Island Biogeography

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Island Biogeography

Island Biogeography

  • Colonization - arrival

    • float
    • fly
    • swim
    • be carried
    • wind (seeds, spores)

Surtsey (1963)

Plant colonization - Surtsey

Krakatau (1833)

Colonization - Krakatau

Characteristics of Island Species

Maquire (Ecol. Monog. 33:161-185)

  • Placed bowls of nutrient solution at various distances and heights from a pond.

  • Some bowls increased, then decreased in one species as others moved in.

  • The number of new species/unit time decreased with time. They finally reached an equilibrium state.

  • Different bowls had different species assemblages.

MacArthur and Wilson

Enclosing the “island”

Simberloff - equilibrium

Size relationships

Small Islands - high turnover rate

  • Microtus pennsylvanicus (meadow vole)

  • Clethrionomys gapperi (red-backed vole)

  • 12 red-backed voles introduced to Rock Island

    • rapidly displaced meadow vole in small woodland
    • population never > 30
    • went extinct in 3 years

Inland Islands

Species/Area relationships

Nonequilibrium theory

  • Suggested by Lawlor

  • Non-flying mammals have not come to equilibrium on oceanic islands

Relationship to Distance

  • Extinction is not likely to be affected by remoteness

MacArthur-Wilson model predictions

Assembly rules

  • Worked out by Jared Diamond

  • Three sets of rules determining the species mix on an island

    • Incidence functions
    • Compatibility rules
    • Combination rules

Incidence Functions

  • Incidence functions place species into 3 groups:

    • Species only on species rich islands.
    • Tramps - on species rich islands and with lower probability on species poor islands.
    • Super tramps - only on species poor islands.

Compatibility rules

  • Built from mutually exclusive ranges of pairs of species.

  • Certain closely related species cannot co-exist.

Combination rules

  • Based on diffuse competition rather than direct.

  • Prevents certain groups of species from co-existing.

  • Calculates the probability of a given combination being found together on an island of a given size

  • The only stochastic part is the order of arrival of the first colonists.

Example: Cuba

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