Reproductive isolation occurs between populations of organisms if two or more populations cannot interbreed and/or produce viable offspring. This results in the formation of new species.

To illustrate, if two populations of a species are isolated from each other, each population would evolve separately. This may result in reproductive isolation, which may lead to speciation.

The type of reproductive isolation may have been important in Galápagos finch speciation would be geographic isolation and behavioral isolation. Geographic isolation may have been a factor because the finches on the islands could have been classified as isolated from one another as the islands are surrounded by bodies of water too large for finches to fly to the other islands. Behavioral isolation may have been a factor because the evolved finches would most likely have different beak sizes and since finches like to mate with other finches of the same size the two groups of once were the same species have now evolved into two distinct species.

One of the recent research findings that supported Darwin’s theory of evolution was the Grants’ research. Its findings demonstrated the effects of directional selection in natural populations.

For instance, the data presented in the the Grants’ research showed the effects of competition and climate change on natural selection. It supports the theory of evolution by natural selection.

However, there are still limitations in the information presented in the Grants’ research. Even though the Grants observed changes in the phenotype of organisms, they did not observe the formation of a new species. However, they still support the notion of natural selection.