Posted on 03/20/2006 2:12:01 PM PST by restornu
Wings could be a passing phase for the giant prickly stick insect
The big wing switchThe lowly stick insect has forced a rethink of one of the key rules of evolution - that complex anatomical features do not disappear and reappear over the course of time.
Researchers have discovered that on a number of occasions in the past 300 million years, stick insects have lost their wings, then re-evolved them. Entomologists have described the revelation as "revolutionary".
Michael Whiting, an evolutionary biologist from Brigham Young University in Provo, Utah, and his team stumbled upon the finding while examining the DNA of 37 different phasmids, the stick and leaf insects famous for camouflaging themselves against plants, in a bid to work out their family tree.
Entomologists have assumed that wings only evolved once in insects. The received wisdom is that a winged ancestor produced the winged phasmids we see today. The 60 per cent of stick insects that do not sport wings will, this thinking goes, have jettisoned them along their evolutionary journey so they could expend more energy on reproduction and less on flying.
But Whiting's analysis shows that the very first stick insect, which appeared 300 million years ago, had already lost its wings and that stick insects re-evolved the structures at least four times (see graphic). The study covers only 14 of the 19 known sub-families of phasmids, so it is possible that wings reappeared even more often.
Beyond repair Researchers assumed wings could not come back once lost as the genes needed to create them would mutate beyond repair once the wings disappeared. But Whiting says there is evidence from the fruit fly Drosophila that the same genes contain instructions for forming wings and legs.
If the same were true for stick insects, there would be an evolutionary pressure to stop wing genes from mutating, even in the insects that did not have wings. Those genes could then be turned back on in the future.
Whiting says, however, that while wing re-evolution may seem unlikely to insect researchers, the basic idea of switching regulatory genes off and on is well accepted. Even a single gene can sometimes switch on the growth of a complex structure - studies indicate that a master gene called Pax-6, for example, might control the development of eyes in all creatures that have them.
So Whiting suggests that eyes too could have disappeared and reappeared in animals over time. "I remember sitting down with entomologists and hearing them say 'impossible, impossible, impossible'," he says. But "re-evolution is probably more common than we thought".
Journal reference: Nature (vol 421, p 264)
Today I was reading an article where the writer was referring quite comfortably to "insertions, deletions, and mutations" as the source of new or different genes.
That's pretty new stuff ~ 10 years ago they'd have accused you of dipping too much snuff if you included "deletions" or "insertions" with "mutations".
So, stick insects turn their wings on and off ~ through time ~ so much for "...... key rules......".
Somebody is making up rules on the fly.
Somebody is making up rules on the fly.
Turns out that the vast majority of our DNA is not active - like files on a computer whose pointers have dissappeared. Occasional "archaic DNA" gets expressed once in a great as a vestigial tail or a penis bone.
Evolution only favors adaptive traits.. not complexity over simplicity.. otherwise whales wouldn't have evolved away their limbs..
Genetic traits may submerge for a time, but then re-emerge, indicating that the trait was probably never lost in the first place.
ping
Another factor is while living things existing today had ancestors, not all fossils had descendants. Or we can't be sure that the fossils without wings were the ancestors of the later fossils with wings. There may always have been a few insects with wings around. Very few living things actually end up fossilized.
Really. No one ever told me about that rule. No one ever disputed that ancestral whales first lost and then gained fins.
But they could without getting permission from science. Evolution implies progression, but going around and around a course is also progression. Check with NASCAR.
Nothing wrong with penis bones.
The business of turning genes on, and turning genes off is "new".
That is what the word means. Maybe it is unfortunate they chose that word to symbolize what they were signifying, but it is much older than Darwinism. Old traits do come back sometimes, even in pea plants.
Huh, how could the very first one have already lost its wings???
Now if they'd kept their lungs, we'd have giant insects walking about, eating stuff, talking, doing everything you can do without bones. Unfortunately, for the bugs, the alternative breathing mechanism simply isn't all that good in today's thin atmosphere.
Given that we are talking about "lung genes", it's possible the stick insects have been acquiring "insertions" from an unanticipated source.
Source: Alan Templeton's Laboratory Source: Washington University Department of Biology in Arts & Sciences
[St. Louis, Mo., February, 2003] - (This study appeared in Nature on Jan. 16, 2003) An evolutionary genetics graduate student at Washington University in St. Louis is part of a research team that shows a certain group of insects illustrate a spin of an ancient adage: if at first you don't succeed, fly, fly again.
Taylor Maxwell, Washington University graduate student studying under Alan R. Templeton, Ph.D., professor of biology at Washington University, helped analyze DNA sequences of many of 35 species of walking sticks, aptly named insects that mimic twigs to stay hidden from predators, to decipher which evolved first. Maxwell and his collaborators at Brigham Young University discovered that some species lost the ability to fly at one point of their evolution and then re-evolved it 50 million years later. Moreover, the data indicate it is likely that re-evolution of these species may have occurred more than once.
Such a conclusion means that the theory of evolution itself must continue to change.
"For entomologists, acquiring wings and the ability to fly was only thought to have occurred once in insect evolution," said Maxwell, who performed the bulk of the DNA sequencing for the study courtesy of National Science Foundation funding as an undergraduate at Brigham Young University. " Our results infer at least one, if not more, reoccurrences of flight after it had been lost.
