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Speciation 
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Post Speciation
I almost hijacked an old thread for this, since I'm not sure that it is worth a discussion. But I was pretty jazzed by some news in the latest Economist about the importance of hybridization in speciation. Apparently what was known to occur already among microbes has now been found in, of all places, one of the species of birds included as "Darwin's Finches" in the Galapagos. The phenomenon is that mating between related species occurs, and generates, probably, a new species.

The article has a really good readout from the research that has emerged about hybridization and speciation in complex animals (plants are, apparently, a different kettle of, well, fish) and it isn't clear that the Galapagos example is anything like the original observation. It just makes a good hook.

https://www.economist.com/science-and-t ... ary-theory

What caught my eye was the demotion of mutation as a driver for evolution. The original Darwinian formulation, and therefore the textbook version when I was in school, was that the raw material of selection is entirely due to mutation. Probably because I read a lot of Stephen Jay Gould's stuff, who is a skeptic of the mutation-as-driver model, I have long thought it was unrealistically slow. The article gives the example of cichlids in Lake Victoria, which was non-existent as little as 15,000 years ago but now has 500 species of cichlids living within, as evidence that hybridization plays an important role in the radiation of new species within a new niche. Interesting stuff.



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geo, Murmur
Sun Oct 04, 2020 3:26 pm
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Post Re: Speciation
Harry Marks wrote:
I almost hijacked an old thread for this, since I'm not sure that it is worth a discussion. But I was pretty jazzed by some news in the latest Economist about the importance of hybridization in speciation. Apparently what was known to occur already among microbes has now been found in, of all places, one of the species of birds included as "Darwin's Finches" in the Galapagos. The phenomenon is that mating between related species occurs, and generates, probably, a new species.


I've been meaning to check in on this thread. It's a very interesting article to be sure. The role of hybridization in evolution is very cool. I did some research last year into the Carolina Chickadee and its close relative, the Black-capped chickadee. The two species interbreed, but only in a narrow band of territory where their habitats overlap. This narrow band does fluctuate quite a lot, and probably has shifted north as climate changes. I was convinced for a time that I was seeing some of the hybrids in Franklin, NC, where we used to live. Alas, it was all very inconclusive, and now we live in Maryland.

The article suggests hybridization was probably a factor with the evolution of homo sapiens, that there was a gene flow between several early hominids, which might potentially answer a lot of questions about our origins. As the author says, "To be human, then, is to be a multispecies mongrel."

Hybridization is also another example of how evolutionary theory continues to evolve well beyond Darwin's original framework. I don't think it's really a surprise to anyone that evolutionary theory is more complex than Darwin envisaged. Of course, I've also read a lot of Stephen Jay Gould, and that helped me understand that there are probably many mechanisms that drive speciation, perhaps many still not very well understood.

By the way, the article inspired me to subscribe to The Economist. So thanks for that!


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Harry Marks
Thu Nov 05, 2020 9:31 pm
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Post Re: Speciation
geo wrote:
The role of hybridization in evolution is very cool. I did some research last year into the Carolina Chickadee and its close relative, the Black-capped chickadee. The two species interbreed, but only in a narrow band of territory where their habitats overlap. This narrow band does fluctuate quite a lot, and probably has shifted north as climate changes. I was convinced for a time that I was seeing some of the hybrids in Franklin, NC, where we used to live. Alas, it was all very inconclusive, and now we live in Maryland.
I'm impressed that you have actually crossed paths with some of these matters.

geo wrote:
The article suggests hybridization was probably a factor with the evolution of homo sapiens, that there was a gene flow between several early hominids, which might potentially answer a lot of questions about our origins. As the author says, "To be human, then, is to be a multispecies mongrel."
Yes, I found that intriguing. The very concept of species turns out to have a porous boundary, which strikes me as likely given what we know, and how much we don't know, about DNA replication.

geo wrote:
By the way, the article inspired me to subscribe to The Economist. So thanks for that!
I think you will be glad of the choice. There is an article in today's edition about superbatteries that I found fascinating. What is a superbattery? Well, it's a cross between a supercapacitor and a battery. "The battery serves as a marathon runner, providing a steady discharge over a long distance. The supercapacitor is a sprinter, unleashing a large amount of energy rapidly." I love that they go to the trouble to formulate relatable imagery, to communicate effectively to those of us with just a passing acquaintance.



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Sat Nov 07, 2020 10:47 pm
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