Chapter 1
What is Biodiversity?
Spiders as Exemplars of the
Biodiversity Concept
Five forest remnants from a previously
contiguous forest.
How was the spider
community sampled?
Are there other
spiders present that
weren’t collected?
Cumulative number of species
Have you sampled enough?
The Collector’s Curve
Summary Table
Sites
Species
1
2
3
4
5
6
Etc.
Total specimens
Total Species
1
2
3
4
5
Total
Analyzing Community Diversity
Simpson Reciprocal Index, 1/D
[Erratum: page 8, line 3; 2s are exponents]
D =  pi2
where pi is the fractional abundance of each species
Sometimes referred to as “evenness”
For Site 1
There are 10 species, each with 5 specimens
D =  pi2
Where pi is the fractional abundance of each species
1/D = 1/[ (5/50)2 + +(0.1)2 +(0.1)2 +(0.1)2 +(0.1)2 +(0.1)2 +(0.1)2 +(0.1)2 +(0.1)2 +(0.1)2]
1/D = 10
The higher the value, the more diverse. The maximum value is the number of
species present. This indicates an equal number of individuals in each species.
Analyzing Community Distinctiveness
Jaccard Coeffecient of Community Similarity, CCJ
CCJ = c /S
Where
c is the # of species common to both communities
S is the total # of species in both communities
Value ranges from 0 to 1:
0 indicates no species in common
1 indicates all species found in both communities
CCj estimates
Site
1
2
3
4
5
Mean
1
2
3
X 0.33 0.33
0.33 X
1
0.33 1
X
0
0
0
0
0
0
4
5
0
0
0
X
0
0
0
0
0
X
0.165 0.333 0.333 0.000 0.000
For Sites 1 and 2
CCJ = c /S
= 4 common/12 total
= 0.333