Species Interactions

Community ecology (topics)
• Species diversity [2]
• Island Biogeography [4]
• Niches [5]
• Species Interactions [6]

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Species diversity

What determines the number of species in a community?
• Where is diversity greatest ?
• What determines diversity on islands?

Where is diversity greatest?

The Tropics
Why?
• Greater rates of Speciation
  1. more resources (= larger pop'ns. & more niches)
  2. positive feedback (sp. interactions)
• Lower Rates of Extinction
  1. Greater stability

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What determines species diversity on islands?
• Rates of Immigration vs. Extinction
  • Immigration rate = proximity to "mainland"
  • Extinction rate = size of island

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Niches:
the roles species play in communities

• Indicator species
  e.g., pincushion cactus
• Keystone species
  e.g., cougar link
• Exotic species
  • Bermuda grass +
  • Buffel Grass & Fg
  • Tamarisk Tamarix
  • Africanized bees
  • Zebra Mussels

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"Styles" species interact

• Competition (-1, -1) (-1, 0)
• Predation (-1, +1)
• Parasitism (-1, +1)
• Mutualism (+1, +1) 1 2
• Commensalism (0, +1) 1 2

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Competition (-1, -1) (-1, 0)

• intraspecific (within species): territoriality + +
• interspecific (between species): Interference .
  • niche partitioning warblers shore birds
  • character displacement
    (e.g., Darwin's finches)
    fig + [+] [+] [.]

Predation (-1, +1)

• Predators
  • pursuit
  • ambush
• Prey +
  • avoidance *citation
  • toxicity
  • mimicry

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