Two species of crow evolving ...

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Two Species of Crow Are Evolving Before Our Eyes in Europe
MICHELLE STARR
29 MAR 2019

Two European crows that look quite different from each other are actually diverging from a single species, right before our eyes. In Western Europe, it's the inky-black carrion crow (Corvus corone). In the east, the grey hooded crow (C. cornix).

They overlap in a very narrow zone running along the River Elbe in Germany, where they sometimes mate with each other to produce fertile hybrids - a strange result, since many species hybrids are infertile.

Now, genomic analysis has revealed that C. corone and C. cornix are actually almost indistinguishable from a genetic standpoint. The only significant genetic difference between them can be found in the gene responsible for colouration.

"Defining speciation as the buildup of reproductive isolation, carrion crows and hooded crows are in the process of speciation," said evolutionary biologist Jochen Wolf of Ludwig-Maximilians-Universität in Munich.

Exactly what was keeping the two populations apart was unclear - so Wolf and his colleagues performed genetic analyses of around 400 birds. These were selected from within the hybrid zone, as well as the zones on either side, where the species' territories don't overlap.

"Only two major effect genes which together encode the feather colour differ sharply on either side of the hybrid zone - the gray alleles are not found to the west of the zone and the black allele is absent in the eastern region," Wolf said.

"That's a very strong indication that there is rigorous selection on the basis of colour."

This suggests the crows are choosing mates based on colour. Birds of a feather literally, in this instance, flock together - carrion crows prefer black mates and hooded crows prefer grey ones.

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Sexual selection.

Enjoy

Thread copied here from the Two species of crow evolving ... thread in the Proposed New Topics forum.

An interesting article RAZD.

I didn't come to appreciate sexual selection as a mechanism of evolution separate from natural selection until I read The Evolution of Beauty: How Darwin's Forgotten Theory of Mate Choice Shapes the Animal World—And Us by Richard O. Prum.

From Goodreads:

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A major reimagining of how evolutionary forces work, revealing how mating preferences--what Darwin termed "the taste for the beautiful"--create the extraordinary range of ornament in the animal world.

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In the great halls of science, dogma holds that Darwin's theory of natural selection explains every branch on the tree of life: which species thrive, which wither away to extinction, and what features each evolves. But can adaptation by natural selection really account for everything we see in nature?
Yale University ornithologist Richard Prum--reviving Darwin's own views--thinks not. Deep in tropical jungles around the world are birds with a dizzying array of appearances and mating displays: Club-winged Manakins who sing with their wings, Great Argus Pheasants who dazzle prospective mates with a four-foot-wide cone of feathers covered in golden 3D spheres, Red-capped Manakins who moonwalk. In thirty years of fieldwork, Prum has seen numerous display traits that seem disconnected from, if not outright contrary to, selection for individual survival. To explain this, he dusts off Darwin's long-neglected theory of sexual selection in which the act of choosing a mate for purely aesthetic reasons--for the mere pleasure of it--is an independent engine of evolutionary change.
Mate choice can drive ornamental traits from the constraints of adaptive evolution, allowing them to grow ever more elaborate. It also sets the stakes for sexual conflict, in which the sexual autonomy of the female evolves in response to male sexual control. Most crucially, this framework provides important insights into the evolution of human sexuality, particularly the ways in which female preferences have changed male bodies, and even maleness itself, through evolutionary time.
The Evolution of Beauty presents a unique scientific vision for how nature's splendor contributes to a more complete understanding of evolution and of ourselves.

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The usual mountain out of a molehill or evolution out of mere variation. Yes sexual selection. Microevolution. Separate populations defined by feather color. Microevolution. To call it speciation is to indulge in the usual self deception that keeps the ToE fantasy alive.

Sexual selection is completely natural, so couldn't it be just one type of natural selection? There could be natural selection by food source, by terrain, by weather variations, by sexual cues, etc.

--Percy

Sexual selection is completely natural, so couldn't it be just one type of natural selection?

That is what I thought also.

There could be natural selection by food source, by terrain, by weather variations, by sexual cues, etc.

Natural selection has a positive feedback loop that means increased frequency of certain alleles in a population and there may be a negative feedback loop decreases the frequency of others. We think of this as fit and less fit, when considering competition within a species or population, but it also can impact competition between species and whether one thrives and another goes extinct.

Prum lays out a really compelling argument with many, many examples where characters are selected, usually by females, that have no positive effect on fitness. These characters can be appearance, behaviors or calls and are often combinations of features.

I was quite surprised to have to revise my view on this topic.

