Download Menge and Sutherland, Amer. Nat. 110:351

Lecture 10
COMMUNITY STRUCTURE
Community Structure
Paine ‘80 - Keystone Species
Keystone species
-a relatively low biomass species that is a
major factor in determining community structure
Community Structure
Paine ‘80 - Keystone Species
Introduced concept of ‘links’ in community
e.g. Pisaster and Mytilus
Pisaster
Tonicella
Katherina
Mytilus
Lithophyllum
Hedophyllum
Community Structure
Paine ‘80 - Keystone Species
Introduced concept of ‘links’ in community
e.g. Pisaster and Mytilus
strong link
weak links
Pisaster
Tonicella
Katherina
Mytilus
Lithophyllum
Hedophyllum
Community Structure
Paine ‘80 - Keystone Species
Introduced concept of ‘links’ in community
e.g. Pisaster and Mytilus
strong link
weak links
Pisaster
Tonicella
Katherina
Mytilus
Lithophyllum
Hedophyllum
Module 1
Module 2
Keystone species
Enhydra lutris
Number of
pelts sold
1870
1880
1890
1900
Keystone species
Keystone species
Enhydra lutris
Strongylocentrotus purpuratus
Macrocystis pyrifera
But in reality - much more complex
But in reality - VERY much more complex
Another take on this - Menge and Sutherland ‘87
Rat
Food Web
Gulls
Fish
Crabs
Sea stars
Limpet
Whelk
Snails
Urchin
Red algae
Barnacles
Crusts
Bivalves
Polychaete
Emphemerals
Another take on this - Menge and Sutherland ‘87
Interaction web
Rat
Gulls
strong links
Fish
weak links
Crabs
Sea stars
Limpet
Whelk
Snails
Urchin
Red algae
Barnacles
Crusts
Bivalves
Polychaete
Emphemerals
Interactions between species in an intertidal community
Can be looked at in one of two ways
a) Hierarchy
A
A
B
C
A
C
A
B
C
B
b) Network
A
B
A
C
B
C
B
C
C
A
Time
B
A
Community Structure
Multispecies interactions - Underwood
Tesseropora - barnacle
Patelloida -acamaeid limpet
Cellana - patellid limpet
Morula - predatory whelk
Community Structure
Multispecies interactions - Underwood
Exclusion cages
Community Structure
Multispecies interactions - Underwood
Experiment 1 - Effect of Cellana on survival of Tesseropa
Morula - excluded
Tesseropora
Cellana
-grazes open rock
Community Structure
Multispecies interactions - Underwood
Experiment 1 - Effect of Cellana on survival of Tesseropa
Higher survivorship at
intermediate density
% Tesseropora
surviving
0
2
4
6
# Cellana/enclosure
8
10
Community Structure
Multispecies interactions - Underwood
Experiment 2 - Effect of Tesseropa on growth of Cellana
Cellana growth
rate
Tesseropa density
Community Structure
Multispecies interactions - Underwood
Experiment 2 - Effect of Tesseropa on growth of Cellana
Experiment 2 - Effect of Tesseropa on growth of Patelloida
Cellana growth
rate
Patelloida
growth rate
Tesseropa density
Community Structure
Multispecies interactions - Underwood
General conclusion
- major interactions among all components of system
- no keystone species - no links are ‘weak’
Community Structure
How do the forces shaping communities interact?
(Menge and Sutherland, Amer. Nat. 110:351)
Habitat
amelioration
-consider situations of
a) high and low stress
b) high and low recruitment
Relative
importance
high
low
Stress
HIGH RECRUITMENT
Community Structure
How do the forces shaping communities interact?
(Menge and Sutherland, Amer. Nat. 110:351)
Habitat
amelioration
Relative
importance
-consider situations of
a) high and low stress
b) high and low recruitment
Competition
high
low
Stress
HIGH RECRUITMENT
Community Structure
How do the forces shaping communities interact?
(Menge and Sutherland, Amer. Nat. 110:351)
Habitat
amelioration
-consider situations of
a) high and low stress
b) high and low recruitment
Predation
Relative
importance
Competition
high
low
Stress
HIGH RECRUITMENT
Community Structure
How do the forces shaping communities interact?
(Menge and Sutherland, Amer. Nat. 110:351)
Habitat
amelioration
-consider situations of
a) high and low stress
b) high and low recruitment
Predation
Relative
importance
Competition
Associational
defenses
high
low
Stress
HIGH RECRUITMENT
Community Structure
How do the forces shaping communities interact?
(Menge and Sutherland, Amer. Nat. 110:351)
-consider situations of
a) high and low stress
b) high and low recruitment
Relative
importance
Competition
high
low
Stress
LOW RECRUITMENT
Community Structure
How do the forces shaping communities interact?
(Menge and Sutherland, Amer. Nat. 110:351)
-consider situations of
a) high and low stress
b) high and low recruitment
Predation
Relative
importance
Competition
high
low
Stress
LOW RECRUITMENT
Community Structure
How do the forces shaping communities interact?
