Species Interactions and Community structure

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Species Interactions and Community structure

• Chapter 17 Ecology

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Food Chains vs. Food Webs
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A Food Chain in the Rocky Tidal Pools
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Tide Pool Food Chain Players primary producers

• Algae at the base of the food chain
• Attached to rocks
• Porphyra and Corallina are two common species

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Filter feeders

• Balanus the barnacle
• Attached to rocks and
• Sessile

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Motile guys

• Katharina tunicata, a chiton
• Herbivore
• Roams around on rocks scraping algae like a
  wanderin dillo of the tide pool

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Another motile guy

• Nucella
• Also motile like chitons, but
• they eat barnacles

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Our Star Pisaster

• Top predator (top of the food chain)
• Roams (slowly) around rocks ripping open molluscs
  and chowing down on them.

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So what happens when we remove Pisaster, our top
predator?

• Lets see a model simulation
• Results of an actual experiment (not a model)

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The results were transferable to s similar
tidepool in New Zealand
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The Empty Forest

• While many Neotropical Forests appear intact
• That is, many areas are not deforested
• Hunting has depleted many species

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The Empty Forest
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I hate fire ants, but
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Citrus Ants and Citrus

• Citrus ants, Oecophylla
• Eat bugs that infest citrus in China
• Weave nests of silk to construct nests
• Nests are placed in trees by farmers
• But ants also harvest Homopteran nectar

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Weaver ants continued
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The Food Web simplified version
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Defining a Keystone species
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Introduction of species can alter food webs