Island Biogeography
Biogeography is the geographical distribution of organisms and how and why that changes over time. It is closely linked to the study of biodiversity, or the number of different organisms in a specific area.
Island biogeography stemmed from the works and observations of Charles Darwin and Alfred Wallace, two of the forefathers of the theory of evolution.
Island biogeography stemmed from the works and observations of Charles Darwin and Alfred Wallace, two of the forefathers of the theory of evolution.
Wilson was part of an experiment to test theories on island biogeography in 1965. In this experiment, he and a colleague, mathematician Daniel Simberloff, first observed all the species living on several small mangrove islands in the Florida Keys. Then, they fumigated the islands, killing the animals off. They observed which species came back, and to which level they came back to. E. O. Wilson and Simberloff found that although species would colonize an area to the same point of biodiversity, the area would be colonized by different species.
This experiment gives us an understanding of how islands are populated, and it also tells us that after a localized extinction event, the unique species that once lived there will not come back. The experiment also provided more evidence that the larger a habitat, the more species can live there sustainably, while conversely, the smaller the habitat, the less species can live there, and do so with a much higher likelihood of extinction. This provided scientists and conservationists with proof that protection of species from human action would take more than tiny wildlife reserves.
The mangrove islands experiment helped Wilson and Robert MacArthur to prove their own theory of island biogeography, in their book The Theory of Island Biogeography. They came to the conclusion that there was an equilibrium in the number of species that could exist in a place, even with species going extinct (called turnover) and immigrating, assuming that there is little or no evolution occurring and that niches are filled randomly. This means the model applies well over shorter periods of time when evolution does not have time to occur to a significant degree.
Wilson also used the data from the experiment to determine a relationship between island size, distance from other islands or the mainland, and species equilibrium. In the experiment, islands closer to the mainland repopulated faster than those further away, and smaller islands were able to support fewer species. This lead to the findings illustrated in the graph.