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ISLAND
BIOGEOGRAPHY
What is Island Biogeography?
• A field within biogeography
 the study of the distribution of species spatially and temporally
• Establishment and explanations of the
factors which affect species richness of
natural communities
History
• Founded by Robert MacArthur and
E.O Wilson (ecologists) in the
1960s
“The Theory of Island Biogeography”
• Intention of predicting the number
of species that would exist on a
newly created island
• Began on islands
 extends over to other biomes
“Because islands are small geographic
units with distinct boundaries, they
serve as useful models to illustrate the
mechanisms of biogeographic
phenomena. Intensive ecological
studies on islands have provided key
insights into invasion and colonization
patterns, dispersal mechanisms, and
extinction rates.”
- Encyclopedia Britannica
Isolated populations can become genetically and
morphologically distinct from the original ('source‘)
population on the mainland over a period of time,
whether through natural occurrences or in relation to the
new environment.
Principle of Island Biogeography
“No island will contain the species of the mainland which
served as the sources for colonization (MacAuthur 1972).”
Immigration of species
Biodiversity of an island
is always build on the
species from its
Mainland.
-
-
Terrestrial
species(difficult)
Aquatic species (easy)
Hence, the Mainland contains bigger Biomass
Two significant factors that contribute to the rate of
species change are:
1) the area of the island
2) It’s distance from the mainland source.
Formation of ‘new species’
New species migrate from other areas (usually
mainland) and sometimes result in the extinction of
the existing species
• Competition
• Genetic inbreeding
Reaching Equilibrium
The species on the island reaches dynamic
equilibrium in population size and species
diversity
 through the process of migration and extinction.
• Once equilibrium is achieved:
– the biomass of the island stays the same
– the composition of species will change
• Evolution is a
significant
process only on
islands that are
large and stable
• On an unstable
island, species
cannot survive
longer to
undergo natural
adaptation
How can we use these principles
when designing conservation areas?