4.3 - Theory of Island Biogeography

Question 1

What is island biogeography?

Answer 1

• Study of ecological relationships & community structure on islands
• Islands can be actual islands in a body of water or figurative habitat islands such as central park in New York City or National Parks (nat. habitats surrounded by human developed land)

Question 2

What are the two basic rules or observations of island geography?

Answer 2

1. Larger islands support more species
2. Islands closer to the mainland support more species

Question 3

How do larger islands support more species?

Answer 3

• The larger the island, the greater the ecosystem diversity
• Greater ecosystem diversity = more food & hab. resources
• More niches, or “roles” organisms can play in the ecosystem

Question 4

How does an islands location effect species population?

Answer 4

• Easier for colonizing organisms to get to island from mainland
• More colonizing organisms = more genetic diversity in new pop.

Question 5

What does Larger Islands equal?

Answer 5

Larger islands =
- higher ecosystem diversity
- More available “niches” or roles
- Ex: all the different food sources available to birds
on Galapagos
- Larger pop. sizes (more genetically diverse and more resistant to env. disturbance)
- Lower extinction rate (species less likely to die off)

Question 6

How does larger islands relate to species richness?

Answer 6

There is a positive correlation between island size & species richness

Question 7

What does islands closer to the mainland equal?

Answer 7

• Easier for more species to migrate to island from mainland (swim/fly)
• More continual migration of individuals to the island habitat
• Frequent migration brings more genetic diversity & larger pop. size
• Inverse relationship between island distance from mainland & species richness
  - The further away from mainland, the fewer species
  (higher pop lower distance… technically inverse)

Question 8

How does island distance relate to species richness?

Answer 8

Closer to mainland = higher species richness

Question 9

What is adaptive radiation?

Answer 9

single species rapidly evolving into several new species to use diff. resources & reduce competition

Question 10

Explain Evolution on Islands

Answer 10

• Islands have limited space & resources, creating unique conditions for evolution
  - More pressure for species to adapt to narrower niches (more specific food/hab.)
• Adaptive radiation = single species rapidly evolving into several new species to use diff. resources & reduce competition
• Different beaks quickly evolve to fit variety of different food sources on Island
• Single colonizing species from mainland quickly evolves to many slightly different species to adapt to new island cond.