Island Biogeography

What is island biogeography and what organisms does it refer to?

how species colonize, survive, and go extinct on islands. refers ONLY to species that originate on the mainland

How does size of an island affect the number of species on an island? (area effect)

• larger size = more species

• smaller size = fewer species

How does the distance of an island from the mainland affect the number of species on an island? (distance effect)

• more distance = fewer species 

• shorter distance = more species

What are rates of colonization and extinction on an island related to?

number of species present, distance from mainland, and island area/size

Where is the equilibrium point for rate of colonization and extinction on an island?

intersect between lines

Explain why having more species on an island decreases colonization rates, and why having fewer species increases colonization rates.

• more species = more interspecific competition for resources, fewer niches left

• fewer species = more niches to fill, less interspecific competition for resources

In terms of colonization and extinction rates, what will happen on a smaller island at the same distance the mainland as a larger island, and why?

smaller island will have higher extinction rate because smaller islands can support fewer populations, increasing extinction rates. niches are filled more quickly and there are fewer resources.

In terms of colonization and extinction rates, what does the extinction and colonization rate for a small island look like compared to a normal-sized island the same distance from the mainland??

• extinction rate is sharper, and fewer species are supported

• colonization rate is the same

In terms of colonization and extinction rates, what does the extinction and colonization rate for a small island look like compared to a normal sized island?

• colonization rate is the same

• extinction rate is higher

In terms of colonization and extinction rates, what will happen on an island of the same size but further from the mainland and why?

• lower colonization rate, harder to reach

• same extinction rate

Describe the Florida Keys experiment

• counted the number of spider species on each island in the florida keys

• theorized that, if size/distance theory is true, the same number of species should colonize each island after extermination all spider species

• found that closer islands were colonized more quickly than distant islands

• number of species returned to same number of species as before

• species composition changed