Friday, 10 December 2021

Evolution News - And Then There Was One

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Common Redpoll (Male)
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Common Redpoll (Female/Immature)
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Common Redpoll (Adult male)
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Common Redpoll (Adult male)
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Common Redpoll (Female/Immature)
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Hoary Redpoll (Adult male)
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Hoary Redpoll (Female/Immature)
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Hoary Redpoll (Female/Immature)
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Hoary Redpoll (Adult male)
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Hoary Redpoll (Adult male)
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Lesser Redpoll (Female/Immature)
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Lesser Redpoll
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Lesser Redpoll
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Lesser Redpoll (Female/Immature)
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Lesser Redpoll (Female/Immature)
Common arctic finches are all the same species | Ecology and Evolutionary Biology | University of Colorado Boulder

The Redpoll is a Holarctic finch which makes occasional forays south, so, while never a common bird outside its normal range, it is a favourite of birdwatchers and ornithologists. The problem was that the range of morphologies within a species, with considerable overlap, made it very difficult to distinguish between then in the field, so birdwatchers were never sure which species or subspecies they had actually seen or whether they were really different species or subspecies.

Now, work by researchers from University of Colorado, Boulder, has finally settled the question about their taxonomic status. Detailed DNA analysis has shown that they are in fact the same species, which is highly variable due to the control of a 'supergene' which produces a range of different morphologies - the usual basis for taxonomic classification prior to the technology which enables DNA to be analysed in sufficient detail.

I think, solidly now, the new paper shows that there is widespread gene flow across the (Redpoll’s) genome, except for this one region, and it just so happens this one region influences the way they look.

Redpolls have been taxonomically confusing for a long time, and we only get to see them every once in a while in the winter. They aren’t a bird you’re guaranteed to see at your feeder, so when it happens, people get excited, and they want to know what they’re looking at.

Assistant professor Scott Taylor, Co-author
Department of Ecology and Evolutionary Biology
University of Colorado, Boulder, CO, USA
And, something which should embarrass any Creationist with sufficient knowledge to understand its significance in terms of their dogmas that mutations are invariably detrimental and that no new information can be created by mutation, part of the DNA which includes this 'super gene' is inverted in some forms.

As the University of Colorado, Boulder news release explains:
These new findings picked up where that previous research left off, with Erik Funk, an EBIO PhD student at CU Boulder and the lead author of the paper, going back and re-examining the original samples and adding a few more from other areas, including Greenland, Iceland and parts of Europe, to get a more complete picture.

Altogether, Funk examined the full genome of 73 individuals from all the different subtypes, including the Common Redpoll, the Hoary Redpoll, and the Lesser Redpoll.

What he found is that, despite the differences in appearance, the birds are almost identical genetically but with a “supergene” that controls the different traits that make the birds appear different. In particular, the researchers found a chromosomal inversion, or when part of the chromosome is flipped, for one of the chromosomes, that allowed this supergene to get created.
Often times we assume that a lot of traits can act independently, meaning that different traits can be inherited separately from one another, but this particular result shows that sometimes these traits are actually tightly linked together. … At least for these birds, they’re inheriting a whole group of traits together as one.

It seems to be less common, but I think one of the things that we are learning as we have access to more sequence data now is that maybe [supergenes are] not as uncommon as we once thought.

Sometimes birders get mad if you take birds off their list, but I think it makes the Redpolls even more interesting. Understanding the genetic basis of the trait makes it make much more sense now, which I think is pretty cool.

Erik Funk, Lead author
PhD Student
Department of Ecology and Evolutionary Biology
University of Colorado, Boulder, CO, USA
A supergene is a group of genes closely linked on a chromosome, so they tend to be inherited together and to be conserved over time, to give clusters of morphologies which tend to occur together, giving the appearance of different species while the overall variation in DNA is very small.

At some point in the evolution of this species, the part of its DNA which happens to contain the cluster of linked genes became inverted, the result is a complex of different forms which look like different species especially since different plumages, colour, size and shape of bill, etc, tend to occur together, while even within what looked like a species, the range is considerable. But in fact these were all the same species, able to interbreed and produce a whole range of morphologies.

There was, of course, no new information created or destroyed by this simple inversion and no detriment to it carriers, so nothing that could be regarded as 'devolutionary' - which the Deception Institute is now trying to foist on its scientifically illiterate target audience to discredit the TOE, but which to anyone with even a basic understanding of the TOE makes no sense at all because detrimental mutations will be quickly removed from the species gene pool by natural selection. And manifestly, these changes in genetic information in the Redpoll were retained.

In the abstract to their open access paper in Nature Communications the authors say:
The genetic architecture of a phenotype can have considerable effects on the evolution of a trait or species. Characterizing genetic architecture provides insight into the complexity of a given phenotype and, potentially, the role of the phenotype in evolutionary processes like speciation. We use genome sequences to investigate the genetic basis of phenotypic variation in redpoll finches (Acanthis spp.). We demonstrate that variation in redpoll phenotype is broadly controlled by a ~55-Mb chromosomal inversion. Within this inversion, we find multiple candidate genes related to melanogenesis, carotenoid coloration, and bill shape, suggesting the inversion acts as a supergene controlling multiple linked traits. A latitudinal gradient in ecotype distribution suggests supergene driven variation in color and bill morphology are likely under environmental selection, maintaining supergene haplotypes as a balanced polymorphism. Our results provide a mechanism for the maintenance of ecotype variation in redpolls despite a genome largely homogenized by gene flow.

The significance of this discovery of the role of these tightly-linked supergenes is that they could help to resolve the many confusing complexes of closely-related species that often seem to form an interbreeding 'superspecies', making precise taxonomic classification difficult or impossible. These complexes are often found in birds, insects, reptiles and plants.

Thank you for sharing!

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