Changing One Gene Launches New Fly Species

In what has been described as the "perfect experiment," evolutionary biologists at the University of Chicago replaced a single gene in fruit flies and discovered a mechanism by which two different "races" begin to become different species, with one group adapted to life in the tropics and the other suited to cooler climates. The tropical group was more tolerant of starvation but less tolerant of cold. The temperate group was less able to resist starvation but better adapted to cool weather.

The altered gene also changed the flies' pheromones, chemical signals that influence mating behavior. As a result, the researchers show in the Dec. 5 issue of Science, the two groups of flies are not only fit for different environments but may also be on their way to sexual isolation, a crucial divide in the emergence of a new species.

"This study directly connects genetics with evolution," said Chung-I Wu, Ph.D., professor and chairman of ecology and evolution at the University of Chicago and director of the study. For the first time, we were able to demonstrate the vast importance in an evolutionary context of a small genetic change that has already occurred in nature."

"We had the luxury," added co-author Tony Greenberg, Ph.D., a postdoctoral student in Wu's laboratory, "of watching the essential event in Darwinian evolution, the first step in the origin of a new species. We were quite impressed, that this simple alteration played such a dramatic role, both adapting flies to a new environment and changing their sex appeal. Once two groups become sexually isolated, there's no turning back."

The scientists used a new technique to knock out one gene from fruit flies and then replace it with one of two slightly different versions of the same gene.

They focused on a gene called desaturase2 that plays a role in fat metabolism. Flies from Africa and the Caribbean, where there is tremendous competition for food but cold temperatures are not a problem, have one version of ds2. Flies from cooler climates, where there is less competition for food but greater temperature variation, have a smaller, inactive version of ds2.

The same gene plays a role in the production of cuticular hydrocarbons -- waxy, aromatic compounds that coat the abdomen of female flies. A male fly, in a romantic mood, strokes the female's abdomen with his feet, which have sensors that recognize specific hydrocarbons, like a perfume.

In a previous report, Wu's laboratory found most males with the temperate version of the ds2 gene preferred females with the same gene; tropical males preferred tropical females.

"Developing increased cold tolerance was an important step for flies that migrated out of Africa to Europe and Asia," Wu said. The change in pheromones, which altered patterns of sexual attraction, "was a by-product of adaptation to colder weather."

Fruit flies have a migratory history similar to humans. They originated in Africa, spread to Europe and Asia and went on to populate the world. As with humans, there is greater diversity within African flies than between flies from Africa and other continents.

Although fruit flies have been a favorite model for the study of genetics since the early 20th century, recognition of consistent differences between tropical and temperate flies came only in 1995. The discovery, however, "has allowed a lot of analysis of the evolution of adaptive traits," Wu said.

"But this was the first time we have been able to study the process from the very beginning," he added, "to watch the first steps as one species begins to split into two, then seals the bargain by increasing sexual isolation. This is the essence of biodiversity."

Additional authors include Jennifer Moran from the Wu lab and Jerry Coyne of the University of Chicago. The National Institutes of Health and the National Science Foundation funded the study.

To reinforce your point.

The Fruit Fly in the Flight Simulator 12/08/2003
The simplest things can be the most extraordinary. If you like finding amazing wonders in everyday things, you’ll be fascinated to read about the common fly in the cover story of Caltech’s magazine E&S (Engineering and Science).¹ Michael Dickinson, a zoologist turned engineer, has described his Caltech team’s work trying to reverse-engineer the flight systems of the common fruit fly, Drosophila melanogaster.
Part of the fascination of this article is the team’s cleverness in experiments. Dickinson and his students have built elaborate flight simulators for the tiny insects. Imagine taking a fly, not much bigger than a large speck of dust, and putting it into a custom arena in which the scenery is computer controlled, and every response of the fly’s wings and muscles can be measured. Imagine fastening a tiny fly with a tether and monitoring its every movement. (This is reminiscent of the monarch butterfly flight simulator – see 07/09/2002 headline – only more elaborate.) Dickinson’s team measured the “swatting reflex,” to see how the fly changes its angle when a large unknown object approaches. They studied flight motion with high-speed cameras, and even built "RoboFly", a computer-controlled set of wings fed the exact motions of a real fly, to study the aerodynamic forces on the wings. Next, they are taking on the ambitious project of building a housefly-sized robotic insect that might be able to hover like the real thing.
All this pales in comparison, however, to the profuse praise Dickinson lavishes on the engineering capabilities of the real live insect. Listen to what he says, and you will take his concluding statement to heart, “I hope you will think before you swat.” Here are some samples from his 10-page, illustrated article (emphasis added):