Natural selection has a positive feedback loop that means increased frequency of certain alleles in a population and there may be a negative feedback loop decreases the frequency of others.

Of course. The black feathered population has more alleles for black feathers, and probably lots of homozygosity for black feathers at the feather loci too, while the grey population has more alleles for grey feathers and the same genetic situation. The black feathered population has correspondingly fewer alleles for grey feathers, which will eventually decrease to zero as reproductive isolation continues, and the grey population for black feathers. This ought to be elementary my dear Watson, but evo theory manages to complicate the simplest things.

And of course it makes sense to categorize sexual selection as a type of natural selection, just as I've argued that geographic isolation is a form of natural selection too, as it isolates some particular collection of alleles and breeds them together to produce a new phenotype, which is all any selective process does.

And again, all this is within microevolution, it's ridiculous to make the arbitrary fact that the two populations don't interbreed into "speciation." It's nothing but two variations that happen to separate, and may possibly have a genetic barrier to interbreeding although that is not necessary. If it does it could be because of the greater homozygosity of the characteristic feather color in each population and the more fixed loci each has the less ability to combine the two.

Edited by Faith, : No reason given.

This ought to be elementary my dear Watson, but evo theory manages to complicate the simplest things.

Yep, facts and evidence are just so complicated.

And of course it makes sense to categorize sexual selection as a type of natural selection

And of course, you don't have a fucking clue what you are talking about.

And again, all this is within microevolution, it's ridiculous to make the arbitrary fact that the two populations don't interbreed into "speciation."

Oh ok, I'll send out an alert right away that a YEC is making up a new rule. You should expect action soon.

It's nothing but two variations that happen to separate, and may possibly have a genetic barrier to interbreeding although that is not necessary. If it does it could be because of the greater homozygosity of the characteristic feather color in each population and the more fixed loci each has the less ability to combine the two.

Right, so you're just winging it, so to speak?

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The usual mountain out of a molehill or evolution out of mere variation. Yes sexual selection. Microevolution. Separate populations defined by feather color. Microevolution. To call it speciation is to indulge in the usual self deception that keeps the ToE fantasy alive.

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There is a lot of arrogant bluster there but no reason why this should not be considered an example of speciation in progress.

In fact the reality of two closely related - but easily distinguished - populations occupying different geographical regions - despite the lack of geographical barriers is reason enough to suspect that something of the sort is happening. That has been known for some time (it is also true in Britain). Steve Jones discusses it in Almost Like a Whale (aka Darwin’s Ghost)

I suppose that I should add the point that these crows have been considered separate species for a long time. The only new stuff is the genetic analysis - which includes evidence of selection.

Edited by PaulK, : No reason given.

I didn't come to appreciate sexual selection as a mechanism of evolution separate from natural selection until I read The Evolution of Beauty: How Darwin's Forgotten Theory of Mate Choice Shapes the Animal World—And Us by Richard O. Prum.

My pet theory is that sex is what has lead to increased intelligence in humans via more and more complex mating displays/rituals/song and dance.

I also see sexual selection as a mechanism for creating stasis in a breeding population in a stable ecology.

Mate selection operates at every mating opportunity, and thus can operate at a faster rate than other forms of natural selection in causing or suppressing changes to the breeding population.

See Sexual Selection, Stasis, Runaway Selection, Dimorphism, & Human Evolution

Enjoy

I thought you ran away.

From A test for claimed knowledge of how macroevolution occurs, Message 705:

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Defining a species

... Hooded crows and carrion crows look different, and largely mate within their own groups — but in some areas, they hybridize. Should they be considered the same species or separate species?

If two lineages of oak look quite different, but occasionally form hybrids with each other, should we count them as different species? There are lots of other places where the boundary of a species is blurred. It's not so surprising that these blurry places exist — after all, the idea of a species is something that we humans invented for our own convenience!

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Classification is for our use in discussions, and they are subject to change when information provides new insights.

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Carrion Crow: Distribution and genetic relationship to hooded crows

The carrion crow (Corvus corone) and hooded crow (Corvus cornix, including its slightly larger allied form or race C. c. orientalis) are two very closely related species[7] whose geographic distributions across Europe are illustrated in the accompanying diagram. It is believed that this distribution might have resulted from the glaciation cycles during the Pleistocene, which caused the parent population to split into isolates which subsequently re-expanded their ranges when the climate warmed causing secondary contact.[8][9]

A map of Europe indicating the distribution of the carrion and hooded crows on either side of a contact zone (white line) separating the two species

Poelstra and coworkers sequenced almost the entire genomes of both species in populations at varying distances from the contact zone to find that the two species were genetically identical, both in their DNA and in its expression (in the form of mRNA), except for the lack of expression of a small portion (<0.28%) of the genome (situated on avian chromosome 18) in the hooded crow, which imparts the lighter plumage colouration on its torso.[8] Thus the two species can viably hybridize, and occasionally do so at the contact zone, but the all-black carrion crows on the one side of the contact zone mate almost exclusively with other all-black carrion crows, while the same occurs among the hooded crows on the other side of the contact zone.

