Biogeography and Continental Drift Flashcards
What is the theory of continental drift?
Alfred Wegener (1912) - All of today’s continents were once part of a supercontinent called Pangaea. Dispersalists opposed Wegener’s theories.
What is the panbiogeography and vicariance theory?
Leon Croizat (1950s) - Explains the present day patterns of taxon distribution, which were widely spread across all land-masses before barriers such as mountains and oceans fragmented those distributions.
What is the evidence for plate tectonics?
Palaeomagnetism - Presence of magnetised particles in rocks to trace movements through time.
Newly created ocean floor contains hot iron minerals sensitive to the direction of the Earth’s magnetic field.
Records show reversals in the magnetic field.
What is sea floor spreading and subduction?
Seafloor spreading - Heat convection from deeper layers causes spreading ridges where new seafloor is formed as regions move apart.
Subduction - Denser, oceanic plate moves subducts under less denser continental plate, causes mountain build up.
What are biogeographical realms?
Regional differences in endemic animals and plants
Nearctic
Neotropical
Palearctic
Afrotropical
Indo-Malayan
Australasian
What are the regional historical determinants of local community structure?
Historical contingency
Long-term geological effects
Taxon dispersal history
Unique evolutionary events
Long-term climate effects
What are the local, ecological determinants of community structure?
Habitat effects
Disturbances
Species interactions
Short-term ecological responses
Current local climate
What is community saturation?
When a community is filled with species, that no more can be added without extinctions - all niches are filled. Depends on:
- Evolutionary time
- Upper limit to niche space
- Dispersal of species from regional pool
Where is local richness higher?
Higher in communities where species are derived from more than one region, e.g. Great American Biotic Exchange.
Are communities predictable across continents?
Rainforests share:
- High rainfall
- High temperature
- Aseasonality
- Common habitat structure
- High species diversity
- Similar functional guilds
E.g. hornbills in afro-tropical and toucans in neotropical.
What is species convergence?
Convergence evolution - Independent lineages experience the same selection pressure and evolve similar traits.
