Transcript Approaches to the Study of Ecology

Community Attributes
Kenneth M. Klemow, Ph.D.
Wilkes University
Communities defined
 Assemblage of interacting populations in
an area.
 Typically categorized according to trophic
level / functional group
 Size of communities varies
 Depends on size of species and degree of
mobility
 For vegetation, concept of “stand” important
 Have important attributes
Species
composition
 List of species in an
area.
 Can range from
monocultures to
assemblages of
hundreds of species.
 Floras and faunas
www.dep.state.fl.us
Species area curve
 Look at accumulation
of species with
increasing number of
plots sampled
 Get saturation effect
 Used in conservation
biology to predict
species loss with
habitat loss
www.scieng.ed.ac.uk
Density
 Number of individuals in an area
 Each broad taxonomic group presents own
challenges
 Plants - ramets vs genets
 Animals - deal with mobility
 Fungi - What’s an individual?
 Calculate relative density
Calculating relative density
Species
A
B
C
D
E
Total
Density
Rel. Dens.
400
37.0
60
5.6
370
34.3
80
7.4
170
15.7
100.0
1080
Frequency
 Proportion of times that a species will appear
in a defined number of samples.
Species
Frequency
Total
10
Rel. Freq.
Concepts relating to frequency
 Commonness vs rarity
 Common: >60%
 Rare: <20%
 Raunkiaer’s “law”





A= 0-20%
B= 20-40%
C= 40-60%
D= 60-80%
E= 80-100%
 A>B>C=D<E
A
B
C
D
E
Abundance patterns
in communities
 Counts of species
abundance or frequencies
often yield interesting
patterns.
Spp. #
A
32
B
71
C
5
D 206
E 115
F
34
G
63
H
20
I
80
J
7
K
99
L
20
M
19
N
53
Now sort the data
 Order of decreasing
abundance
Spp. #
D 206
E 115
K
99
I
80
B
71
G
63
N
53
F
34
A
32
H
20
L
20
M
19
J
7
C
5
And categorize to yield
frequency distribution
 Place into categories of
25
Bin Freq.
Spp. #
0
0
D 206
25
5
E 115
K
99
50
2
I
80
75
3
B
71 100
2
G
63 125
1
N
53 150
0
F
34 175
0
A
32 200
0
H
20 225
1
L
20 More
0
M
19
J
7
C
5
Now create a
histogram
6
5
4
3
2
1
0
0
25
50
75
100 125 150 175 200 225 More
Bin Freq.
0
0
25
5
50
2
75
3
100
2
125
1
150
0
175
0
200
0
225
1
More
0
Now set up categories to
follow geometric
progression:









0-1
1-2
2-4
4-8
8-16
16-32
32-64
64-128
128-256
Bin Freq.
Spp. #
1
0
D 206
2
0
E 115
4
0
K
99
6
1
I
80
16
1
B
71
32
4
G
63
64
3
N
53
4
F
34 128
1
A
32 256
0
H
20 More
L
20
M
19
J
7
C
5
Bin Freq.
1
0
2
0
4
0
6
1
16
1
32
4
64
3
128
4
256
1
More
0
Now create a new
histogram
5
4
3
2
1
0
1
2
4
6
16
32
64
128
256 More
Ecologists have found lognormal
distribution in nature
Diversity
 Measure of
heterogeneity among
species in a community
 Has two components:
 Richness
 Evenness
www.ipgri.cgiar.org
Measures of Diversity
 Species richness - S
 Shannon-Weiner index
 H’ = -(pi x ln pi)
 Accounts for both richness and evenness
 Evenness
 J = H’/ln S
 Simpson’s index
 (pi)
 Accounts for dominance
 Inverse Simpson’s index
 1/ (pi)
 Accounts for diversity
Look more closely at ShannonWeiner index
Stress-subsidy relationships
important
H’
Stress
Subsidy
 diversity
  diversity - within specific community or
habitat
  diversity - across several communities
along a gradient
  diversity - across range of habitats in
landscape or geographic area
Dominance
 Degree to which one
species intercepts
resources and regulates
community function
 Typically related to
biomass
 Concept of keystone
species
geoggeol.wku.edu
Stability
 Ability of a community
to remain constant over
time, especially in face
of perturbation.
 Two components:
 Resistance
 Resilience
www.epa.gov/nps/