It is therefore clear that it is only the outward appearance of the two species that inhibits hybridization.[8][9] The authors attribute this to assortative mating (rather than to ecological selection), the advantage of which is not clear, and it would lead to the rapid appearance of streams of new lineages, and possibly even species, through mutual attraction between mutants. Unnikrishnan and Akhila propose, instead, that koinophilia is a more parsimonious explanation for the resistance to hybridization across the contact zone, despite the absence of physiological, anatomical or genetic barriers to such hybridization.[8]

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Also see Two species of crow evolving ... on this possible crow speciation in process, apparently due to coloration:

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"Only two major effect genes which together encode the feather colour differ sharply on either side of the hybrid zone - the gray alleles are not found to the west of the zone and the black allele is absent in the eastern region," Wolf said.

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Breeding populations apparently separated by sexual/mate selection.

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Koinophilia is an evolutionary hypothesis proposing that during sexual selection, animals preferentially seek mates with a minimum of unusual or mutant features, including functionality, appearance and behavior.[1][2][3][4][5][6] Koinophilia intends to explain the clustering of sexual organisms into species and other issues described by Darwin's Dilemma.[3][4][5] The term derives from the Greek, koinos, "common", "that which is shared", and philia, "fondness".

Natural selection causes beneficial inherited features to become more common at the expense of their disadvantageous counterparts. The koinophilia hypothesis proposes that a sexually-reproducing animal would therefore be expected to avoid individuals with rare or unusual features, and to prefer to mate with individuals displaying a predominance of common or average features. ...

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This Koinophilia is similar to what I proposed for sexual selection in Sexual Selection, Stasis, Runaway Selection, Dimorphism, & Human Evolution and my discussion on the causes of stasis in breeding populations living in stable ecological habitats.

This Crow mate selection is similar to the overlap of the end of ring species like the Greenish Warbler, another place where the definition of species is problematic.

Of course. The black feathered population has more alleles for black feathers, and probably lots of homozygosity for black feathers at the feather loci too, while the grey population has more alleles for grey feathers and the same genetic situation. The black feathered population has correspondingly fewer alleles for grey feathers, which will eventually decrease to zero as reproductive isolation continues, and the grey population for black feathers. This ought to be elementary my dear Watson, but evo theory manages to complicate the simplest things.

What is complicated in this by "evo theory" when they are saying the same thing?

And of course it makes sense to categorize sexual selection as a type of natural selection, just as I've argued that geographic isolation is a form of natural selection too, as it isolates some particular collection of alleles and breeds them together to produce a new phenotype, which is all any selective process does.

Indeed, but sexual/mate selection explains observations that seem to be at odds with survival (peacocks) and why populations tend towards stasis in stable ecological environments/habitats.

And again, all this is within microevolution, it's ridiculous to make the arbitrary fact that the two populations don't interbreed into "speciation." It's nothing but two variations that happen to separate, and may possibly have a genetic barrier to interbreeding although that is not necessary. ...

Of course it is microevolution -- that's where all evolutionary change occurs, within the breeding population/s. Macroevolution is just microevolution over many generations with the accumulation of changes making descendant populations different from ancestral populations.

Speciation is one of the observed elements of macroevolution when two daughter populations are isolated over generations, allowing different microevolutionary paths to be taken by the daughter populations until they differ from one another. The crows are evidence of this difference in results of microevolution over generations.

Lack of interbreeding is the definition of species, so when this happens it is logical to call that a speciation event.

... If it does it could be because of the greater homozygosity of the characteristic feather color in each population and the more fixed loci each has the less ability to combine the two.

Indeed, the two populations have diverged from one another genetically, and this has resulted in the apparent speciation event in progress.

Whether you like it or not, this is how biology defines species and speciation events.

Enjoy

So this is "micro-evolution" stuff.

Back to macro-evolutionary stuff.

Am I correct in my memory when I recall many creationists admitting that early birds have features common with reptiles? (usually saying God creates features that are "intermediate")