2. Explain the factors that led Wilson to the idea of (a) studying small islets, (b) fumigating them, and (c) observing the recolonization of species.

Answer and 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.

Experiment:

To prove that the observations about the species richness and its relation to island size and distance to the continent were not a casualty, manipulation experiments were developed. These experiments helped to prove how the colonization process take place from cero. To observe the entire process of ecological succession and the tendencies proposed by the island biogeography theory Wilson and Simberloff (1970) eliminated the fauna on some islands to observe how they were recolonized from the continent. They fumigated the mangler island and studied these islands to account for the variation in arthropod richness over time. They studied many islands classified by distance. On each island, the richness increased at different rates.  The island closest to the continent received more immigrants and is colonized faster than the other ones, reaching its original richness faster. The farthest island was recolonized but at a much lower rate and it does not reach equilibrium while the study was going on. Although, it was expected to reach equilibrium with time.  

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