Speedy evolution of a slow lizard.

[espritch]

I came across an article (http://dsc.discovery.com/news/2008/03/24/tuatara-evolution.html) indicating that those peculiar lizard like New Zealand reptiles called tuataras have the fastest molecular evolution of any species yet measured. What is peculiar about this is that they show very little evidence of morphological evolution.

Although the discovery about the tuatara's speedy evolution goes against conventional wisdom, it supports a prediction made 40 years ago by evolutionary biologist Allan Wilson of New Zealand, who supported the then-controversial notion that "the rate of molecular evolution was uncoupled from the rate of morphological [body shape] evolution."

So why would morphological and molecular evolution be uncoupled? And why would a slow breeding cold blooded reptile exhibit such a rapid rate of molecular evolution? This seems quite counter intuitive to me.

[ck1]

I also came across this story today, and was intrigued by the conclusion that the evolution of phenotype is "uncoupled" from molecular evolution.

I noticed this story because of an earlier thread on this forum about the apparent phenotypic stasis in some lineages - like horseshoe crabs, sharks, and cockroaches. These investigators were able to do some sequence comparisons using mitochondrial DNA isolated from modern and fossil specimens. The estimated rate of evolution in the segments they looked at was a order of magnitude greater than the rate estimated in any other lineage.

http://talkrational.org/showpost.php?p=14249&postcount=72

[espritch]

I had thought about posting this in the Horseshoe Crab thread since it seems germane, but I thought it was worth it's own thread.

[ck1]

I had thought about posting this in the Horseshoe Crab thread since it seems germane, but I thought it was worth it's own thread.

Yes, this is getting a fair bit of press. Would be worth getting some opinions here as to its significance.

[Dlx2]

What evidence exists to suggest that Sphenodon is completely unchanged across hundreds of millions of years? I'm under the impression that rhynchocephalians have actually experienced a hell of a lot of evolution.

But then, I work on lungfish, and hearing them called "living fossils" pisses me off, too.

[llanitedave]

Well, there's no reason why morphology and overall genetic change should be coupled, since the genes controlling morphology are a very small percentage of the overall genome. If stabilizing selection is in effect, that wouldn't necessarily stabilize very many genes.

And as Dlx2 says, all that's really being conserved is the general structure of the group. There's a lot of room for variation in individual features that would not change the overall or defining rhynchocephalian metastructure.

[Ray Moscow]

The Ancestor's Tale a similar note about alligators having a fast rate of molecular/genetic evolution. I too found it puzzling, since crocodiles seem pretty much unchanged morphologically since the dinosaur days.

[Dlx2]

I too found it puzzling, since crocodiles seem pretty much unchanged morphologically since the dinosaur days.

My girlfriend studies crocodile evolution. There is nothing that pisses her off more than the statement "crocodiles haven't changed since the dinosaurs."

[ck1]

My girlfriend studies crocodile evolution. There is nothing that pisses her off more than the statement "crocodiles haven't changed since the dinosaurs."

The Sphenodon study analyzed mtDNA sequences from extant and fossil specimens. Has the same thing been done with crocodiles (or horseshoe crabs)?

[Dlx2]

The Sphenodon study analyzed mtDNA sequences from extant and fossil specimens. Has the same thing been done with crocodiles (or horseshoe crabs)?

Not sure. I know that there's significant phenotypical change in all three groups.

[Ray Moscow]

My girlfriend studies crocodile evolution. There is nothing that pisses her off more than the statement "crocodiles haven't changed since the dinosaurs."

My view was no doubt clouded by my ignorance of ancient crocodiles.

Perhaps she could post some overview of the major differences between the ancient and modern species?

This little article (http://www.essortment.com/all/crocodilehistor_rhut.htm)mentions some of the main points.