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Lizards “evolve” in just a few months?


This one is a few years old but the “evolution” of the lizard icicle is still worth recounting for what it shows about what the word is often taken to mean:

We may complain about freezing temperatures, but most cold snaps leave us little worse for the wear. That’s not the case for a common lizard living on the Texas-Mexico border, which, in just the span of a few months, underwent a dramatic genetic transformation in response to cold weather. In fact—in one of the most detailed examples of rapid evolution to date—a new study shows that just one cold snap can change the way green anoles’ muscular and nervous systems respond to temperature.

“It’s a very conclusive instance of rapid evolution,” says Charles Brown, a behavioral ecologist at the University of Tulsa in Oklahoma, who was not involved with the work. The study, he says, is “one of the only real examples in which the genetic mechanisms behind these rapid evolutionary events have been shown.” And Michael Logan, an evolutionary ecologist at the Smithsonian Tropical Research Institute in Panama City, calls the work “the most comprehensive demonstration of natural selection to date” on how body temperature is regulated…

But as Butch Brodie, director of the University of Virginia Mountain Lake Biological Station in Pembroke points out, it’s not clear whether evolution will continue to push the lizards to be ever more cold tolerant. “The temptation from results like these is to assume extreme events drive much of evolutionary change, but it may not be that simple,” he says. It could be that cold tolerance comes at a cost to the lizard, he notes, so that in normal or warm winters, the cold-resistant lizards would be at a disadvantage. “I hope they will follow these populations over time to see if the cold tolerance stays at this new level,” Huey says.

Elizabeth Pennisi, “Cold snap makes lizards evolve in just a few months” at Science (August 3, 2017)

Why should we believe that this change is a form of evolution at all, as opposed to an existing capacity to adapt to unusual conditions that occur now and then? If the lizard is a common species, it probably has such capabilities.

So, mutations were not involved, Bob O'H? ET
This is OLD News! This phenomenon was discussed here at UD in the early part of 2008. I posted twice on the "rapid evolution" of the Italian wall lizard when transplanted from one Adriatic island to another, with 36/7 years intervening due to regional wars and such. When they went back to the island with the transplanted lizards, they found remarkable phenotypic differences, the major one being the development of 'cecal valves' in the stomach. Here's the kicker: the lizards were GENETICALLY IDENTICAL! There was no "evolution." There was simply phenotypic change, which we now understand quite well as 'epigenetic changes.' By the way, in the paper we're discussing, they DID NOT examine the genomes; rather, they examined the transcriptomes--that is, which genes were "turned on." They found that the transcriptome of the southern lizard had become identical to that of the northern lizard (which is adapted to the cold). So, two things: (1) This is not new stuff. We know how this happens--and it ain't "Evolution"! It's ADAPTATION! (2) genetic changes at the level of the genome were NOT investigated. Now, here are two posts from 2018: the first has to do with, you guessed it, "Rapid Evolution." And the second has to do with a discussion at Panda's Thumb about these lizards. In the second post, at comment 24, here is what I said to "jerry" (you'll notice that nothing has changed in 13 years--people have to die before ideas change!):
It’s an ‘epigenetic’ effect—Lamarkian in character; that is, I propose that the new food ingested by these lizards brought about the noted changes. A simple experiment would perhaps substantiate this: put some lizards in a sequestered area where the “plants” have been transplanted to the original island, and watch what happens in time. You would also have to put up some netting over the area to keep out the bugs that are their normal diet.
Now, I've posted about this before; but, it seems like it needs to be restated. They DID this experiment. And, so, in an article accepted in January 2010 and published in May 2010 in Physiological and Biochemical Zoology, reported these results:
Many comparative studies have tacitly assumed that the distinctive features of plant-eating lizards (large body size, skull dimensions, special dentition, gut morphology) are a product of genetic adaptation to the special demands of a plant-based diet (e.g., Van Damme 1999; Cooper and Vitt 2002; Espinoza et al. 2004; Herrel et al. 2008). Our results suggest that in P. sicula, at least some of the changes associated with a dietary shift toward a higher proportion of plant material may be plastic. Specimens from the Pod Mrc?aru population, which in nature eat substantial amounts of plant material (Herrel et al. 2008), exhibited a reduction in digestive tract length and a total loss of cecal valves after having been fed an exclusively arthropod diet for 15 wk. Although parts of their gastrointestinal systems were still better developed than those of specimens feeding mainly on arthropods in the wild, it seems likely that a prolonged exposure to an animal-based diet would have erased even those differences. These observations call for a more flexible view of the digestive system in lizards.
Remember, there were no genetic changes in these organisms. This is NOT evolution. Yet, it is touted as "rapid evolution." Thirteen years and the same mistaken Darwinian ideas are still around. Alas. PaV
Unfortunately, if I found the right article, it was **really** vague about the genetic component. Just "we found unspecified differences", not "we found differences that matter here". I believe the paper is this one, and the genetic component is Figure 4. johnnyb
ET - I think you commented on the wrong thread. Bob O'H
just another Darwinian misinterpretation of reality ... martin_r
So, mutations aren't random with respect to fitness. ET
Why should we believe that this change is a form of evolution at all, as opposed to an existing capacity to adapt to unusual conditions that occur now and then?
I'm sure some of it is, but they did also look at the DNA and found differentiation between the before and after populations. Bob O'H

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