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

  • If same distance from mainland, immigration should be the same



Small Islands - high turnover rate

  • Microtus pennsylvanicus (meadow vole)

  • Clethrionomys gapperi (red-backed vole)

  • 12 red-backed voles introduced to Rock Island





Inland Islands

  • Mountain tops in New Guinea



Species/Area relationships





Nonequilibrium theory



Relationship to Distance

  • Extinction is not likely to be affected by remoteness





MacArthur-Wilson model predictions

  • Number of species should remain constant over time

  • Some species should become extinct over time

  • Extinctions balanced by immigrations

  • Turnover rate of species should vary with island area and distance from a source of immigrants



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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