wow! - new macro-evolved structures in lizards in just 37 years

[foofighter]

http://www.sciencedaily.com/releases/2008/04/080417112433.htm

 

 

seems pretty awesome doesn't it?

[Realitycheck]

Tail clips taken for DNA analysis confirmed that the Pod Mrcaru lizards were genetically identical to the source population on Pod Kopiste.

 

Observed changes in head morphology were caused by adaptation to a different food source.

 

“What is unique about this finding is that rapid evolution can affect not only the structure and function of a species, but also influence behavioral ecology and natural history,” says Irschick.

 

It doesn't make a lot of sense. What is evolution without genetic mutation?

[foofighter]

i think they mean it has retained enough genetic similarity to still remain part of the parent species - they don't mean that the genetic analysis was 100% identical. that's what it would seem to mean, imho

[CaptainPanic]

From original article: Analysis of the stomach contents of lizards on Pod Mrcaru showed that their diet included up to two-thirds plants, depending on the season, a large increase over the population of Pod Kopiste.

 

“As a result, individuals on Pod Mrcaru have heads that are longer, wider and taller than those on Pod Kopiste, which translates into a big increase in bite force,” says Irschick.

 

Seems to me that the phenotype changed due to a different diet. That is not genetic. The test they should do now is to place the lizards from the 2nd island back on the first island, and see if the new generation born from those individuals looks different (that could be genetic).

 

Alternatively, I think in 2008 it is not too hard to simply map all genes, and see if there's a difference.

 

Evolution is a change in the inherited traits. Imho that means it is genetic.

[foofighter]

if the phenotype is due to a different diet, that's because such genetic variation is selected for. the heads don't just grow in response to a different diet, that would be Lamarckism

[CharonY]

Alternatively, I think in 2008 it is not too hard to simply map all genes, and see if there's a difference.

 

Sequencing an eukaryote, is still awfully expensive and time consuming (and identification of genes is even worse). After skimming over it I could not see any reference whether the morphological changes are at some point genetic. This is btw. quite interesting. According to the Darwinian theory of evolution (remember, Darwin knew nothing about genes) this would be an example of adaptive evolution. However according to modern synthesis it would not. It would be interesting to breed them with a different diet, though.

 

if the phenotype is due to a different diet, that's because such genetic variation is selected for. the heads don't just grow in response to a different diet, that would be Lamarckism

It would only be lamarckism if the traits are becoming inheritable regardless of diet.

[CDarwin]

It doesn't make a lot of sense. What is evolution without genetic mutation?

 

The majority of variability in sexually reproducing populations comes from recombination, not mutation. I don't know that that's the case here, though. I think they did just mean that they stayed the same species. After all no two individuals are ever actually "genetically identical."

 

That wouldn't be "macro-evolutionary," then, though.

[Mr Skeptic]

I agree, no macroeveolution going on here. Especially if they stay the same species:doh::doh:

[foofighter]

i wasn't referring to a species change. i was referring to the development of new organs in the species introduced to the new island. if that's not macro, how do you explain that via micro?

[Aardvark]

Macro/Micro is a false distinction propagated by creationists.

 

Either there is genetic change happening or there is not, that is the sole criteria that needs to be looked at.

[PhDP]

Macro/Micro is a false distinction propagated by creationists.

 

...not really. Many scientists use this distinction, especially those studying development and molecular genetics.

[iNow]

Well, that sounds kind of silly, since "macro" is just a collection of a whole bunch of "micro."

[CharonY]

Not really, it is just another layer of complexity. For example, humans are nothing more than a bunch of cells, too. Yet a cell line is something different than a complete human.

[CDarwin]

i wasn't referring to a species change. i was referring to the development of new organs in the species introduced to the new island. if that's not macro, how do you explain that via micro?

 

"Microevolution" is really just another word for evolution. It's the process evolution takes, gradually and by mixing up the allele frequencies in populations. "Macroevoltion" is a term applied retrospectively to any evolutionary event yielding a new lineage. In the purest sense this is simply speciation, but the word is also used to refer to the origin of larger groups like phyla. If course, the origin of any larger group begins with speciation.

[lucaspa]

It doesn't make a lot of sense. What is evolution without genetic mutation?

 

That's because the paper didn't look at nuclear genes. The full paper is here: http://www.pnas.org/cgi/content/full/105/12/4792

 

"Genetic mitochondrial DNA analyses indicate that the lizards currently on Pod Mraru are indeed P. sicula and are genetically indistinguishable from lizards from the source population"

 

So the mtDNA didn't change. We wouldn't expect it too. I'm afraid that part of the NewScientist article was misleading. There could be lots of changes in the nuclear genes. What the scientists were trying to establish by looking at the mtDNA was that the lizards did indeed come from the population they seeded and the mtDNA was the best way to demonstrate it precisely because it would not change. The authors were eliminating the hypothesis that the lizards are the descendents of another species that accidentally colonized the island.

 

We don't know if there is a new species. No breeding experiments were conducted. So we don't know if the new population can interbreed with the old. I wish they had done that.

[CharonY]

Yes, however the authors also did not show that the observed changes were inheritable. Of course, these extreme changes are unlikely merely the result of diet changes, but as far as I can see it has not been unequivocally established. Also I think that the author's use of macroevolution might be not that one defined as evolution at or above the species level. In the reference they cited the following statement is found:

"Historically, macroevolution has been equated with substantive adaptive change, and rapid and fluctuating evolution has been regarded as evolutionary noise. Thus, debate continues over what constitutes trivial versus important evolution. We argue that the real distinction between macro- and microevolution may lie only in the degree to which the factors causing evolution are fluctuating or are gradually and persistently directional, and not in the ecological significance of that evolution."

 

The observed adaptation (if genetically based) would likely fit into this particular definition. Of course, the authors only implied that their work is an example of macroevolution (and that only briefly in the introduction), but i guess that is what the New Scientist took up and beefed up a bit.

[CDarwin]

Uhm, it wasn't a New Scientist article that was linked to. It was Science Daily, which is a web-based science news service with no connection to the New Scientist, as far as I am aware.

[lucaspa]

Yes, however the authors also did not show that the observed changes were inheritable.

 

For the changes not to be heritable you would need this particular generation only to have the changes. Taking a random sample of the population -- of all ages (which they did) -- falsifies that. The only way the changes could have gotten to this generation was to be inherited from previous generations.

 

Of course, these extreme changes are unlikely merely the result of diet changes, but as far as I can see it has not been unequivocally established. Also I think that the author's use of macroevolution might be not that one defined as evolution at or above the species level. In the reference they cited the following statement is found:

"Historically, macroevolution has been equated with substantive adaptive change, and rapid and fluctuating evolution has been regarded as evolutionary noise. Thus, debate continues over what constitutes trivial versus important evolution. We argue that the real distinction between macro- and microevolution may lie only in the degree to which the factors causing evolution are fluctuating or are gradually and persistently directional, and not in the ecological significance of that evolution."

 

Yes, it appears that the authors are attempting to change the definition. In their view, if the beech trees would not have become white again, the change in coloration of the peppered moth would have been "macroevolution". But because the environment fluctuated, the change also fluctuated. I haven't found any other evolutionary biologists who have stated this view of macroevolution. "Persistently directional" selection will give new species because some alleles are fixed and others are lost -- thus the population changes its allele constitution. However, that alone won't make a new species. You need enough change to have reproductive isolation.