LE 14: Island Biogeography

Question 1

What are islands great systems for?

Answer 1

Biodiversity because of:
- different ages and sizes
- frequent disturbances

Question 2

What is the relationship between species and an area?

Answer 2

positive linear relationship
- as area increases, the number of species increases

Question 3

How does fragmentation, affect the diversity in an area?

Answer 3

fragmented forests = less diversity for each smaller fragment
- top predators need large fragments; decrease in fragment size = absence of predators
- competition increases leading to lower diversity

example: dams and flooding
- decline in population of trees in a smaller area
herbivores eat more trees than what can be recruited

Question 4

What is the relationship between species and distance?

Answer 4

negative linear relationship
- as distance increases, species decreases

Question 5

What is the MacArthur-Wilson Model?

Answer 5

a model that allows for predictions of how many species with be on an island, based on colonization and extinction rates

colonization rates:
- larger islands = more niches
- more colonization when there is less niches (smaller islands)
- negative exponential relationship between colonization + # of species on island
- colonization rate decreases as distance of islands increases (if same size)

extinction rates:
- species cannot go extinct if there are no species
- increase of species on an island = increase in extinction rate because of limited resources

Question 6

Graphically and algebraically, how do you find the estimation of the number of species on an island?

Answer 6

Graphically: overlay extinction and colonization rates; intersection = estimate

Algebraically: set equations of extinction and colonization rates equal to each other; x = estimate

Question 7

What are the effects of fragmentation on Wildlife?

Answer 7

They can split up space that certain organisms need, like top predators that need larger fragments.
example: highways fragment mountain lion populations
- low gene flow, genetic diversity and population
- inbreeding = less fertilization = higher extinction rate (physical deformities, sperm damage, reduced sex organs, etc)

Question 8

How do raptors indicate ecosystem health and how does fragmentation affect them?

Answer 8

Decent population of raptors (carnivores with grasping feet for hunting) = healthy
- help regulate population size of rodents and small mammals that cause disease
- natural solution to zoonotic diseases carried by rodents

Question 9

Is fragmentation always predictable?

Answer 9

no

tick example:
- larger fragments = less nymphs/ticks that are mitigated by grasslands that act as a sink for mice to not run across fragments
- smaller fragments = higher tick abundance