The theory of Island Biogeography predicts the equilibrium number of species exp

Question

The theory of Island Biogeography predicts the equilibrium number of species expected on a given island. Researchers tested this theory on native (solid circles and lines) and exotic (open circles and dashed lines) plant communities of multiple islands in Boston Harbor (all regressions were statistically significant; reported P-values are for a test of equal regression slopes):

a) In general, what did their results reveal about the hypothesized relationships between distance from the mainland and size on the equilibrium number of species on an island?

b) Do their data support or reject the theory? Does it matter whether you consider native or exotic species? Explain.

c) What ecological mechanisms might explain any observed differences between native and exotic plant species distributions?

Explanation / Answer

a)

The number of species at equilibrium point is correlated with island size and distance from mainland. The species equilibrium shown here is dynamic and the immigration, extinction continue and species composition and richness may vary and change over time.

b)

This data supports the theory and the species richness increases with island size. It also predicts that the number of species decrease with increase in remoteness of the island area.

c)

Over a period of time, the abiotic components that cause stress such as storms and adaptive evolutionary changes in species and speciation at some other areas cause differences in native and exotic species composition on distribution of plant species on islands.

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