By Meghan Bialt-DeCelie ‘19

Darwin’s finches from the Galapagos Islands are one of the hallmarks of the scientific field of evolution studies. Species classification between two organisms is determined by the ability to successfully reproduce a nonsterile progeny. Several factors such as physical, behavioral, and biological differences can cause reproductive isolation, or prevention of two organisms from reproducing. Reproductive isolation can cause speciation, or the development of a new species.

Through studying a foreign finch and its offspring in the Galapagos Islands, researchers led by Dr. Sangeet Lamichhaney from Harvard University found that reproductive isolation can occur faster than previously understood. In 1981, a single male finch came to the Galapagos Islands. It looked similar to a native species of finch, Geospiza fortis, except it was larger and sang differently. Researchers looked at the genome of the original foreign finch and found that it was the species G. conirostris originating from Española, which is 100 kilometers away.

The foreign species, as well as its offspring, was able to reproduce with the native G. fortis. The third generation, however, behaved like an independent species and reproduced among themselves; future generations never reproduced outside this lineage. This was referred to as the Big Bird Lineage. This new species succeeded because of the morphology of their beaks which gave them an advantage in acquiring food. The morphology of the beak as well as their distinctive song was likely how this lineage was reproductively isolated from the other Galapagos finches.

A foreign species of finch entered the Galapagos Islands and eventually led to the rise of a new species of finch, whose population is in the dozens. This sudden event gives researchers a different view on the mechanism of speciation. It shows that given very rare and perfect circumstances of selection and conditioning, a speciation event can occur in as little as three generations.

References:

1. S. Lamichhaney, et al,. Rapid hybrid speciation in Darwin’s finches. Science (2017). doi: 10.1126/science.aao4593.
2. Image retrieved from: https://commons.wikimedia.org/wiki/File:Galapagos_Islands_topographic_map-en.svg