(Menge and Sutherland, Amer. Nat. 110:351)
-consider situations of
a) high and low stress
b) high and low recruitment
Predation
Relative
importance
Competition
Associational
defenses
high
low
Stress
LOW RECRUITMENT
Community Structure
How do the forces shaping communities interact?
(Menge and Sutherland, Amer. Nat. 110:351)
-consider situations of
a) high and low stress
b) high and low recruitment
Relative
importance
Predation
Habitat
amelioration
Competition
Associational
defenses
high
low
Stress
LOW RECRUITMENT
Community Structure
Relationship to diversity
Diversity
high
low
Stress
Community Structure
Relationship to diversity
Negative effects of
competition and
predation
Negative effects of
stress
Diversity
high
low
Stress
Community Structure
Disturbance and Diversity
Connell - Intermediate Disturbance Hypothesis
Diversity
Low
High
Disturbance
(frequency, intensity, extent)
Community Structure
Disturbance and Diversity
Connell - Intermediate Disturbance Hypothesis
Competitive
dominants fill
space
Diversity
Low
High
Disturbance
(frequency, intensity, extent)
Community Structure
Disturbance and Diversity
Connell - Intermediate Disturbance Hypothesis
Competitive
dominants fill
space
Few species can
invade or persist
Diversity
Low
High
Disturbance
(frequency, intensity, extent)
Models of succession
1.
Inhibition
initial colonizers inhibit future colonizers.
2. Tolerance
initial colonizers do not affect later colonizers. Organisms best suited to
local conditions will persist (e.g. Chthalamus/Semibalanus)
3. Facilitation
initial colonizers facilitate success of later colonizers (e.g. protection of
barnacles
growth of algae
Models of succession
-probably work in different areas
Habitat
stress
Recruitment
Inhibition
low
high
Tolerance
midrange
low
Facilitation
high
high or low
Community Structure:
Top-Down vs. Bottom-Up Control
Hairston, Smith and Slobodkin (1960)
Community Dynamics
Carnivores
Detritivores
control
Resource limited
Herbivores
Frees plants
from herbivore
control
Plants
Critiques
Too Simple
1) Species differences matter
2) Plant dominance could be explained by good defences
Other inferences of Hairston et al, 1960
1) Exceptions not important ??
2) All communities have 3 trophic levels
3) Omnivory not important
X
X
4) External abiotic factors - not controllers X
Robles et al, 1995
Mean
Density
(seastars/m2)
Recruitment index of Mytilus
Menge and Sutherland, 1976
Effects of predation by whelks.
Predation is weak
High wave energy - effects of predation -weak
Moderate wave energy
- effects of predation - strong
Menge
Sutherland
Ecological Relationships in Kelp Forests
Kelp
Orca
Sea Otter
Urchins
Bottom Up Control
Fretwell, 1977, 1987
- availability of plant material governs structure of food chains
- Low productivity - 1 link (plants)
- Higher productivity - add links
Transplant mussels and barnacles (filter feeders) to urchin-dominated and
kelp-dominated substrates
Transplant mussels and barnacles (filter feeders) to urchin-dominated and
kelp-dominated substrates
Expected (top down)
Urchin - dominated
Kelp - dominated
Transplant mussels and barnacles (filter feeders) to urchin-dominated and
kelp-dominated substrates
Expected (top down)
Urchin - dominated
Observed (bottom up)
Kelp - dominated
Kelp - dominated
Urchin - dominated
Clearly - can be a complex interaction
Increased nutrient
Increased algae
Increased benthic filter feeders
Increased consumers (predation)
control
Interaction of Systems
High flow
Leonard et al, 1998
Low flow
Interaction of Systems
• increased seaweed growth
• increased filter feeder growth
• increased larval settlement
• low consumer efficiency
• higher densities of
organisms with planktonic
•larvae
more spatial competition
• increased consumer pressure
• increased sedimentation
• lower densities of
organisms with planktonic
larvae
• increased consumer mortality
• less spatial competition
Leonard et al, 1998
Hydrodynamics
Flow rate
Time
Leonard et al, 1998
Community structure
High flow
Low flow
T
i
d
e
h
e
i
g
h
t
Percent cover
Percent cover
barnacles
Fucus
mussels
Bare space
Leonard et al, 1998
High flow
Recruitment rates
Barnacles
Density
(#/100 cm2)
Low flow
Mussels
Snails
Leonard et al, 1998
Crab predation
High flow
Low flow
Predation Intensity
(% mortality)
On Littorina, Nucella, Mytilus
Leonard et al, 1998
crabs
grazers
diatoms
Nutrients
mussels
Larvae
barnacles
Plankton
Leonard et al, 1998
crabs
crabs
grazers
diatoms
Nutrients
whelks
grazers
mussels
Larvae
barnacles
Plankton
mussels
barnacles
diatoms
Nutrients
Larvae
Plankton
Interference competition,
exploitative competition
for resources other than
food
(-)
Predators
(-)
(-)
Induced morphological or
chemical defenses,
hiding, retreat to refuges
Depletion of more
nutritious,
palatable or
accessible prey
- (+)
Consumers
+ (-)
Cover from (for) predators
Stimulation of areaspecific primary
productivity
Plants
(+)
Powers. ‘92. Ecology 73: 733