Download 53 Community Ecology

Chapter 53:
Community Ecology
Community Ecology
 The study of the interactions between the
species in an area.
Community Hypothesis
1. Individualistic
 H.A. Gleason
 Community as a chance assemblage of
species because of similar abiotic
requirements.
2. Interactive
 F.E. Clements
 Community as a linked assemblage of
species that function as an integrated whole.
Predictions
 Individualistic - fuzzy borders
 Interactive - sharp borders
 Robert Whittaker – tested the two ideas
against each other.
Results
 If abiotic factors form a continuum, then
borders are fuzzy.
 Individualistic Hypothesis is correct.
 Comment


Abiotic factors may form sharp borders.
Ex: soil types
 Result – the Community may look very much
like the Interactive Hypothesis.
Interspecific Interactions
 Interaction between species.
 May be positive, negative, or neutral.
 Ex:
1. Coevolution
2. Predation
3. Mimicry
4. Competition
5. Symbiosis
Coevolution
 When two species have
reciprocal evolution to each
other.
 Ex:
 Flowers and their
pollinators.
Predation (+/-)
 Predator and prey
relationships.
 Ex – Lynx and Hares
 Often results in
interesting defenses or
adaptations.
 Ex:



Plant defenses
Cryptic coloration
Aposematic coloration
Cryptic Coloration
 A passive defense where the prey is
camouflaged against its environment.
Aposematic Coloration
 The use of conspicuous
colors in toxic or
unpalatable organisms
to warn off predators.
poison arrow frogs
Mimicry
 Defense mechanism where the mimic has a
resemblance to another species, the model.
 Types:


Batesian
Mullerian
Batesian Mimicry
 Palatable species mimics an unpalatable
model.
Hawk moth larva
Snake
Mullerian Mimicry
 Two unpalatable species resemble each
other.
Cuckoo Bee
Yellow Jacket
Competition
 When two species rely on the same limiting resource.
 Intraspecific competition usually more severe than
Interspecific competition.
 Why?
 Competitive Exclusion Principle


Predicts that two species with the same requirement
can not co-exist in the same community.
One species will survive and the second will go extinct.
Ecological Niche
 The n-hyperspace of requirements for a species.
 How a species “fits into” an ecosystem.
 Species can not have niche overlap, the
Competitive Exclusion Principle
 Niche Types
1. Fundamental - what a species is theoretically
capable of using.
2. Realized - what a species can actually use.
Resource Partitioning
 A way that species avoid niche overlap by
splitting up the available resources.
 Ex: Anolis lizards
A. distichus
A. insolitus
Symbiosis
 When two different species live together in
direct contact.
 Types:
1. Parasitism
2. Commensalism
3. Mutualism
Parasitism (+/-)
 Parasite harms the host.
 Parasites may be external or internal.
 Well adapted parasites don't kill the host.
Parasitic behavior: A female Nasonia vitripennis laying a
clutch of eggs into the pupa of a blowfly (Phormia regina)
Commensalism (+/o)
 One partner benefits
while the other is
unchanged.
 Ex. – Cattle and Egrets
Mutualism (+/+)
 Both partners benefit
from the interaction.
 Ex: Pollinators and
flowers
Acacia Tree and Ants
Succession
 Changes in species
composition over time.
Succession Stages
 Sere: unstable stage usually replaced by
another community.
 Climax: stable stage, self-reproducing.
 Succession Types:
1.
2.
1. Primary
2. Secondary
Primary Succession
1.




Primary
Building a community from a lifeless area.
Ex: volcanic islands
glaciated areas
road cuts
The first example of primary succession was
worked out on the Indiana Dunes.
Stages:




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Open Beach
Beach Grasses
Conifers (Junipers and Pines)
Oaks
Beech-Maple forest (Climax)
Secondary Succession
 Where a community has been disturbed and
the soil is mostly intact.
 Ex:


Cutting down a forest
Blow-outs on the Dunes
Causes of Succession
1. Autogenic Factors
 Changes introduced by the organisms
themselves.
 Ex: toxins
acids
2. Allogenic Factors
 Outside disturbances
 Ex: Fire
Floods
Prairie Restoration Project
Upland, IN
Biogeography
 Study of the past and present distributions of
individual species and communities.
 Range Limitations
1. Lack of dispersion.
2. Failure to survive in new areas.
3. Retraction from former range area.
 Proof



Fossil Evidence
Pollen Studies
Transplant Experiments
Islands
 Special cases in Biogeography.
 Must be colonized from other areas.
 Island Species Factors


Island size.
Distance from mainland.
Island Size and Distance
 Small islands hold few species.
 Why?

Fewer niches available for species to occupy.
 Distance from Mainland

Closer islands have more species.
 Why?

Easier for colonization.
Comment
 Islands tend to have high numbers of
Endemic species
 Why?
 Adaptive Radiation and Evolution of new
species.
Summary
 Know the two hypothesis of community
structure.
 Know the various types of interspecific
interactions.
 Know the Competitive Exclusion Principle and
Niche Concept.
 Know some examples and causes of
succession.
 Know how island communities are shaped.