"For evolutionary biology, this represents multiple gains of a complex character, presumably controlled by many genes and developmental processes. For developmental biologists and those studying insect flight, we have now presented them with a set of study organisms that may lead them to a greater understanding of evolutionary developmental processes and the molecular mechanics of flight."
Integrative biology professor Michael F. Whiting, Ph.D., of Brigham Young University, led the research team. Their findings, reported in the cover article in the Jan. 16, 2003, edition of "Nature," showed that some species of walking sticks without wings existed before their winged descendants, the first time any organism has been shown to do what scientists previously thought impossible -- re-evolve a complex trait.
"For complex functions like flight or sight, the idea in evolution has always been that organisms either use it or lose it," said Whiting, referring to Dollop's Law, which, as cited in the "Encyclopedia of Evolution" is "the principle that organs or complex structures cannot return to a condition seen in an ancestor."
"This is the first example of a complex feature being lost and recovered much later in an evolutionary lineage" Whiting said. "Even though the wing is not physically there, the underlying genetics which construct wings appear to be conserved over evolutionary time. It suggests that complexity can be maintained over tens of millions of years."
Entomologists have frequently documented cases where species of insects have lost the ability to fly. For example, many insect species that migrate to islands eventually lose wings as an adaptation to keep them from blowing into the sea. Bugs that live on snow don't have wings, and therefore have less surface area and lose less heat.
Whiting reasons that walking sticks lost wings because doing so helped them blend in with their surroundings. He also noted that wingless insects have been shown to lay more eggs than winged relatives, which could have been important for walking sticks, which often drop eggs to the earth from their treetop homes instead of burying them in the ground like similar insects do. Creating more eggs gives the wingless walking sticks a greater potential to pass their genes to the next generation.
"At least 50 million years later, for some reason, it was to their advantage to have some of the species become winged again," Whiting said, noting that various species of winged and wingless walking sticks now exist. "The remarkable thing was that they had the ability to generate wings when they needed them."
Whiting believes the instructions for growing wings are related to the instructions for making legs and can be turned on and off over long periods of time. The new study means evolutionary lineages can be more adaptive than previously thought, with the ability to move back and forth from a winged or wingless state. He expects future studies to show similar results in cockroaches and other insects, and possibly even in other classes of animals.
The walking stick project began when Whiting, an entomologist with a $1.34 million grant from NSF to construct the family tree of the insect class, asked Taylor Maxwell, then a Brigham Young undergraduate, to sequence and analyze the DNA of several species of walking sticks as part of the broader study. Maxwell, supported by grants from the Brigham Young University administration and the NSF designed to facilitate undergraduates' participation in research, put together preliminary results.
"As a pre-med major, I was barely learning that there were these fields of research out there," said Maxwell, a study co-author. "Dr. Whiting is very good at introducing people to science and very good at training people in the lab. Fortunately, the results we came up with were very strong with well-supported data."
After Maxwell's initial effort, Whiting embarked on a global scavenger hunt, seeking key species of walking sticks thought by experts to be the most primitive, which would help flesh out the study. He brought back samples from Australia, New Guinea and Chile with the aid of Sven Bradler, a graduate student at George August Universitat in Gottingen, Germany, and the study's other co-author.
Maxwell is now applying the concepts and techniques he learned in Whiting's lab to his current research into genetic issues related to cancer drugs as an NSF Predoctoral Fellow in a doctoral program at Washington University, a position he believes he earned in large part because of his undergraduate research experience.
"When I started this project, I just wanted to get some research experience that would help me get into graduate school," Maxwell said. "I never thought I would end up co-authoring a paper in Nature."
" received wisdom "
Is that sorta like the Textus Receptus?
Nutty as a fruitcake, Naw... It's a natural point to be debated, since "Evolution" IS somewhat of a misnomer for Natural Selection. But I believe he Jones is just plain wrong if he believes this undermines modern Natural-Selection/Genetic-Morphology holdings:
My understanding is that the failure of a single DNA pair can cause insects to exhibit fantastic changes in a single generation. If Wingless insects have experienced wings blinking in and out of existence, it actually means Natural Selection is actually EASIER to occur than traditional Evolutionists imagine. Consider that Darwin's Evolution of the Species predated Mendel's genetic work, let alone Watson and Crick demonstrating how it occured. These findings are entirely consistent with Mendellian genetics and Watson and Crick's, I suspect.
What he is referring to with Drosophila: While legs and wings take many, many genes to code for; there are certain "switching genes" which code for their placement and activation, and the two anatomical structures share a common morphology, like vertibrate fins, wings, legs and arms. Scientists have been able to mutate a single gene pair to cause legs to grow where wings or antennae would grow naturally.
I'm not sure how well Nicola Jones is distorting Whiting's article, but even as described, Whiting seems plausible.
>> Somebody is making up rules on the fly. <<
Is that a deliberate pun? If that is so, it's very, very funny, since these rules were made up on the Drosophila fly!
What, are you following me :^)?
>> Nothing wrong with penis bones. <<
I don't know about that. They say you should consult a doctor if an erection last for longer than four hours.
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