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.