An international team of researchers used the largest genome data set of nearly 4,000 Darwin's finches to study evolutionary changes in this iconic bird. The study, published in the journal Science, builds on decades of research to reveal the genetic basis of finch adaptations and highlights the importance of long-term observations in understanding evolutionary mechanisms.
An international team of researchers recently published a landmark study of contemporary evolutionary changes in natural populations. This study draws on the most extensive genome dataset of nearly 4,000 animals in their natural habitats in Darwin's finches to reveal the genetic basis of adaptations in this iconic group. The findings were recently published in the journal Science.
Ever since Darwin wrote about the finches of the Galapagos Islands, biologists have been studying these small songbirds to understand how they evolved. Over the past million years, one ancestral species evolved into 18 different species. The advantage of Darwin's finches as a study organism is their ability to demonstrate early stages of species evolution.
Peter Grant and Rosemary Grant of Princeton University have been tracking nearly every individual of Darwin's finches since the 1970s. Their research shows that Daphne-Major's finches evolved in response to environmental changes and interactions between species. An international team of researchers has sequenced the genomes of nearly all the finches studied on Daphne Island and revealed the genetic structure of adaptive changes.
"I think this is a very exciting opportunity to combine our understanding of evolutionary changes deep in the past with current observations," said Erik Enbody, first author of the study and a former postdoc at Uppsala University. "Genomic data are a powerful tool that allow us to look at birds in the field and understand the factors that influence their evolution, and a study of this scale would not be possible without decades of research on the Galapagos Islands."
Leif Andersson (Uppsala University and Texas A&M University), senior author of the study, said: "One of the striking features of our discovery is that only a few genetic loci can explain the large amount of variation in finch beaks. One of the ways these genetic changes appear to evolve is by bundling multiple genes together and then allowing natural selection as the environment changes."
These results may surprise human geneticists because many genetic variants account for only a small proportion of the variation in height among humans.
Over the three decades studied, the beaks of the finches got smaller. Using the genomes of all the finches on Daphne, the researchers found that this was because genes from the lesser ground finches were transferred through interbreeding and periods of drought, in which individuals with smaller beaks survived better. This study highlights the value of long-term studies for understanding mechanisms of evolutionary change.
The researchers collected a drop of blood from each bird's wing vein and attached a band to each bird. This allows them to be tracked to determine how long they survive, who they mate with, and their offspring.
Rosemary-Grant added: "By collecting blood samples throughout the study, we can use the samples for genomic studies when the technology is mature."
The researchers studied not only the midland finches, but entire communities of the island's four finch species. As conditions on the island changed and hybridization with medium-sized finches increased, the common cactus finch's bill gradually became blunted. This study paints a dynamic picture of how species adapt to changing environments through genetic changes and sometimes large phenotypic effects that are passed between species. As the global environment continues to change, the finches on the Galapagos Islands will provide a valuable window into how birds, their genetic makeup and their environment interact to shape the future of wild populations.