Island-Biogeography Flashcards
What is island biogeography?
How species distributions are influenced and restricted by islands - an area of habitat surrounded by an inhospitable matrix.
What are the types of islands?
Oceanic islands - never connected to mainland e.g. Hawaii
Continental/land-bridges - connected to mainland during glaciations or prior to flooding e.g. Tasmania
Virtual islands - isolated habitat patches surrounded by barrier e.g. caves and mountain tops.
How do SARs operate on oceanic islands?
Diversity lower
Area-effects are stronger
Extinction higher (no rescue effect)
Immigration lower from mainland
What are the two types of allopatric speciation?
Dispersal - Species originated in one area and dispersed into others.
Vicariance - Areas were formerly contiguous and separation occurred once barriers arose.
What is the theory of island biogeography by MacArthur and Wilson (1963)?
Number of species controlled by the rate of immigration of new species and rate of extinction of previously established species.
At equilibrium, number of species remains stable, yet composition may change.
Turnover rate - rate of species lost and gained.
What are the predictions of island biogeography?
Larger islands can support larger populations
Interspecific competition drives competition up as species richness increases, leading to extinction.
More distant islands are colonised less frequently.
Rate of colonisation declines as niches are filled.
The older the island, the more likely it is colonised.
What is the target area effect?
By chance, there is greater immigration rates expected on larger islands.
What is the rescue effect?
Islands close to source will have lower extinction rates, because they are rescued by dispersal.
What are some limitations of the theory?
No mechanistic foundation to explain patterns of species richness
No species identity
Probabilities of extinction and immigration can vary among species
Islands may not be in equilibrium
Assumes no specitation
