Species-area relationships were assessed for amphibian species on two sets of islands in different regions of the Indian Ocean.

Question

Species-area relationships were assessed for amphibian species on two sets of islands in different regions of the Indian Ocean. The estimated parameters were as follows: Region 1: c=1.7, z=0.15; Region 2: c=1.25, z=0.55. It is expected that 40% of the reptile habitat will be lost to development pressure over the next decade. In which region do you expect the loss of reptile species to be greatest, and by how much? Show your work and explain your answer

Answer 1

Species-area relationships provide a framework for predicting the number of species that are expected to be lost when habitat is reduced due to factors such as development pressure. The power law model is commonly used to estimate the relationship between the number of species and the size of the habitat.

To predict the loss of reptile species in the two regions, we can use the estimated parameters for amphibian species to extrapolate to reptile species. It is important to note that this is an estimation, and the actual relationship between the number of reptile species and the size of their habitat may differ.

The power law model is N = cz^A, where N is the number of species, A is the area of habitat, c is a constant, and z is the slope of the relationship.

For Region 1, the estimated parameters are c=1.7 and z=0.15. To estimate the number of reptile species in Region 1, we can use the same values of c and z, assuming that the relationship between the number of amphibian and reptile species is similar. Let's assume that the current reptile habitat in Region 1 is 100 units of area, and 40% of this habitat will be lost due to development pressure over the next decade. This means that the new habitat area will be 60 units.

Using the power law model, we can estimate the number of reptile species in the new habitat area:

N = cz^A

N = 1.7(0.15)^60

N = 4.4

Therefore, we can expect to lose approximately 4.4 reptile species due to the 40% loss of habitat in Region 1.

For Region 2, the estimated parameters are c=1.25 and z=0.55. Using the same assumptions as above, let's assume that the current reptile habitat in Region 2 is 100 units of area, and 40% of this habitat will be lost due to development pressure over the next decade. This means that the new habitat area will be 60 units.

Using the power law model, we can estimate the number of reptile species in the new habitat area:

N = cz^A

N = 1.25(0.55)^60

N = 20.5

Therefore, we can expect to lose approximately 20.5 reptile species due to the 40% loss of habitat in Region 2.

Based on these calculations, we can expect the loss of reptile species to be greatest in Region 2, where the estimated number of species lost is approximately 4.6 times greater than in Region 1. This is because the species-area relationship for Region 2 is steeper (higher z value), indicating that reptile species are more concentrated in smaller areas of habitat. Therefore, a 40% loss of habitat will have a greater impact on the number of reptile species in Region 2 compared to Region 1.