Darwin's Finches

Hot off the presses is a new paper about Darwin's Finches published in the journal Science this week and reported on in the San Francisco Chronicle yesterday.

Darwin's Finches are a group of 14 closely related birds found on the Galapagos Islands whose beaks have adapted to the foods found on the specific islands they live on. Darwin did not initially realize that these birds were closely related and only later did the work of others convince him that this was so. Darwin then speculated that all these birds must have once had a common ancestor.

For the last 33 years Peter and Rosemary Grant have been studying Darwin's Finches on the Galapagos Islands. In the current paper they describe how the new colonization of one island by a species of finch (Geospiza magnirostris) led to a rapid evolution of a finch that was already present on the island (Geospiza fortis).

The newly arrived species of finch was able to break open and eat large seeds three times faster than G. fortis could. Over the years 2003 and 2004 little rain fell and competition for food was fierce. The only G. fortis to survive had short beaks and fed on smaller seeds where they did not compete with the larger billed G. magnirostris.

This is an example of both directional selection and character displacement. Although this is almost certainly common in nature it is rare that scientists are on hand to document it, and it may be rare that it happens this quickly.