Geog 316: Biogeography
SFSU Fall 2006
Dr. B.A. Holzman
Dr. Barbara Holzman
Island Biogeography
Islands
Continental/Oceanic
Problems/ Issues
Access/Isolation
Habitat
Hazards
Theory of Island Biogeography
MacArthur and Wilson
Problems w/ theory
Natural Reserve Planning
Continental vs. Oceanic
Islands
Continental islands
Continental islands are bodies of land that are connected by the
continental shelf to a continent. That is, these islands are part
of an adjacent continent and are located on the continental
shelf of that continent. Ex. Greenland, Barbados, Trinidad,
Sicily, Sumatra, New Guinea, Tasmania.
For the exclusive use of students enrolled in Geog 316.01 Fall 2006
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Geog 316: Biogeography
SFSU Fall 2006
Dr. B.A. Holzman
Oceanic Islands
• islands that are not
part of continental
shelf areas, they are
not, and have never
been, connected to a
continental land
mass, most typically
these are volcanic
islands.
Volcanic islands
Volcanic islands are built by volcanoes, not geologically part of any
continent. One type of volcanic island is found in a volcanic
island arc. These islands arise from volcanoes where the
subduction of one plate under another is occurring. Ex. Mariana
Islands, Aleutian Islands, Tonga, etc.
Another type of volcanic island occurs where an oceanic rift
reaches the surface. Ex. Iceland.
The last type of volcanic island are
those formed over volcanic hotspots.
A hot spot is more or less stationary
relative to the moving tectonic plate
above it, so a chain of islands results
as the plate drifts. Ex. Hawaiian
Islands,
Concepts/Issues
1) Nature of the island biota
How does it differ from the source area(s)?
What is the nature of the immigrants that
allowed them to reach and colonize the
island?
For the exclusive use of students enrolled in Geog 316.01 Fall 2006
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Geog 316: Biogeography
SFSU Fall 2006
Dr. B.A. Holzman
2) Identify and quantify the factors that
control:
- Rate at which new species reach an island
- Rate at which species become extinct on an
island
- Number of species an island can support
3) Process of evolutionary change by which
an island becomes an integrated ecosystem
- Each organism adapted to physical and
biological aspects of its life on the island
- Occupation of niches
Islands and Colonization
Factors:
Dispersal abilities of immigrants
Galapagos Islands: 60% by bird, 30% by wind, 9% drifted by sea
• Diversity of habitats:
less than 9 hectares = BEACH/ latitude, elevation, etc.
• Isolation
-- How far from source? How rich is source?
• Hazards
– Hurricanes, volcanoes, humans
• Ability to adapt
gene pool
founder effect – small population w/ little genetic variability
For the exclusive use of students enrolled in Geog 316.01 Fall 2006
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Geog 316: Biogeography
SFSU Fall 2006
Dr. B.A. Holzman
Number of Species and Area (reptiles/amphibians)
Island Area and Diversity (flora)
Island Area and Diversity
For the exclusive use of students enrolled in Geog 316.01 Fall 2006
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Geog 316: Biogeography
SFSU Fall 2006
Dr. B.A. Holzman
Founder Effect
Founder effect and
bottlenecks
Tiburon Island,
Mexico
Elephant seals
Q. Victoria Hemophilia
Amish (extra digit)
For the exclusive use of students enrolled in Geog 316.01 Fall 2006
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Geog 316: Biogeography
SFSU Fall 2006
Dr. B.A. Holzman
Evolution Unchecked
Gigantism:
Giant tortoise, Elephant bird, Komodo dragon,
Dwarfism:
Mouse lemur, pygmy mammoth, Madagascar kingfisher
Channel Islands Fox
• weighs approximately
1.8 kilograms
• smallest fox species in
the United States
• predators: golden eagles,
humans
Urocyon littoralis
Loss of flight
For the exclusive use of students enrolled in Geog 316.01 Fall 2006
