Summary
Predicts species richness on islands from island size and distance to the mainland.
In depth
MacArthur and Wilson (1967) predicted equilibrium species number balances immigration and extinction. Large near islands have more species than small distant ones. It informs reserve design and habitat fragments behave as islands.
The theory predicts a dynamic equilibrium with continuous turnover of species. Rescue effect is higher immigration reducing extinction. Applies to habitat patches, mountain tops and lakes.
Remember: it was one of the first quantitative theories in ecology.
The species-area relationship S equals cA to the z, with z usually between 0.2 and 0.35 for islands. Rule of thumb: a tenfold reduction in habitat area roughly halves the number of species. The theory was tested in Florida Keys mangrove islands by Simberloff and Wilson, who fumigated islets and watched recolonisation, which supported the equilibrium idea.
The theory applies to habitat islands such as mountaintops, lakes, and reserves surrounded by farmland; debates on SLOSS (single large or several small) arose from it. Reserve design has since used corridors and connectivity as key concepts. Islands also have high endemism and are vulnerable to introduced predators.
Example: Krakatoa and other volcanic islands provide cases of colonisation and extinction at the species level.
Frequently asked questions
What is Island Biogeography?
Predicts species richness on islands from island size and distance to the mainland.
Which area of biology covers Island Biogeography, and how advanced is it?
Island Biogeography is one of the 54 topics in Ecology. It is rated Advanced, so it suits learners who want specialist depth. Related topics in this area include Metapopulations, Landscape Ecology, Climate Change Ecology.
Can you give an example of Island Biogeography?
Krakatau was recolonised after its 1883 eruption.
What should I learn before Island Biogeography?
Work through the Beginner topics in Ecology first, such as Ecology, Ecosystem, Biotic and Abiotic Factors, then return to Island Biogeography. Advanced topics assume the Intermediate vocabulary.
What topics are related to Island Biogeography?
The closest topics to Island Biogeography are Metapopulations, Landscape Ecology, Climate Change Ecology, Macroecology. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Island Biogeography?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Island Biogeography. To practise the whole of Ecology, use the Ecology quiz.
How is Island Biogeography different from Metapopulations?
Island Biogeography: Predicts species richness on islands from island size and distance to the mainland. Metapopulations: A set of spatially separated populations linked by dispersal, with local extinction and recolonisation. Read both side by side and note what each one explains.
How should I study Island Biogeography step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Metapopulations and explain the difference aloud. Finally, take the Ecology quiz and come back to this page for any question you miss.