Island Biogeography

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Island Biogeography
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Island Biogeography

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

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Surtsey (1963)
25 miles from Iceland
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Plant colonization - Surtsey
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Krakatau (1833)
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Colonization - Krakatau
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Characteristics of Island Species

• Good dispersal ability
• Flock loving animals
• Prefer fresh water, mangroves, secondary forest
  on the mainland
• High ecological flexibility

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Maquire (Ecol. Monog. 33161-185)

• 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.

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MacArthur and Wilson
High
As species ?, there are more species which could
go extinct.
E
Rate of immigration or extinction
As species ?, the probablility of arrival of new
species ?
I
of Species is a dynamic equilibrium
Low
Number of species on island
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Enclosing the island
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Simberloff - equilibrium
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Size relationships

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

E large
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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 gt 30
• went extinct in 3 years

Meadow vole
Red backed vole
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SABA
MONTSERRAT
CUBA
Hispaniola
Cuba
Puerto Rico
Jamaica
Montserrat
Saba
Redonda
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Inland Islands

• Mountain tops in New Guinea

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Species/Area relationships
For most islands z falls between .24-.34 For
areas of the mainland z is between .12-.17
Slope of regression line relating S to A
of species
S CAz
Area
Constant, gives number of species when A 1
Species/Area Curve
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Nonequilibrium theory

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

Text fig. 24.21
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Relationship to Distance

• Extinction is not likely to be affected by
  remoteness

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NEW GUINEA
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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

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Assembly rules

• Worked out by Jared Diamond
• Three sets of rules determining the species mix
  on an island
• Incidence functions
• Compatibility rules
• Combination rules

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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.

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Compatibility rules

• Built from mutually exclusive ranges of pairs of
  species.
• Certain closely related species cannot co-exist.

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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.

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Example Cuba
Banana quit
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