Question

1. In islands (true islands or landscape “islands”) the main determinant of SPAR is

   1. Disturbance frequency

   2. Habitat diversity

   3. Migration vs. extinction equilibrium

   4. Sample size effect

Answer 1

Answer: Option C Migration Vs Extinction Equilibrium

Explanation

Biogeographers have often observed a reduction in the number of species on more isolated islands and this suggests an additional mechanism contributes to the SPAR. The "Equilibrium theory” of biogeography can explain both the effects of area and of isolation with a single mechanism. According to the equilibrium theory, the number of species within an area is a dynamic balance between the arrival of new species and the local extinction of species already present . The theory predicts fewer species on more isolated islands, and more species on larger islands. The predictions follow by reasoning that increased isolation from sources of immigration should decrease the rate at which new species arrive, and that populations on larger islands should be less prone to extinction. These simple mechanisms appear to be quite reasonable, although it can be difficult to disentangle them entirely from effects of habitat. For example, larger islands are also likely to provide a greater diversity of habitats , and remote, isolated islands may be subjected to climates that are different from those that are close to a mainland.