Community Ecology

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Community Ecology
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Structure of Communities

• Physical Appearance size, stratification and
  distribution
• Species Diversity number of different species
• Species Abundance the numbers of individuals of
  a species
• Niche Structure numbers of differing niches and
  how they resemble each other

3
Physical Appearance

• Types, sizes and stratification of plants and
  animals
• Mosaic of vegetation patches
• Effect of Ecotones
• Edge Effects

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Species Diversity

• Factors affecting Species Diversity
• Latitude greater diversity at equator
• Depth in aquatic systems
• Pollution

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Model of Species Diversity Island Biogeography

• 1. The number of species on an island is
  determined by the balance between immigration
  extinction.

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Island Biogeography

• 2. Small islands are expected to have lower
  immigration rates higher extinction rates,
  hence less species than large islands.
• Smaller target for immigration
• Fewer niches for immigration

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Island Biogeography

• 3. Far islands of same size are expected to have
  lower immigration rates, hence less species
  than near islands.
• Distance from mainland source of immigrants

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Island Biogeography

• large habitat patches tend to have more species
• habitat patches that are near larger intact
  habitat areas tend to have more species
• these principles can be applied to land
  preservation management efforts.

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Species Abundance

• Numbers of Organisms per unit of measure
• Impacts of Pollution
• Niche Variability
• Species Diversity
• Reproduction and Loss

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Types of Organisms

• Generalist
• Specialist

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Generalist

• Broad Niche
• Eat variety of foods
• Live in variety of habitats
• Tolerate a variety of conditions
• Example - raccoon

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Specialist

• Narrow Niche
• Eats certain foods
• Live in selected habitats
• Tolerate a narrow range of conditions
• Example - spotted owl in old growth forest

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Types of Species

• Native
• Exotic
• Indicator
• Keystone

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Native Species

• Species found in an ecosystem
• Natural organisms
• Example Brook Trout

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Exotic Species

• Species introduced
• Species migrating into ecosystem
• Species may out compete native species
• Example Killer bees, kudzu

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Indicator Species

• Species that serve as indicators that an
  ecosystem is being damaged
• Examples
• EPT
• amphibians exposed to air, land and water

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Keystone Species

• Pivotal organisms in the ecosystem
• Example Sea otters control urchins keeping them
  from depleting kelp forests

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Symbiosis

• Long-lasting relationship where species live
  together in intimate relationship
• Parasitism
• Commensalism
• Mutualism

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Parasitism

• One species is harmed other benefits
• Example Fleas, Ticks

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Commensalism

• One species benefits
• Other is not harmed
• Examples
• Vines
• Suckers on Sharks

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Mutualism

• Both species benefit
• Example
• Bacteria on Legumes

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Ecological Succession

• Complex interaction of species over time to
  colonize an area
• Two Types
• Primary
• Secondary

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Mechanisms of Succession

• facilitiation a process by which an earlier
  successional species makes the environment
  suitable for latter successional species e.g.,
  legumes fixing nitrogen can enable later
  successional species
• inhibition a process whereby one species hinders
  the establishment growth of other species
  e.g., shade of late successional trees inhibits
  the growth of early successional trees
• tolerance a process whereby later successional
  species are unaffected by earlier successional
  species.

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Primary Succession

• Establishment of biotic communities in area where
  life has not existed before bedrock.
• Pioneer Species
• Early Successional Plant Species
• Mid-successional plant species
• Late successional plant species

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Early Sucessional Plants

• Grow close to ground
• Establish large populations in short time
• Have short lives
• Condition soil for later plant growth

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Midsuccessional Plants

• Herbs, grasses and low shrubs
• Some annual and more perennial species
• Greater complexity of life cycles
• Increased soil development

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Late Successional Plants

• Diversity of trees
• Mixture of producers and decomposers
• Establishment of complex ecosystem
• Creation of niches and habitats

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Secondary Succession

• Repeat of successional progression from a
  disturbed site
• Movement of stability of the ecosystem

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Pond Succession
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Animal Succession

• Successional changes in animal community
  corresponding to changes in plant community