Community Ecology

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Chapter 54

• Community Ecology

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Community Ecology

• The study of the interactions between the species
  in an area.

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Interspecific Interactions

• Interaction between species.
• May be positive, negative, or neutral (in regards
  to fitness)
• Ex
• Predation
• Mimicry
• Competition
• Symbiosis

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Predation (/-)

• Predator and prey relationships.
• Ex Lynx and Hares

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Herbivory (/-)

• When an organism eats parts of a plant or algae.
• Herbivore may have special adaptations to find
  their prey.
• Plants may have adaptations to avoid being
  eaten.

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Predation/Herbivory

• Often results in interesting defenses or
  adaptations.
• Ex
• Cryptic coloration
• Aposematic coloration

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Cryptic Coloration

• A passive defense where the prey is camouflaged
  against its environment.

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Aposematic Coloration

• The use of conspicuous colors in toxic or
  unpalatable organisms to warn off predators.

• poison arrow frogs

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Mimicry

• Defense mechanism where the mimic has a
  resemblance to another species, the model.
• Types
• Batesian
• Müllerian

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Batesian Mimicry

• Palatable species mimics an unpalatable model.

Hawk moth larva
Snake
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Müllerian Mimicry

• Two unpalatable species resemble each other.

Yellow Jacket
Cuckoo Bee
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Competition

• When two species rely on the same limiting
  resource.
• Intraspecific competition usually more severe
  than Interspecific competition.
• Why?

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Competitive Exclusion Principle

• Predicts that two species with the same exact
  requirement cannot co-exist in the same
  community.
• The better adapted species will survive and the
  less adapted will go extinct.

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Think, Pair, Share

• Discuss if the Competitive Exclusion Principle
  explain the spacing of fast food restaurants on
  the strip in most towns.

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Ecological Niche

• The sum of a species use of the biotic and
  abiotic resources in its environment is called
  the species ecological niche.
• How a species makes its living in its
  ecosystem.
• Species can not have niche overlap, the
  Competitive Exclusion
  Principle

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Niche Types

• 1. Fundamental - what a species is theoretically
  capable of using.
• 2. Realized - what a species can actually use.

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Think, Pair, Share

• Again in terms of fast food restaurants, explain
  the concept of a fundamental vs. realized niche.

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Resource Partitioning

• A way that species avoid niche overlap by
  splitting up the available resources.
• Ex Anolis lizards

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• A. distichus

• A. insolitus

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Symbiosis

• When two different species live together in
  direct contact.
• Types
• 1. Parasitism
• 2. Commensalism
• 3. Mutualism

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Parasitism (/-)

• Parasite harms the host.
• Parasites may be external or internal.
• Well adapted parasites don't kill the host.
• https//www.youtube.com/watch?vuvdiYg6ZN-U
  Sci-Show Parasites

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Commensalism (/o)

• One partner benefits while the other is
  unchanged.
• Ex. Cattle and Egrets

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Mutualism (/)

• Both partners benefit from the interaction.
• Ex Pollinators and flowers

Acacia Tree and Ants
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Species with large impacts

• Some species have larger impacts on a community
  structure than others.
• Ex
• Dominant Species
• Keystone Species
• Foundation Species

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Dominant Species

• A species that is the most abundant or has the
  highest biomass in a community.
• Has a major effect on a community both biotically
  and abiotically.

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Reason for Dominance?

• Best Competitor?
• Best in avoiding predators and disease?
• Invasive species may fit the last explanation.

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Example

• Chestnuts used to make up to 40 of the forest.
• Lost between 1910-1950 because of fungus disease.
• Major impact on wood and nut industries.

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Response

• Some tree species increased in abundance to fill
  the gap.
• Mammals and birds did OK.
• 7 species of insects went extinct.

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Keystone Species

• Not a dominant species, but has a major impact in
  the community structure.
• Often a top predator that controls the numbers of
  other species.
• Ex. Sea Otters

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Foundation Species

• Species that cause physical changes in the
  environment that affect others.
• Ex. Beavers, Bison, Black Rush

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• https//www.youtube.com/watch?vysa5OBhXz-Q
• How wolves change rivers

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Succession

• Changes in species composition over time.

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Succession Stages

• Climax Community - An ecological community in whic
  h populations of plants or animals remain
  stable and exist in balance  with each other and 
  their environment.

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Succession Types

• 1. Primary
• 2. Secondary

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Primary Succession

• Succession with only abiotic materials as the
  starting substrate
• Ex volcanic islands glaciated areas
  road cuts

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Secondary Succession

• Succession with biotic materials (living or dead)
  as the starting substrate
• Ex
• Cutting down a forest
• Forest fire
• Tornado/storm damage

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Steps of Succession

• Pioneer Species the first organisms to appear
  in the area in primary succession
• Usually moss or lichens

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What do Pioneer Species Change?

• Enrich the soil as generations die, their
  remains decompose and add nutrients to the soil
  (often N).
• The soil is now able to support a greater variety
  of species such as grasses and small shrubs.

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• Which occurs faster, primary or secondary
  succession?
• What can you do to speed up succession?

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Point

• If you understand the causes and controlling
  factors of succession, you can manipulate them.

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Some points about Succession

• The Organisms are changing in the area over time.
  General pattern is an increase in biodiversity.
• The Climate of the area is NOT changing over time.

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Other Changes

• Soil becomes richer in N, more depth, better
  water retention etc.
• Light can decrease at ground level because of
  shading by taller plants.

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Summary

• Know the various types of interspecific
  interactions.
• Know the Competitive Exclusion Principle and
  Niche Concept.
• Know Species with large impacts.

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Summary

• Know some examples and causes of succession.