A gene that shaped the evolution of Darwin's finches

Evolution of the Darwin's finches and their beaks
Large ground finch (Geospiza magnirostris) on Daphne Major Island. Reproduced with the permission of Princeton University Press. Credit: B. R. Grant.

Researchers from Princeton University and Uppsala University in Sweden have identified a gene in the Galápagos finches studied by English naturalist Charles Darwin that influences beak shape and that played a role in the birds' evolution from a common ancestor more than 1 million years ago.

The study illustrates the genetic foundation of evolution, including how genes can flow from one species to another, and how different versions of a gene within a species can contribute to the formation of entirely new species, the researchers report in the journal Nature. The study was published online February 11, one day before birthday of Darwin, who studied the finches during the 1835 voyage that would lead him to publish the seminal work on evolution, "On the Origin of Species," in 1859.

"We now know more about the genetic basis for our evolutionary studies, and this is a highly satisfactory, very exciting discovery after all these years," said Peter Grant, Princeton's Class of 1877 Professor of Zoology, Emeritus, and a professor of ecology and evolutionary biology, emeritus. Along with co-author and wife B. Rosemary Grant, a senior biologist in ecology and evolutionary biology, Grant has studied the finches for 40 years on the arid, rocky islands of Daphne Major and Genovesa in the Galápagos archipelago.

The latest study reveals how evolution occurs in halting and disordered steps, with many opportunities for genes to spread in different species and create new lineages. Given the right conditions, such as isolation from the original population and an accumulation of genetic differences, these lineages can eventually evolve into entirely new species.

Working with DNA samples collected by the Grants, researchers at Uppsala identified the gene that influences beak shape by comparing the genomes of 120 birds, all members of the 15 species known as "Darwin's finches." They spotted a stretch of DNA that looked different in species with blunt beaks, such as the large ground finch (Geospiza magnirostris), versus species with pointed beaks, such as the large cactus finch (G. conirostris).

Evolution of the Darwin's finches and their beaks
A close up of the large ground finch (Geospiza magnirostris), Daphne Major Island. Reproduced with the permission of Princeton University Press. Credit: P. R. Grant.

Within that stretch of DNA, the researchers found a gene known as ALX1, which has previously been identified in humans and mice as being associated with the formation of facial features. Mutations that inactivate this gene cause severe birth defects in humans.

"This is an interesting example where mild mutations in a gene that is critical for normal development leads to phenotypic [observable] evolution," said lead researcher Leif Andersson, a professor of functional genomics at Uppsala University, the Swedish University of Agricultural Sciences, and Texas A&M University.

But the most exciting and interesting finding of the study, Andersson said, was that the gene also varied among individuals from the same species. For example, the medium ground finch (G. fortis) species includes some birds with blunt beaks and others with pointed ones.

This finding is significant because it shows how evolution can happen, Peter Grant said. Within a species, when some individuals have a trait that aids their survival—such as a blunt beak that allows them to crack open tough seed coverings—they will pass on the genes for that trait to their offspring, whereas individuals with pointed beaks will have died. "This is the genetic variation upon which natural selection can work," he said.

The shape and size of the beak are crucial for finch survival on the islands, which periodically experience extreme droughts, El Niño-driven rains and volcanic activity. The birds use their beaks as tools to crack open the hard and woody outer coverings of seeds, pry insects from twigs, and sip nectar from cactus flowers. In times of drought, a bird that can extract food from multiple sources will survive whereas other birds will not.

Evolution of the Darwin's finches and their beaks
A close up of the large ground finch (Geospiza magnirostris), Daphne Major Island. Credit: K. T. Grant.

During the past four decades, the Grants and their research team have found that beak shape and size played a significant role in the evolution of finch species via natural selection when droughts hit Daphne Major in 1977, 1985 and 2004. "Now we have a genetic underpinning of something we have seen three times during the last 40 years," Rosemary Grant said.

