Island Biogeography Flashcards
What kinds of Islands are there?
Water-surrounded islands
- oceanic
- continental
- lake islands
Land-surrounded islands
- virtual islands
- fragmented land
Why are islands so special?
- Excellent biogeographical processes
- evolution is evident due to isolation
- home to the weird and wonderful!
What are virtual islands? Where are the important?
- agriculture
- fragmented forest
- important to climate change, conservation and agriculture
What important concepts are there?
- stepping stones
- corridors
- species area relationships
What sinter difference between oceanic and continental islands?
Oceanic
- are not, and never have been connected I a mainland landmass
Continental
- are not, but have been connected to mainland landmass
- only separate due to sea-level rise
What input lids Wallace have with the identification of oceanic and continental islands?
- He initially noticed a difference.
- couldn’t originally explain the variance between Bali and Lombok islands.
- invented Wallace’s line between the two islands
What did Wallace discover with Bali and Lombok island?
Bali and Lombok separated by small amount of very deep water
Bali
- was similar to java and Sumatra in physical structure and animal/flora species
- mammals present
- less diverse bird species
- continental island
Lombok
- not similar to java and Sumatra
- occupied by many different bird species
- no mammals
- oceanic island
What did Wallace find with Aru and Ke islands?
Similar to Bali and Lombok
Aru was similar to nearby mainland
Aru as a continental islands
Ke was not similar to nearby mainland
Ke was an oceanic island
What process and speed do species arrive on islands?
Oceanic islands
- evolution is faster that immigration
Continental islands
- immigration is faster than evolution
What Island species process types are there?
Local extinction
Immigration
Speciation
Island equalibrium
- some colonisation will result in extinction due to predation or competition
- species number will increase due to immigration and speciation.
- eventually the rate of increase will balance the rate of decrease
New islands have no species at all
What are the colonisation rates on oceanic islands?
Two important factors:
Isolation
- the further away from a mainland landmass an island is the liner it take to populate the island
Size
- a large island has more coastal landing space
- also larger inland area to fill
- despite size take longer to populate than a small island
What special species traits are there with island species?
Giantism
- Galapagos tortoises
Dwarfism
- minute chameleons in Madagascar
Flightlessness
- kiwi in New Zealand
Explain diversity of island species
Fewer species per unit area than on islands than mainland
Jarak island
- 34 species of tree in every 0.4ha plot
Malayan mainland
- 98 species of tree per 0.4ha plot
What’s unusual about polarity of islands?
- islands have more polar features and flora than ty are similar to near by mainlands
Eg
- Galápagos Islands loaded on equator and should be tropical. In reality: it is arid
- Canary Islands are located next to Africa but is Mediterranean
Are species in islands sub-sets of nearby mainland species?
NO
it is not the reputable nearness of the species which matters, it’s the dispersal power of the species
How are island facilitators of dispersal?
Stepping stones
Occupied mainland –> island 1 –> island 2 –> unoccupied mainland
Why are island species area curves?
- though that larger islands have more species thank smaller islands
- there is not a linear increase of species and size of islands
2 confusing hypothesises
- The number of species in and area increase with the size of the habitat
- Increase in species within increasing size of area occurs at a decreasing rate
Talk about the Rakata Theory.
- Krakatoa eruption left and island 1883
- Study of island development started from 1886 to present day
- colonisation not as simple as the theory suggested
- climatic and geographical changes influenced the colonisation and extinction rate
What was the process of colonisation in the Rakata case study?
E = eruption
Studied the colonisation of flora on coastal region
E+3 - 9 species
E+14 - 23 species
E+25 - 46 species
Inland plant succession
E+3 - 50% of vegetation were ferns
E+14 - grassland
E+100 - forest cover grassland
Could the Rakata theory easily predict the abiotic or biotic factors?
Abiotic factors where easy to predict as they involved aspects such as
- island area
- position
- isolation
Biotic factors were not so easily predicted. For factors such as - predation - competition and - disturbance There are not rules
