New species of Galapagos finch can emerge after just six consecutive droughts, scientists say

The Galapagos is a province in Ecuador well known for the diversity of finches, who helped British naturalist Charles Darwin uncover the process of evolution by natural selection

Scientists have revealed that just six consecutive droughts can lead to the emergence of a new species of finch in the Galapagos islands.

The Galapagos, an Ecuadorian province, is renowned for its diverse finch population, collectively known as Darwin’s finches due to their role in helping British naturalist Charles Darwin understand evolution by natural selection. Researchers discovered that drought events can alter the shape of a finch's beak, making it larger and significantly changing the sound of their songs over generations. They found that older birds may struggle to recognise the calls of younger generations if their beaks evolve due to successive droughts, complicating mating within the same species.

The findings, published in the journal Science, suggest that physical changes in birds caused by extreme events "provide a pathway" for a new finch species to form. Jeffrey Podos, professor of biology at University of Massachusetts Amherst in the US and the paper’s senior author, said: "I started working with these birds 25 years ago."

"In my very first publication on the finches, back in 2001, I showed that changes in the beaks of Darwin’s finches leads to changes in the songs they sing, and I speculated that, because Darwin’s finches use songs to attract mates, then song changes related to beak evolution could perhaps catalyse ecological speciation (process by which new species arise due to adaptations to different environments)."

British evolutionary biologists Rosemary and Peter Grant announced in 2017 that they had observed the emergence of a new finch species on Daphne Major, a tiny island in the Galapagos. This speciation event transpired within just two generations, marking it as a first-of-its-kind observation by scientists directly in the field.

Darwin's finches, a group encompassing roughly 18 different passerine bird species, are noted for their remarkable variation in beak size and functionality. Researchers were eager to understand if shifts in climate or the availability of resources like food and water could spark the development of new species.

The scientific team generated digital versions of the mating calls, simulating how these would alter if the finches' beaks evolved larger after successive droughts. Prof Podos revealed: "Essentially, we engineered the calls of future finches."

They discovered that finches with bigger, thicker beaks—adapted for crushing tough seeds during droughts—tended to sing more slowly. When the simulated songs of "future finches" were played back to the current ones, the researchers found the birds did not respond to the calls.

Katie Schroeder, the paper’s co-author who participated in this research during her doctoral training under Prof Podos, said: "We found that there were no changes in the finches’ responses to our modified calls even when the simulated songs had changed by the equivalent of three drought events."

"But by six drought events, they had changed so much that the finches barely responded at all." The researchers said that because of the links between beaks and song, an entirely new species of Darwin’s finches could evolve in response to six major Galapagos droughts.