The Galápagos Islands have long been one of the most important places in the study of evolution. When Charles Darwin visited the islands in 1835 aboard the HMS Beagle, he collected a variety of birds and returned with them to England. At first, he believed the specimens included sparrows, woodpeckers, finches — and a single tit. Scientists later determined that the birds were all closely related finches whose differently shaped beaks had evolved to suit different foods.
The finches eventually became powerful evidence for Darwin’s theory of evolution by natural selection. The theory explains how populations can gradually change as individuals with traits suited to their surroundings are more likely to survive and reproduce.
The birds also demonstrate a process known as parallel evolution. In this process, organisms independently develop similar solutions to environmental challenges, even though the underlying genetic changes may be different.
Darwin’s Islands Continue to Reveal Evolution
“More than 150 years after Darwin’s work on the Galápagos transformed our understanding of life on Earth, these islands continue to reveal new biology,” says Professor Michael D. Martin at the Norwegian University of Science and Technology’s (NTNU) University Museum.
Martin is part of a large international research team that includes scientists from the Royal Botanic Gardens, Kew; the University of California, Davis; the University of Copenhagen; the Charles Darwin Foundation, Galápagos; the University of Georgia, Athens; the University of British Columbia; and several other institutions.
The team investigated evolution in Scalesia, a group of plants commonly called the Galápagos giant daisies. Their findings were recently published in Nature Communications.
Galápagos Giant Daisies Evolved Rapidly
“Just like Darwin’s famous finches, these plants evolved rapidly after arriving on the Galápagos from mainland South America,” explains Vanessa Bieker, a researcher at the Royal Botanic Gardens, Kew, and the first author of the new publication.
Scalesia is a relatively young plant genus. Every species that exists today emerged during the past one million years. Despite that short evolutionary history, the plants have adapted to remarkably different habitats across the islands, including humid highland forests and hot, dry lowlands.
“The appearance of different species varies dramatically, from low shrubs to tall trees. Most striking are the leaves, which range from large and entire to small and deeply lobed,” says Martin.
These lobed leaves often have intricate, serrated edges. Scientists think the shape may help plants survive dry and hot conditions by limiting water loss and releasing heat more effectively. Until now, however, the genetic changes behind this adaptation remained unclear.
Different Genes Produced the Same Leaf Shape
The researchers analyzed the complete genomes of every known Scalesia species. Their results showed that deeply lobed leaves evolved independently several times in separate branches of the Scalesia family tree.
The findings also suggest that new species may currently be developing. Numerous Scalesia populations could represent separate evolutionary lineages that scientists have not yet formally recognized.
“Even more surprising was that each time this trait evolved, it did so through different genes — even though all of them belong to the same biological system controlling leaf development,” says Bieker.
“This provides a clear example of parallel evolution: nature arriving at the same solution multiple times, but through different genetic pathways. Instead of being controlled by a single ‘master gene’, evolution appears to draw on an entire network of interacting genes, tweaking different components to produce similar outcomes.”
Rather than relying on one gene to determine leaf shape, evolution appears to modify different parts of a larger genetic network. Those separate genetic changes can ultimately produce similar physical traits.
The discovery gives scientists a clearer picture of how complex features can repeatedly emerge in unrelated populations or in different branches of the same evolutionary family.
Evolution May Still Be Creating New Species
The genetic evidence indicates that the evolutionary story of Scalesia is not finished.
“Populations within the same species show large genetic differences and have been isolated from one another for long periods. This means new species may be in the process of forming. Many Scalesia populations may represent distinct evolutionary lineages that have not yet been formally described,” says Martin.
Because these isolated populations may be following separate evolutionary paths, the researchers argue that each one should be managed as an individual conservation unit. This approach could change how conservationists protect the distinctive plants and ecosystems of the Galápagos.
The study also provides an unusually detailed view of adaptive radiation, the process through which one ancestral species rapidly gives rise to many forms suited to different habitats.
“Our findings highlight the flexibility and creativity of evolution,” says Bieker.
Darwin’s famous bird collections were not his only important discoveries on the islands. He also gathered numerous plants during his visit. Seventy-eight of those specimens were later used to identify species that were entirely new to science — including four species of Scalesia.
