Darwin’s finches offer fresh insights

A bird family that helped Charles Darwin devise his famed theory has offered new insight into island biodiversity.

Darwin’s finches, which the famous naturalist collected from the Galapagos Islands, have reached a plateau in terms of how many different species of the birds can exist at any given time, according to new research.

In the first study of its kind, scientists examined DNA from birds on the islands, including finches, to understand how the number of species had changed over millions of years.

They were investigating a theory predicting that islands can support a limited number of species.

New perspective

Scientists were surprised to find that the number of bird species in the Galapagos is rising overall.

However, Darwin’s finches were found to contradict this outcome by having a fixed number of species, with new species frequently coming into existence, but only as others die out.

Researchers from the Universities of Potsdam, Edinburgh, and Groningen say their work gives a new perspective on whether island species’ diversity is limited or not.

Most of the finch species in the study - which have differently shaped beaks according to the food available locally - are found only on the Galapagos archipelago.

Darwin devised that each species’ beak had evolved to suit the food available, which was central to his theory.

Species timeline

The research involved reconstructing the timeline of bird species arriving and diverging into new species in the Galapagos.

It provides a new framework for biologists studying island habitats.

The study was published in Ecology Letters.

Darwin’s finches have long been famous as an example of how a group can rapidly adapt to fill empty niches, but now it appears that there are limits to this.