Date: June 23, 2015
Source: University of Groningen
Summary: The evolution of birds on the Galapagos Islands, the cradle of Darwin's theory of evolution, is a two-speed process. Most bird species are still diversifying, while the famous Darwin's finches have already reached an equilibrium, in which new species can only appear when an existing one becomes extinct. This finding expands the classical theory on island evolution put forward in the 1960s. The study is published online on June 23 in Ecology Letters.
Islands are seen as natural laboratories for the study of evolution. They form isolated ecosystems with barriers to migration. Classical Island Theory predicts that a dynamic equilibrium will occur between immigration and extinction of species. Recent theory adds that as species diversity increases, ever more ecological niches become occupied, which has a negative effect on immigration (new immigrants from outside of the Galápagos cannot settle) and diversification (radiation into new species is blocked).