Island Biogeography and
Meta-population theory
Class 5
Presentation 2
Suggested readings
MacAuthur, R.H. and E.O. Wilson. 1967. The
theory of Island Biogeography. Monographs
in Population Biology.
Levins, R. 1970. Some demographic and
genetic consequences of heterogeneity for
biological control. Bull. Ent. Soc. Am.
15:237-240
Outline

Two major paradigms in conservation
biology and their influence on application
on policy and application related to
conservation
Foundations of Island
Biogeography
Started with:
MacAuthur, R.H. and E.O. Wilson. 1967. The
theory of Island Biogeography. Monographs
in Population Biology.
 They proposed that suitable habitat and
species diversity vary directly
 I.e. more habitat more species

Foundations of Island
Biogeography

Relationship could be expressed:
S = cAz
S = Number of species
c = taxon specific constant
A = Area of island
z = extinction coefficient
Species Richness
Species-Area Curves & Their
Relationship
25
20
15
10
5
0
Power
function
Exponential
1 2 3 4 5 6 7 8 9 10 11 12 13 14
10 ha
100 ha
Area (Log Scale)
Equilibrium model of island biogeography
Near
colonizing
source
Small island
R
a Far
t
Immigration
e
Extinction
Large
A
B
Number of Species
Equilibrium theory of Isld
Biogeography
Predicts that number of species will be
greatest on large islands near mainland
 As more species inhabited island
colonization rate becomes lower
 Not all species have equal probability to
migrate (filtered out)
 Stepping stone islands can speed rate of
migration

Large reserve better than small
Contiguous better than
fragmented
Small reserves close together
better than isolated small reserves
Proximity to many reserves better
than to only one
Connectedness better than isolation
Less edge better than more edge
Problems with island
biogeography
•Unable to answer important question
such as: which species would be found
in new areas
•Actual extinction rates lower than
predicted
•Needed new theory to answer question
on persistence of small populations
Origin: Meta-population theory
• First described in the 1950’s
•First experimental evidence 1958
•Found that population of predator and
prey were more stable (less oscillation)
and persistence increased when habitat
was more heterogeneous
•Found that small populations
sometimes occupy small habitats
temporarily
Definition: Meta-population

Any population that
is a population of
local populations
which are established
by colonists, survive
for a while, send out
migrants and
eventually disappear
(Levins 1970)
Levins, R. 1970. Some demographic and genetic consequences of
heterogeneity for biological control. Bull. Ent. Soc. Am. 15:237-240
Meta-population theory
Habitat islands suffer periodic predictable
extinction
 Recolonized by dispersers from
neighbouring islands
 If migration is greater than extinction
population persists

Meta-population theory
Large population: rate of sub-population
extinction not important
 If extinction rate varies with time never get
equilibrium population
 Theory suggests: important to define what
is habitat and what is not

Major difference: small pop &
local extinctions
Island Biogeography
Extinctions replaced
by re-colonizations
Persistence very rare
in reality
Meta-population
Vacant habitat recolonized but
extinction high
Unoccupied habitat
important
Small habitat
important useful for
persistence
New insights from metapopulation theory
Spatial structure important for population
persistence
 Results of application have been positive so
far

Refinements of meta-population
theory
All habitat not equal
 “Source” habitat = produce surplus, support
long term population
 “Sink” habitat = population cannot replace
itself without immigration
 Key habitat important not necessarily
habitat that supports high population

Examples of key habitat
Spawning grounds for fish
 Winter habitat for deer and moose
 Moose aquatic feeding areas
 Cavity trees

Summary
Meta-population theory has refined island
biogeography theory
 Meta-population theory suggests habitat
variability important for population
persistence
 Shifted our view of ecosystems as nonequilibrium: constant change

Summary

Shifted our attempts from preserving areas
(e.g. parks) to influencing ecosystem
processes such as fire, water regimes,
hebivory, nutrient flow.
 E.g. 1) grasslands and grazing
2) forest fire