Evolution in action in reverse

[Dymanic]

Engineering turns two species back into one (http://www.nature.com/nsu/030303/030303-5.html)

Scientists have turned two species back into one by shuffling parts of chromosomes. The achievement demonstrates that genome rearrangements can drive species apart.

"This is a very different approach to understanding evolution," says evolutionary geneticist Cliff Zeyl of Wake Forest University in Winston-Salem, North Carolina. Instead of trying to encourage the development of a new species in the lab, Oliver's group manipulated the yeast chromosomes to see if at some point the two species might have been one.

[arcticpenguin]

My, but that "Intelligent Designer" sure was sloppy.

[BillHoyt]

Originally posted by Dymanic
Engineering turns two species back into one (http://www.nature.com/nsu/030303/030303-5.html)

Scientists have turned two species back into one by shuffling parts of chromosomes. The achievement demonstrates that genome rearrangements can drive species apart.

"This is a very different approach to understanding evolution," says evolutionary geneticist Cliff Zeyl of Wake Forest University in Winston-Salem, North Carolina. Instead of trying to encourage the development of a new species in the lab, Oliver's group manipulated the yeast chromosomes to see if at some point the two species might have been one.

Soooo cool! Thanks for that great link, Dynamic.

Cheers,

[Crossbow]

Maybe we can that 'Pig-Elephant' one day after all!

[a fantoche de meia]

"This study is very elegant," agrees Ken Wolfe of the University of Dublin, who works on evolution at the molecular scale. "But there is still a long way to go to explain where these species come from." The hybrids' low fertility rate would prevent them from surviving as a species in the wild.


I don't see why that would be a problem. Yeast can reproduce asexually by budding, can't they?

[a fantoche de meia]

Originally posted by Crossbow
Maybe we can that 'Pig-Elephant' one day after all!
That wouldn't be kosher.

[Dymanic]

This subject fascinates me, and I'm working hard to get up to speed. This is made difficult by the fact that it seems that for every new revelation I encounter, I encounter an opposing viewpoint from an equally credible source. It doesn't look like the debates around the importance of drift, or around P.E vs. Gradualism are going to be resolved anytime soon.

I've just found this in Reinventing Darwin by Niles Eldredge:

"We are seeing, I firmly believe, only successful speciation events. Consider the common fate of fledgling species. I was, as a student in the 1960's, immensely influenced by the work of University of California (Berkely) botanist Harlan Lewis. Lewis worked on the genetics of the plant genus Clarkia. In some populations he discovered that a fairly severe mutation occurred at sufficiently high frequencies, that each year some small populations would be established that were reproductively disjunct--isolated--from the parental species populations. Instant speciation (although I remain content with the "five to fifty thousand year" estimate, which is by far the more usual rate--a rate that only looks fast when viewed agains the enormity of true evolutionary time)."

He goes on from there to say that extinction was the fate for all of these Clarkia populations, because although they were reproductively isolated from the parental species, they were numerically swamped by the parent species because they were adaptively identical--the main point being that had they been sufficiently different from the parent stock, they might have survived as a new species.

This looks like a mechanism that would support the possibility of (gasp--can barely force myself to say it--single step speciation).

I'm inclined to approach the idea of single-step speciation with considerable caution, but I'm finding this (along with the rest of what Eldredge has presented) to be a rather compelling argument for speciation as a cause, rather than a result of adaptive change.

I feel like I should ask somebody to talk me out of it.

[arcticpenguin]

That sort of single-step speciation, if it happened, would never be recognized in the fossil record because the new species looks just like the old one. Also, the time resolution of the fossil record is not adequate to distinguish an overnight event from on that took 50,000
years.

This is the kind of topic that can give you many interesting ideas, but then you should go back over them to see how many of them actually make sense.

[a fantoche de meia]

Originally posted by Dymanic

Scientists have turned two species back into one by shuffling parts of chromosomes. The achievement demonstrates that genome rearrangements can drive species apart.

If they could do this a few billion more times, we could find out what the first cell looked like.

[Kiri]

Originally posted by o fantoche de meia

That wouldn't be kosher.

...And not nearly as much fun as doing it the old-fashioned way.

[Dymanic]

That sort of single-step speciation, if it happened, would never be recognized in the fossil record because the new species looks just like the old one.
Yes, that's one of the points Eldredge makes.

It also makes me wonder how hard it would be to go out in the field and find groups of organisms that appear to be single species, and yet are reproductively disjunct due to this kind of difference at the genetic level.

I saw an article in Smithsonian (last October?) about a lady in Arizona who was studying what looked like a speciation event in progress in some walking-stick insects she found in her backyard. The discussion was around mate-recognition between two varieties that were somewhat dissimilar, yet still interbreeding.

But it's not only paleontologists who would be unable to tell one from the other; neither would other members of their own, or the parent species, and neither would natural selection.

So these new guys would be mating all the time, but chances are most of the matings would be with members of the parent species, with whom they were not fertile. Members of the parent species wouldn't have this problem, and so would overwhelm them reproductively--this is what was observed in all of the new Clarkia species, and I take it that the PE model uses this to help explain the stasis they see in the fossil record.

All it takes is that the new species be different (not necessarily better, just different) for it to survive.

This is the kind of topic that can give you many interesting ideas, but then you should go back over them to see how many of them actually make sense.
Yes, that's really just the trick, isn't it? The problem I have is that, taken one at a time, they all seem to make sense -- but they don't all agree!

[arcticpenguin]

In the yeast article, they don't mention an estimate for how long ago the two species diverged. It should be possible to estimate that based on genetic drift.

[BillHoyt]

Originally posted by Dynamic:
This looks like a mechanism that would support the possibility of (gasp--can barely force myself to say it--single step speciation).
Originally posted by ArcticPenguin:
That sort of single-step speciation, if it happened, would never be recognized in the fossil record because the new species looks just like the old one. Also, the time resolution of the fossil record is not adequate to distinguish an overnight event from on that took 50,000 years.
Polyploidy is just such a single step speciation event that might be evident in the fossil record. The polyploid cousins of diploid plants are often significantly larger.

Another single-step speciation event is taking place in a Japanese pond near a nylon factory. There a bacterium had a simple mutation that gave it the ability to digest nylon monomer. Over time, sufficient other mutations will occur in this line so that it will be considered a new species. The fossil record would probably never show this, though, because it is morphologically identical with its cousins.

Cheers,

[Agammamon]

Originally posted by arcticpenguin
My, but that "Intelligent Designer" sure was sloppy.

Nah, the ID proponents will use this as an example of the code reuse techniques that programmers use therefore it must be evidence of intelligence.