Evolution in action detected in Darwin's finches

Evolution in action detected in Darwin's finches
The medium ground finch (Geospiza fortis) diverged in beak size from the large ground finch (Geospiza magnirostris) on Daphne Major Island, Galápagos following a severe drought. Credit: © Peter R. Grant

The most characteristic feature of Darwin's finches is the diversification of beak morphology that has allowed these species to expand their utilization of food resources in the Galápagos archipelago. A team of scientists from Uppsala University and Princeton University has now identified a gene that explains variation in beak size within and among species. The gene contributed to a rapid shift in beak size of the medium ground finch following a severe drought. The study is published in Science.

Darwin's finches are a classical example of an adaptive radiation. Their common ancestor arrived on the Galápagos about two million years ago. During the time that has passed the Darwin's finches have evolved into 18 recognized species differing in , beak shape, song and feeding behaviour. Changes in the size and form of the beak have enabled different species to utilize different such us insects, seeds, nectar from cactus flowers as well as blood from seabirds, all driven by Darwinian selection. In a previous study from the same team the ALX1 gene was revealed to control beak shape (pointed or blunt) and now a gene (HMGA2) affecting beak size has been identified.

'Our data show that beak morphology is affected by many as is the case for most biological traits. However, we are convinced that we now have identified the two loci with the largest individual effects that have shaped the evolution of beak morphology among the Darwin's finches', says Sangeet Lamichhaney PhD student at Uppsala University and first author of the study.

Evolution in action detected in Darwin's finches
Close up of the large ground finch Geospiza magnirostris that competed for food with the medium ground finch Geospiza fortis, on Daphne Major Island during a severe drought. Credit: K. Thalia Grant.

Charles Darwin was the first to describe the principle of character divergence (now known as ecological character displacement), which means that species that compete for the same food resources tend to diverge from each other and thereby reduce competition. This evolutionary process has been invoked as an important mechanism in the assembly of complex ecological communities. One of the few clear examples of ecological character displacement was previously documented in Darwin's finches by Peter and Rosemary Grant at Princeton University, coauthors on this new study. The medium ground finch diverged in beak size from the large ground finch on Daphne Major Island, following a in 2004-2005.

'We previously documented that the average beak size of the medium ground finch population became smaller during this drought due to a high mortality among individuals with large beaks because they could not compete well with the large ground finch,' say Peter and Rosemary Grant, who carried out field work on the Galápagos during a 40 year period.

'Now we have demonstrated that the HMGA2 locus played a critical role in this evolutionary shift and that natural selection acting on this gene during the drought is one of the highest yet recorded in nature,' continues Peter and Rosemary Grant.

Evolution in action detected in Darwin's finches
The most characteristic feature of Darwin's finches is the diversification of beak morphology that has allowed these species to expand their utilization of food resources in Galápagos, here illustrated by the gray warbler finch (Certhidea fusca) that has a small, pointed beak and feeds on insects, the common cactus finch (Geospiza scandens) that has a large, pointed beak and feeds on medium size seeds and cactus pollen and the large ground finch (Geospiza magnirostris) that has a large, blunt beak and feeds on large seeds. Credit: © B. Rosemary Grant.

HMGA2 has previously been associated with variation in body size in dogs and horses and it is one of the genes that show the most consistent association with variation in stature in humans, a trait that is affected by hundreds of genes. HMGA2 has also a role in cancer biology since it affects the epithelial-mesenchymal transition (EMT) that is important for metastasis and cancer progression.

'The HMGA2 gene regulates the expression of other genes but the exact mechanism how it controls beak size in Darwin's finches or human stature is unknown,' says Leif Andersson, Uppsala University, Swedish University of Agricultural Sciences and Texas A&M University, who led the study.

'It is very fascinating that this gene pops up in many different species as a gene affecting growth and in humans also as a gene affecting dysregulated cell growth in cancer. It is clear that more research to better understand the function of this gene is well justified,' ends Leif Andersson.

Explore further

A gene that shaped the evolution of Darwin's finches

More information: "A beak size locus in Darwin's finches facilitated character displacement during a drought," Science, DOI: 10.1126/science.aad8786
Journal information: Science

Provided by Uppsala University
Citation: Evolution in action detected in Darwin's finches (2016, April 21) retrieved 13 October 2019 from https://phys.org/news/2016-04-evolution-action-darwin-finches.html
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Apr 22, 2016
Given another thousand years perhaps they'll evolve up as Owls or Ostriches....for now they are still Finches, short beak, long beak or no beak. Finches.

Apr 22, 2016
I am sure crazy creationists will try to comment on this thread sooner or later. I dunno, I filter all crazies out. If they do:

Everyone, even creationists own bird watchers, accept these finches as separate species due to behavior and different bodies. That is why the scientists discuss species radiation, and why it is macro-evolution. (Typically, creationists don't accept species when in trouble, and say 'micro-evolution' when scientists all agree on macro-evolution, i.e. speciation.)

But of course, creationists can't accept basic biology when it contradicts their myths so they have to peddle lies for their mythical zombie 'Jeebus'. Rotten morals, loosing the public, and making creationist bird watchers tie themselves in knots. LOL!

Apr 22, 2016
Unfortunately what scientists are observing is micro-evolution. That is, variations within a species.

Which is part of the theory of evolution. So?

This is not "evolution" as most people know, which is supposedly a random process of species changing into other organisms.

I only know one person who uses that particular (and very wrong) definition of evolution, and that is you.
If that classifies as 'most people' then you should probably get yourself checked for schizophrenia.

What you take issue with is called speciation. Something which has also been observed:

I get that someone who believes the Earth is flat and 4000 years old cannot conceive that the evolution e.g. from a small rodent to a human takes millions of years. But don't make it out as if anyone else on this planet is as limited in their understanding of science as you.

Apr 23, 2016

Darwinianism remains completely unproven.

And you remain completely ignorant on three counts. First, in science you can never prove a theory, only disprove it. Second, this microevolution has been seen in microtime - less than 200 years. Imagine what evolution can do in millions of years. Oh, wait, you do not have to imagine - just look around you. And, third, it is Darwinism. You are so ignorant that you can't even type the name properly.

Apr 23, 2016
neb, good comments. But of course it is arguable that theories aren't facts that can be established beyond reasonable doubt, they are after all covenient descriptions of a factual process while the question is if they can be sufficiently correct.

Actually "prove" is a bit of a misnomer that hails from philosophy and math. The scientific process is testing, and sure enough we can only test for erroneous descriptions (either observations, hypotheses or theories). However, there is also competition between theories, and when no competitor is left, when you have eliminated the impossible, whatever remains, however improbable, must be the truth. There can only be One.

Theories that have no competitors and are considered facts that we will live with is the Core Theory of physics (after Higgs was found) and Evolution (after DNA was found). They can be changed in details, there can be deeper theories, but they will never be replaced. QES (Quod Erat Spectatus, as was to be tested).

Apr 24, 2016
Actually, this is exactly how evolution works. You get enough microevolution and geographical isolation and eventually you get speciation. Evolution is as much a theory as Einsteins theories of general and special relativity, both of which have survived countless tests. Evolution has passed many tests as well. There are no competing theories that come remotely close to matching our observations. And if you suggest that the magic sky man is a theory, it's not. It has no testable hypotheses.

Apr 25, 2016
Please stop calling speciation evolution because its not. Dr P Ward's books indicate periods of high CO2 produce speciation. High O2 may drive new creations but we may never know.

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