Vicariance Dispersal

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Author:
kamrunsreno
ID:
12316
Filename:
Vicariance Dispersal
Updated:
2010-03-29 00:48:40
Tags:
sweepstakes islands gigantism evolution natural resources environment
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Description:
Natural Resources Midterm
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  1. Vicariance Model
    • a once continuous area split into two
    • a barrier limits movement between areas
    • (like the breakup of Pangaea)

    
  2. Dispersal Model
    • movement of individuals away from an existing population, generally over long distances
    • dispersal ability depends on the methods & pathways available
  3. Active Dispersal (vagility)
    organism moves from one place to another under its own power
  4. Passive Dispersal (pagility)
    organism carried by some other physical agent
  5. Corridor
    • movement along continuous favorable habitat
    • “easy” for many species
    • (like the Berring Land Bridge)
  6. Filter (net)
    • selectively blocks movement of some organisms
    • organisms must be able to tolerate unfavorable habitat
  7. Sweepstakes
    • a rare, chance dispersal from one place to another across a major barrier
    • must survive journey to “new place”
    • must be able to survive in “new place
  8. Generalities of Islands:
    • dispersal =
    • usually sweepstakes
    • more plants than animals
    • fewer species in higher trophic levels
    • lots of endemism
  9. Hawaii
    • 90% of species are endemic
    • pre-human
    • habitation
    • no reptiles
    • no amphibians
    • only 1 mammal
    • mostly birds & flying insects
    • long-distance dispersal abilities
    • 400 endemic fruit flies
  10. Dwarfism
    • islands have limited space & resources
    • more smaller animals can be supported
  11. Gigantism
    • more resources
    • less competition & predation
  12. General Evolutionary Trends:
    • loss of dispersal ability
    • long distance dispersal a liability

    • loss of defensive mechanisms
    • lack of predators

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