Transcript Island Ecology

Island Biogeography
Island Biogeography
o
Colonization - arrival
– float
– fly
– swim
– be carried
– wind (seeds, spores)
Surtsey (1963)
25 miles from Iceland
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Plant colonization - Surtsey
Krakatau (1833)
Colonization - Krakatau
anak Krakatau
Characteristics of Island
Species
o
Good dispersal ability
o
Flock loving animals
o
Prefer fresh water, mangroves,
secondary forest on the mainland
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o
High ecological flexibility
Maquire (Ecol. Monog. 33:161-185)
o
Placed bowls of nutrient solution at various
distances and heights from a pond.
o
Some bowls increased, then decreased in
one species as others moved in.
o
The number of new species/unit time
decreased with time. They finally reached an
equilibrium state.
o
Different bowls had different species
assemblages.
As species , there are more
species which could go extinct.
E
Rate of immigration
or extinction
High
MacArthur and Wilson
I
As species , the
probablility of arrival of
new species 
# of Species is a dynamic
equilibrium
Low
Number of species on island
Enclosing the “island”
Simberloff - equilibrium
Size relationships
o
If same
distance from
mainland,
immigration
should be the
same
Rate
E small
E large
I
S
S
Number of Species
Small Islands - high turnover rate
o
Microtus pennsylvanicus (meadow vole)
o
Clethrionomys gapperi (red-backed vole)
o
12 red-backed voles introduced to Rock Island
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– rapidly displaced meadow vole in small
Meadow vole
woodland
– population never > 30
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– went extinct in 3 years
Red backed vole
Number of amphibian and reptile species
SABA
MONTSERRAT
CUBA
Hispaniola
100
Cuba
Puerto Rico
Jamaica
10
Montserrat
Saba
Redonda
1
10
100
1,000
Area (square miles)
10,000
100,000
Inland Islands
Mountain tops in New Guinea
Species/Area relationships
For most islands z falls between .24-.34
For areas of the mainland z is between .12-.17
# of species
Slope of regression line
relating S to A
S = CAz
Area
Constant, gives
number of species
when A = 1
Species/Area Curve
Nonequilibrium theory
o
o
Suggested by
Lawlor
Non-flying
mammals
have not come
to equilibrium
on oceanic
islands
Text fig. 24.21
Relationship to Distance
o
Extinction is not
likely to be
affected by
remoteness
Rate
I near
E
I far
S
S
Number of species (percentage of sample studied)
100
NEW GUINEA
50
25
12.5
6.25
0
2,000
4,000
6,000
8,000
Distance from New Guinea (kilometers)
10,000
MacArthur-Wilson model
predictions
o
o
o
o
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
o
Worked out by Jared Diamond
o
Three sets of rules determining the
species mix on an island
– Incidence functions
– Compatibility rules
– Combination rules
Incidence Functions
o
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
o
Built from mutually exclusive ranges of
pairs of species.
o
Certain closely related species cannot
co-exist.
Combination rules
o
o
o
o
Based on diffuse competition rather than
direct.
Prevents certain groups of species from coexisting.
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
Banana quit