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Geog 316: Biogeography
SFSU Fall 2006
Dr. B.A. Holzman
Relics
Published in 1967
Theory of Island Biogeography
Number of species on an island depends on
a number of factors:
• area (topography assumed)
• diversity of habitat
• accessibility to colonists
• richness of source
I.B. add…
• equilibrium between rate of colonization
by new species and extinction of existing species
For the exclusive use of students enrolled in Geog 316.01 Fall 2006
7
Geog 316: Biogeography
SFSU Fall 2006
For the exclusive use of students enrolled in Geog 316.01 Fall 2006
Dr. B.A. Holzman
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Geog 316: Biogeography
SFSU Fall 2006
Dr. B.A. Holzman
Equilibrium predicted
S=CAZ
S = number of species
A= area
C=
Modes of dispersal
Rates of immigration
and extinction
History of Rakata higher plant
flora since 1883
For the exclusive use of students enrolled in Geog 316.01 Fall 2006
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Geog 316: Biogeography
SFSU Fall 2006
Dr. B.A. Holzman
Effect of Distance From
the Mainland:
• Near Islands have a
higher rate of colonization
• Near Islands have a
higher equilibrium number
of species
Effect of Island Size:
Large Islands have a
higher equilibrium
number of species
For the exclusive use of students enrolled in Geog 316.01 Fall 2006
10
Geog 316: Biogeography
SFSU Fall 2006
Dr. B.A. Holzman
Problems with the IB Theory
• Its applicability to all organisms is in
question
• Simply looking at physical characteristics
is limited (i.e. area/isolation)
• Equilibrium can only be maintained in a
constant environment (not with climatic
disturbances/ envir. changes/ humans)
• Quantitative attempt simplifies process
Where Can We Find "Islands"?
•Oceanic Islands –
Arise from volcanic activity; Galapagos and Hawaii
•Continental Islands –
Islands that were once contiguous with the
mainland; Aleutians/Channel Islands
•Agricultural Fields
•Caves
•Fragmented Forests Mountaintops
•Hosts (Parasites see hosts as islands)
•Ponds/ Streams
•Cities (fragmented landscapes)
Application of Island Biogeography
The Theory of Island Biogeography has been used in the creation of
nature reserves, designing habitat and determining the number of species
a habitat can viably carry. Although there are many shortcomings of the
quantitative nature of the theory, some of this work has been helpful.
Nature Reserves
•Design of nature reserves can lead to problems
•How big is big enough?
•SLOSS
For the exclusive use of students enrolled in Geog 316.01 Fall 2006
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Geog 316: Biogeography
SFSU Fall 2006
Dr. B.A. Holzman
SLOSS: Single large or
several small???
• Single large
• Several small
• Connectivity
Application of Island Biogeography
To "Habitat Islands"
Habitat diversity confounds affects of area
"Edge Effect" on habitat islands
Degree of Isolation in habitat islands may be difficult
to assess
Corridors
Roadless Areas
between
Yellowstone and
Grizzly Park
For the exclusive use of students enrolled in Geog 316.01 Fall 2006
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Geog 316: Biogeography
SFSU Fall 2006
Dr. B.A. Holzman
Why Do We Care About Island
Biogeography?
"Insularity is a universal feature of Biogeography."
- (MacArthur and Wilson. 1967 )
•Applicability of Island Biogeography Models to other
"Islands"
•Island Biogeography and evolution can lead to
endemic species
• Conservation Biology
• Fragmented Landscape
• High number of Island Endemics
34% of US listed species are from Hawaiian Islands or Puerto Rico
Island Biogeography
Islands
Continental/Oceanic
Problems/ Issues
Access/Isolation
Habitat
Hazards
Theory of Island Biogeography
MacArthur and Wilson
Problems w/ theory
Natural Reserve Planning
Assignment
For the exclusive use of students enrolled in Geog 316.01 Fall 2006
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