a method of calculating a single value for species diversity. Over the years, numerous indices of species diversity have been created.Wewill consider the two that are most common and equally valid: Simpson’s index and Shannon’s index. Both indices incorporate species richness, which we abbreviate as S, and evenness. However, they do so in different ways.
To see how we calculate species diversity with either index, we can begin with data from three communities for which we have the absolute abundance for each of the species. From these data we can then calculate relative abundance for each of the five species in the community, which is denoted Pi. With these relative abundance data, we can calculate both Simpson’s index and Shannon’s index.
Table 1: The abundance of different mammal species in three communities:
Community A
Community B
Community C
Species
Absolute
abundance
Relative
abundance (pi)
Absolute
abundance
Relative
abundance (pi)
Absolute
abundance
Relative
abundance (pi)
Mouse
24
0.24
18
33
Chipmunk
16
0.16
22
33
Squirrel
8
0.08
20
33
Shrew
34
0.34
17
0
Vole
18
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