Rearrangement of existing genes can rapidly create new species

Even a single gene, reworked or regulated in new ways, can fuel repeated bursts of evolutionary innovation, according to a recent study of avian birds.

A study was recently published in the peer-reviewed journal, Sciencestating that evolutionary innovation (which can lead to speciation) can occur rapidly, either by genetic rearrangement of a single gene or by exposing it to new regulation. This contrasts with the conventional wisdom known as “racial gradualism,” where evolution is believed to be a slow and gradual process based on the accumulation of genetic mutations over time that eventually give rise to new physical or behavioral variations.

This recent study, in contrast, finds that new regulation or rearrangement of existing genes, either in an existing species or through hybridization between species, can create new physical or behavioral traits very quickly, even within a single generation. This model of evolution reveals that evolutionary change can occur suddenly, after long periods of little or no visible change. Known as “marked equilibrium,” this hypothesis was first proposed by Stephen Jay Gould and Niles Eldredge in 1972.PDF).

THE Spanish wheat composites reveal how biodiversity arises

In this study, a team of scientists documented rapid, repeated bursts of evolutionary innovation in sparrow-sized insectivorous songbirds known as wheatears. Oenanthe species, living in open country. Most wheats have a distinctive white or light-colored ear, a feature that inspired their curious common name, which is believed to be a linguistic corruption of “white male.”

In addition to their white males, wheatears have a variety of distinctive black and white plumage patterns on different parts of their bodies. They are closely related species that include, the Spanish species complex, which hybridizes widely, a feature that enables astute observers to make a reasonable guess as to the parentage of a particular bird based on the location of black and white plumage patches seen in hybrid offspring. This variability, seen in the neck, neck and mantle (upper median spine), differs between species, making them an ideal model for understanding how different combinations of genetic variants create phenotypic diversity that can lead to the birth of new species.

But how does this evolutionary variability arise?

Changes in even a single gene or its expression can explain many examples of rapid adaptive evolution in these birds, and yet it is unclear how often pre-existing variation leads to this kind of complexity and how the underlying genetic architecture constrains it.

In a genome-wide association study of 335 individual birds, molecular ecologist Reto Burri, whose primary affiliation is with Swiss Ornithological Instituteand a large international group of collaborators began investigating the genetics of wheat neck color. They identified five specific single nucleotide polymorphisms (SNPs) on chromosome 20. These SNPs were clustered near the gene encoding the agouti signaling protein (ASIP), which regulates the production of melanin, thus changing the color of the plumage.

Because the color differences created by ASIP are usually the result of changes in gene expression levels, the researchers looked for a genetic element that could act as a “rheostat” to regulate ASIP levels. They discovered a long-term repeat (LTR), a genetic regulatory element located next to it ASIPwhich can be increased ASIP expression, thus creating plumage that is either black or white.

Upon further investigation, the team discovered that a white-throated O. pleschankaand a black-throated warbler, O. melanoleucashared the same group of DNA variants in this genetic region, suggesting that other genetic factors must be involved.

“Neck coloration is entirely explained by the combination of coding mutations within ASIP with the presence/absence of an LTR retrotransposon found upstream of ASIP. Mantle and side of neck coloration, simultaneously, are encoded by a series of (17) single nucleotide variations upstream of ASIP,” Dr. Burri told me.

The researchers then identified additional SNP variants linked to coat and neck coloration, which appeared to have a cumulative effect: more “white” SNP variants at these loci were needed to produce a white coat.

Where did these evolutionary traits come from? A population genetic analysis showed that the white neck and mantle coloration first appeared in O. melanoleuca and then spread to all species through hybridization (introduction).

These findings indicate that multiple interaction ASIP-Associated variants collectively shape black-and-white coloration in pterosaurs, and that repeated, hybrid-driven, articulated recombinations of these variants have contributed to the convergent evolution of plumage color across species.

Dr. Burri believes that these color shifts were maintained in the population because they probably helped the white-throated birds more efficiently exploit specialized foraging niches.

What surprised you most about the findings of this study?

“I think the biggest surprise was how beautifully wheat coloration illustrates evolution in action. It shows that either-or questions rarely have a single answer, but that many types of variation and evolutionary processes play together to form the phenotypic and diverse species around us,” Dr. Burri told me over email.

The location of these black and white patches is characteristic of each species.

“What’s exciting to see is how we can see the ASIP variation by eye and say rather confidently what the bird it came from must have looked like,” Dr. Burri explained in the email.

Furthermore, these findings highlight how multiple ASIP– associated variants collectively shape the black-and-white gradations of wheat bract color, helping to create rapid evolution in wheat species.

“[I]It is impressive to see the fine scale at which this ASIP variant recombined in hybrid zones. We’re not even looking at 50,000 DNA base pairs that are very closely related,” Dr. Burri explained in the email. “Some variants that code for mantle coloration are only tens of base pairs apart, but recombination managed to mix up that variation.”

Dr Burri pointed out that such huge genetic diversity is an evolutionary advantage for species as they adapt to dramatic climate change.

“Species that have a wide range of genetic makeup are more likely to adapt to a rapidly changing environment,” Dr Burri concluded.

Source:

Dave Lutgen, Valentina Peona, Madeline A. Chase, Niloofar Alaei Kakhki, Fritjof Lammers, Stacey G. de Souza, Anne-Lyse Ducrest, Marta Burri, Pavlos Andriopoulos, Sifiso M. Lukhele, Michaella Moysi, Elizabeth Yohanrascour, Elizabeth Yohanrakolaba, Alizabeth Yohanaklas, Abdinaba Auchli, Vasilios Bonjorlos, Iulios Christoforou, José Luis Copete, Egidio Fulco, Jesus T. Garcia, Zurab Javakhishvili, Anna Kazazou, Fumin Lei, Yang Liu, Nika Paposhvili, Robert Patchett, Áron Péter, At Raphander S. Shurulinkov, Sergey Sklyarenko, Borut Stumberger, Abulfaz Tagiyev, Alessia Uboldi, Nikitas Vogiatzis, Fanny Taborsak-Lines, Joel Gruselius, Liqun Yao, Catherine L. Peichel, Alexander Suh, Pierre-Alexandre Gagnaire Schelweith, Alexander Schelwee Reto Buri. (2025). A mosaic of vertebrate variation in a single gene underpins convergent plumage coloration, Science 390(6770) | doi:10.1126/science.ado8005

© Copyright by GrrlScientist | hosted by Forbes | LinkTr.ee

Social: Bluesky | Antisocial | LinkedIn | Mastodon Science | Weak | Understack | Threads | Twitter