Aresearcher is comparing the species diversity of two islands. both islands are roughly equal in size. however, one island is much closer to the mainland. she determines that the s value for the island closer to the mainland is the s value for the island located farther from the mainland. in addition, she finds that the closer island's extinction rate is the extinction rate on the farther island.

Explanation:

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.