Researchers tested the theory of island biogeography using native and exotic pla

Question

Researchers tested the theory of island biogeography using native and exotic plant communities found on multiple islands in Boston Harbor (filled circles, solid lines = native species; open circles, dashed lines = exotic species). Data were linearized via transformation with a log(x) function as needed. All regressions were statistically significant; reported P-values are for a test of equal regression slopes:

A. According to the theory, islands with the greatest number of species at equilibrium should have which characteristics? Why?

B. What do the above results reveal about the relationships between island area and local plant species richness in Boston Harbor? Isolation and richness?

C. Overall, do these results support or reject the theory (or does it depend upon whether species are native or exotic)? Explain.

D. List two ecological mechanisms that might produce any observed differences between native and exotic plant species distributions, or write N/A if there are no differences to explain.

2.5 2.0 E 1.5 1.0 0.5 0.0 P 0.05 o o log(island area) Native o Exotic TO CD E. O co 1.0 P 0.05 Native 0.5 o Exotic 0.0- 9 0.5 1.0 isolation from mainland (km)

Explanation / Answer

A)

One of the immediately obvious characteristics of islands is the number of species resident there, a number much lower and therefore more countable than the diversity on a continental mainland. Such counts can reveal interesting relationships.

A great deal of conservation research has been done on islands, because they are small, replicated units of area, isolated from other habitat. They are very useful for species, community, and ecosystem studies.

Early observations of biogeography involved the examination of the geography of biodiversity around the globe. This was followed by recognition of the species-area relationship - as area increases, the number of species present (diversity) also increases.

B)

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.

C)

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.

D)

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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