BIOGEOGRAPHY
Island Biogeography
Many Biogeographers, including Wallace and Darwin, were stimulated to understand evolution thru island life.
MacArthur and Wilson (1963, 1967) developed the influential equilibrium theory of island biogeography.
The fundamental points of the model are:
the species area curve
S=Caz Where S is the number of species, c is the intercept, A is the area of the island, and z is the slope of the regression.
log(S)=log(c) + z log(A)
Smaller and more isolated islands have fewer species per unit area and steeper slope, z, for the relationship between log S and log A because extinction rate is greater on smaller islands
and colonization rate is lower for smaller, isolated islands.
The concept of equilibrium is appropriate, because of "turnover" or dynamic interaction between extinction and colonization of islands.
The colonization rate declines and the extinction rate increases as the number of species in the fauna increases. Representing these rates as concave-up curves allows us to represent S [S hat] as the equilibrium between opposing rates of colonization and extinction.
Notice the effect on species number S [hat] and turnover, T [hat]
of colonization distance on immigration rate
and the effect of island size on extinction rate.
Questions regarding the model:
How will speciation affect S?
How will evolution of niche partitioning affect coexistence and S?
How might the shape of the I and E curves differ?
Are all species equal?
Island area can affect immigration in addition to extinction.
How might island isolation affect extinction?
How does habitat diversity relate to island size?
What are examples of nontypical islands?
How do habitat island differ from more isolated islands?
How do diverse community processes affect alternate equilibria?
How do different dispersal adaptations affect the model?
Where in the model will speciation occur? (Fig. 13.29)
How will succession affect the colonization rate? (Fig. 13.27