According to MacArthur and Wilson's theory of island biogeography, both the land area of an island and the contribute to species diversity

According to MacArthur and Wilson's theory of island biogeography, both the land area of an island and the distance from the mainland or continent contribute to species diversity

Explanation:

The ecologists MacArthur and Wilson took the term island biogeography theory to refer to the predictions about the number of species that could be inhabiting on an island.  

Island biogeography theory establishes that the two factors that affect species richness in natural communities on an island are the distance from the mainland and the size of the island.  

At the same time, these factors affect inmigration and extinction rates. According to the theory, islands that are closer to the continent have higher possibilities of receiving immigrants than those islands that are located farther from the mainland. This is the effect of distance.  

The effect of size is reflected in the relation between island size and species diversity.  In smaller islands, the probability of extinction is higher than in bigger islands. Bigger islands can have more species than smaller ones.      

In the case of two islands of the same size and different distance to the mainland, both of them will have the same extinction rate, but the one closer to the continent will have a higher immigration rate, and so, a higher amount of species. The S value will be higher on the island closer to the continent.

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