The Nature study also adds to what is known about how genes are transferred from one species to another when individuals from two closely related species mate. Although in many species of birds the resulting chicks would be sterile, the hybrid offspring of Galápagos finches can mate with an individual from either of the two parental species. The resulting chicks will identify with one or the other of the parent species through song and appearance, but they will carry genes from both parents.

Through this process, known as gene flow, or introgression, genetic material can move between species and contribute to the development of new species. The Grants had shown that gene flow has occurred in the finches of Daphne Major during the past 40 years, but the new study found extensive evidence for gene flow throughout the roughly 1 million years that the birds have occupied the archipelago, which has helped the researchers update their understanding of how the lineages diverged over time.

"We've been able to get a much more confident estimate," Peter Grant said, "of which species are old and which are young, and the time course over which evolution happened."

Explore further

Research on bird beaks delivers powerful insights on variation

More information: Nature, http://nature.com/articles/DOI: 10.1038/nature14181
Journal information: Nature

Citation: A gene that shaped the evolution of Darwin's finches (2015, February 11) retrieved 16 September 2019 from https://phys.org/news/2015-02-evolution-darwin-finches-beaks.html
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Feb 13, 2015
"This is the genetic variation upon which natural selection can work," he said.

See for comparison: The Surprising Origins of Evolutionary Complexity
"Others maintain that as random mutations arise, complexity emerges as a side effect, even without natural selection to help it along. Complexity, they say, is not purely the result of millions of years of fine-tuning through natural selection—the process that Richard Dawkins famously dubbed "the blind watchmaker." To some extent, it just happens."

For a reality check, see: New insights into the hormonal and behavioural correlates of polymorphism in white-throated sparrows, Zonotrichia albicollis http://www.scienc...14001869

Biodiversity in the morphs is nutrient-dependent and pheromone-controlled as it is in species from microbes to man. Physical and chemical constraints on RNA-mediated protein folding make it impossible for mutations to lead to increasing organismal complexity.

Feb 13, 2015

Instead of "see for comparison", why don't you comment directly on the article?

The study authors make a clear case for speciation without ever mentioning pheromones

Of course they are real scientist and not a wanna be hawking perfume.

Feb 14, 2015
The study authors make a clear case for speciation without ever mentioning pheromones

Ethologists never bothered to check if pheromones controlled the physiology of reproduction in birds until nearly a decade after publication of the book I co-authored and published in 1995.

Julie Hagelin gave me a preprint of her book chapter at least a year before it was published in 2007 as "Odors and chemical signaling" in Reproductive Behavior and Phylogeny of Aves. Vol. 6B.

Several others at an annual meeting of the Association for Chemoreception Sciences had been joking about the amount of ignorance displayed by those who could not grasp the fact that the molecular mechanisms must be conserved across all species. It's no longer a joke; it's a tragedy.

Feb 14, 2015
Each species has a rich gene pool and built in mechanisms in their DNA for recombination of genes and their variants from the gene pool, which provides a rich diversity within species and rapid adaptation to light possible changes of environment with the idea to maintain complex bio balance in nature and relationship between species.

That's what can be learned by scanning my blog posts about RNA-mediated events or my PheromonesResearch FB page. Where are you finding your information Ren82?


Feb 14, 2015
Instead of "see for comparison", why don't you comment directly on the article?

Thanks for asking.

There is no model of biologically based cause and effect that supports the claims in the article. I was commenting on the article when I suggested that others read one that contained biological facts.

Feb 14, 2015
Pheromones or not the Grants have demonstrated specification, something you idiotically claim doesn't happen.


Feb 14, 2015
"21 otherwise highly conserved genes were identified that each show evidence for positive selection on amino acid changes in the Darwin's finch lineage. Two of these genes (Igf2r and Pou1f1) have been implicated in beak morphology changes in Darwin's finches."

I claim the amino acid substitutions stabilize the DNA in organized genomes, which is how nutrient uptake is linked to pheromone-controlled speciation. http://www.ncbi.n...24693353

I also claim that Vietvet is a science idiot, but everyone knows that.

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