Species, Area,

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Species, Area, the Equilibrium Theory of
Island Biogeographyas a foundation paradigm in
conservation biology
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Species, Area, the Equilibrium Theory of
Island Biogeographyas a foundation paradigm in
conservation biology

• Conservation planning design
• Fragmentation effects
• Species loss equationpredicting extinction
• Island models in gene flow, metapopulations,
  landscape ecology

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• Samples, within contiguous area
• Isolates, islands, z high

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• Samples, within contiguous area, z low
• Isolates, islands

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The Plot Thickens!Richness as a f(area, distance)
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Saturation as a f (distance)
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Species-area relations

• S cAz
• z is much less than 1
• log S log c z log A
• Variation in c places and taxa
• Variation in z area and isolation
• z .10-.15 for samples
• z .18-.35 for islands
• IF z .3, 50/10 Rule

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• Island Observations
• Islands have fewer species than samples within
  contiguous continental areas as a function of
  size
• Islands have ever fewer species as they get
  smaller (z is higher)
• Isolated islands have fewer species than less
  isolated islands of the same size

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Threat 1 Habitat Loss Fragmentation

• Area decreases (Grain decreases)
• Isolation increases (Distance increases)
• Fewer species expected
• Insularization

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Occams principle of parsimony with a warning
from Einstein

• One should not increase beyond what is necessary
  the number of entities required to explain
  anything
• William of Ockham
• Everything should be made as simple as possible
  but not simpler
• Albert Einstein

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IBT
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The Theory!

• Immigration, extinction
• Straight to concave
• Turnover
• Near, Far
• Large, Small

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Immigration Rate
High
Rate of Immigration
Low
Many
0
Number of Species
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Extinction Rate
High
Rate of Extinction
Low
Many
0
Number of Species
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Equilibrium
High
Rate of Immigration
Rate of Extinction
Equilibrium
Low
Many
0
Number of Species
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Isolation
Far from Mainland
Rate of Immigration
Rate of Extinction
Number of Species
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Area
Large Island
Rate of Immigration
Rate of Extinction
Number of Species
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Equilibrium
Small, Far Island
Rate of Immigration
Rate of Extinction
Number of Species
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Equilibrium
Small, Close Island
Rate of Immigration
Rate of Extinction
Number of Species
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Equilibrium
Large, Close Island
Rate of Immigration
Rate of Extinction
Number of Species
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Equilibrium
Large, Far Island
Rate of Immigration
Rate of Extinction
Number of Species
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IBT
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Extensions of Theory!

• Target effect
• Rescue effect
• I E
• Distance MW Rescue
• Area Target MW

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Extensions of Theory!

• Target effect
• Rescue effect
• Landscape ecology matrix, patch quality, corridor

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Simberloff Experimental Test
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Another kind of evidence

• Species relaxation
• Faunal collapse
• Insularization

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Conservation Lessons of Landbridge Islands

• The Sundra Shelf after 10,000 yrs
• Island Area Initial Present
• 1000km2 S S E
• Borneo 751 153 123 20
• Sumatra 425 139 117 16
• Java 126 113 74 35
• Bali 5 66 19 71

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Land bridge islands Barro Colorado Island,
Panama 1. Hilltop 15.7 km2 of lowland tropical
forest. 2. Isolated in 1914 when Lake Gatun was
formed by construction of the Panama Canal. 3.
Knowing area and period of isolation, can model
extinction. 4. 108 species of breeding birds
in 1938. 5. Terborgh used land bridge model to
predict 17 would be lost in 50 years really 13
12 of 108.
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So why does insularizationlead to species loss?
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The 3 Step Process of Species Loss and Extinction
Debt
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The 3 Step Process of Species Loss and Extinction
Debt
Instantaneous Fast Slow
Sampling Isolation Area
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The 3 Step Process of Species Loss and Extinction
Debt
Instantaneous Fast Faster Greater Loss
as Area Slow
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The 3 Step Process of Species Loss and Extinction
Debt
Instantaneous Fast Faster Greater Loss
as Area Slow
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The 3 Step Process of Species Loss and Extinction
Debt
Instantaneous Fast Faster Greater Loss
as Area Slow
Extinction debt Steeper z
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Pattern and process(A.S. Watt 1947)

• O Chestnut Tree, Great-rooted blossomer
• Are you the leaf, the blossom, or the bole?
• O body swayed to music, O brightening glance
• How can we tell the dancer from the dance?
• --WB Yeats

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The Species Loss Equation

• SNOW cANOWz
• SORIG cAORIGz

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The Species Loss Equation

• SNOW / SORIG (ANOW / AORIG ) z

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The Species Loss Equation

• SNOW / SORIG (ANOW / AORIG ) z
• Critique?