Exam 5 Island Biogeography Flashcards
A well established community with filled niches may not allow for new species.
Resistance to Invasion
Increasing distance =
Less likely to cross, fewer species can do it.
History of potential interchange =
More likely to resist invaders
The exchange between North and South America as they came together.
The Great American Biotic Exchange
Construction of the Suez Canal connecting the Mediterranean Sea and the Red Sea. Opened in 1969. 102 miles long at sea level, no locks. Passed through hyper saline lakes.
The Lessepsian Exchange
Where a taxon first evolved
Center of Origin
Thought that most derived forms of a taxon would be at the origin.
Mathews (1900’s)
Center of origin for sea snakes in Australia/New Guinea based on:
- Most diversity
- Most primitive species
- Ancestors there
Study of the distribution of lineages
Phylogeography
Any isolated geographic area.
Island
Small land masses isolated by an expanse of water.
Typical Islands
Island that was once joined to an adjacent continent. Same biota at some point in history.
Continental Islands
Separated from mainland in initial split:
Greater Antilles/Cuba
80 mya
Separated from mainland in initial split:
New Zealand
80-90 mya
Separated from mainland in initial split:
Madagascar
100 mya
Separated from mainland in initial split:
Seychelles
65 mya
An island that arose from the ocean floor and has never been connected to a continent. Thus all biota came via long distance dispersal. Species suited for long distance dispersal.
Oceanic Islands
Islands/volcanoes that formed at/near mid ocean trenches.
Aleutians
Lesser Antilles
Lesser Sundra Islands
Islands formed at a Hotspot or fracture zone.
Hawaii Islands (Hot spot) Galápagos Islands (Fracture zone)
Other types of Islands
- isolated mountaintops
- isolated nature preserves
- lakes etc.
Wallace influenced by observational studies in…
Malay Archipelago
The number of species inhabiting an island represents equilibrium between opposing rates of colonization and extinction.
Basic Theory
The Equilibrium Theory
The number of species inhabiting an island represents a dynamic equilibrium between opposing rates of immigration and extinction.
Very near islands received repeated propagules of existing species and thus those species are not extirpated.
Rescue Effect
Used Methyl Bromide to kill all Arthropods and terrestrial animals; vegetation unharmed. Small mangrove islands in Florida, Keyes
Simberloff and Wilson (1969, 1970)
Resulted in rapid recolonization within one year. Supported equilibrium theory
Censuses Arthropod individuals and number of species on thistle plants in Southeastern Arizona.
Brown and Kodric Brown (1977)
Results: mostly supported equilibrium theory and it’s predictions.
Larger plants = increased # of individuals and species.
Longer distance from source = decreased #’s
Near plants = increased numbers
Small plants had higher turnover of individuals and species.
Near plants had lower turnover rates. (Different than expected)
Island size does affect immigration =
Target Area Effect
Below a certain island size, species richness is constant =
Small Island Effect
Organisms with longer generation times have:
Lower turnover rates
Problems with the equilibrium theory:
- Many islands biota are not in equilibrium
- Ignores characteristics of a particular species and interspecific interactions.
- Colonization and extinction are seen as independent processes.
- Larger islands are larger targets
- Immigrants may come from more than one location.
- Species richness is affected by speciation in location
- Larger areas usually have larger and more diverse habitats
“Still increasing to reach equilibrium”
North American Great Lakes: 10,000 years old, few fish species, some speciation.
Africa Great Lakes: 5 mya, many fish species, much speciation and adaptive radiation.
Plant dispersal to islands.
- bird carried is most common
- wind dispersed 2nd
Galápagos Islands plants = 378 colonizations, 60% by birds, 31% by wind, 9% by seeds.