CPU: Describing the fly’s ability to adjust flight processing in less than 30 milliseconds, “This is extraordinarily fast processing, and illustrates why the flight system of flies represents the gold standard for flying machines.” (p. 12)
Brain: “Insects have quite sophisticated visual systems, and approximately two-thirds of their brain (about 200,000 neurons) is dedicated specifically to processing visual information.”
Eyes: “Fruit fly’s eyes... have excellent temporal resolution and can resolve flashing lights at frequencies up to 10 times faster than our own eyes can. This means if you take a fly on a date to the movies it will think you brought it to a slide show.”
Systems-level analysis of fly mechanics: “Here things get rather humbling, because it’s the mechanical component of this biological system that we, as engineers, are the furthest away from being able to replicate.”
Materials science: “Flies don’t have an internal skeleton consisting of individual bones or cartilage. Instead, they’re surrounded by an external skeleton, the cuticle—a single, topologically continuous sheet composed of proteins, lipids, and the polysaccharide chitin. During development, complex interactions of genes and signalling molecules spatially regulate the composition, density, and orientation of protein and chitin molecules. Temporal regulation of protein synthesis and deposition allows the construction of elaborate, layered cuticles with the toughness of composite materials. The result of such precise spatial and temporal regulation is a complex, continuous exoskeleton separated into functional zones.; for instance, limbs consist of tough, rigid tubes of ‘molecular plywood’ connected by complex joints made of hard junctures separated by rubbery membranes.”
Joints and Hinges: “Perhaps the most elaborate example of an arthropod joint, indeed one of the most complex skeletal structures known, is the wing hinge of insects–the morphological centerpiece of flight behavior.” (He describes how the parts function.) “Although the material properties of the elements within the hinge are indeed remarkable (resilin is one of the most resilient substances known), it is as much the structural complexity as the material properties that endows the origami-like wing hinge with its astonishing properties.”
Flight mechanics: “By controlling the mechanics of the wing hinge, the steering muscles act as a tiny transmission system that can make the wing beat differently from one stroke to the next. Electrophysiological studies indicate this is a phase-control system.” He describes how the steering muscles can actually alter the stiffness of the wing in flight. “The fly uses the steering muscles as phase-control springs to alter the way the large strains produced by the power muscles are transformed into wing motion.”
Timing: “During each wingbeat, sensory cells on the wings and halteres send timing signals into the brain that are used to tune the firing of the muscles.” Considering the speed at which their wings beat, this is certainly a rapid-response system.
Gyroscopes: “The information coming from the haltere,” (a drumstick-shaped organ behind each wing) “is particularly important because it is essential in stabilizing reflexes. Beating antiphase to the wings, the halteres function as gyroscopes during flight.” (He describes how these organs respond to Coriolis forces with appropriate compensatory reflexes.) “The animal detects these rotations with its halteres and responds with compensatory changes in wing stroke. These reflexes are extraordinarily robust.... The halteres are essential elements of the fly’s control system. Cut them off, and a fly rapidly corkscrews to the ground.”
Computation: “Because of the complexity of fly aerodynamics, understanding wing motion does not necessarily translate into an understanding of flight forces. It is a common myth that an engineer once proved a bumblebee couldn’t fly, and while the true story is really much kinder to the engineer, it underscores the difficulties of studying fly aerodynamics. At present, even brute-force mathematical computations on supercomputers cannot accurately predict the forces created by a flapping wing.”
Wow. All this in a tiny fly! Wrapping up this amazing journey into miniaturized ultrasophisticated engineering, Dickinson puts his work into perspective:
In the end, it’s just a fly. Is such an insignificant organism really worth all this effort? The natural world is filled with complex things, like immune cells, the human brain, and ecosystems. Although we’re made great progress in deconstructing life into its constituent parts such as genes and proteins, we have a ways to go before we have a deeper understanding of how elemental components function collectively to create rich behavior. The integrative approach that we are using to study fly flight is an attempt to move beyond reductionism and gain a formal understanding of the workings of a complex entity. The fly seems a reasonable place to start, and if successful, I hope such work will stimulate similar attempts throughout biology. The lessons learned along the way may provide useful insight for engineers and biologists alike. Even if you don’t buy such grand visions, I hope you will at least think before you swat.

¹Michael H. Dickinson, “Come Fly With Me,” Engineering and Science, Volume LXVI, No. 3, 2003 (Caltech), pp. 10-19.
Thank you, Dr. Dickinson, for a wonderful glimpse into one of nature’s miniature engineering marvels. We feel like we were sitting behind you on the fly’s back, soaring on a thrill ride, like your first picture humorously illustrates. Thank you, also for reminding us that the world is filled with wonders like this, from bacteria to blue whales. Wow. Who would have suspected such wonders exist in a tiny fly? Certainly not Charles Darwin. Which reminds us, we were about to award you Story of the Month for this outstanding scientific article, but you included this one statement which acts like the proverbial fly in the ointment: “The information coming from the haltere, a hindwing modified by evolution and resembling a very small chicken drumstick, is particularly important because it is essential in stabilizing reflexes.” We regret, therefore, to have to award you, instead, Stupid Evolution Quote of the Week.

Link

Updated list of responses from the denial crowd. I had predicted the first 7, the rest come from comments. My last listing (post 70) listed 20. Those that follow number 20 come after post 70:

It's a designed experiment. That proves ID!

It's a lie!

It hasn't speciated yet!

Blasphemy!

They're interpreting it through their naturalistic materialistic worldview.

How dare you use the screen name "PatrickHenry"?

Yeah, but "get your own dirt!"

This is only micro evolution, not macro evolution

They said: "... may also be on their way to sexual isolation ..." so it's typical evo weasel wording!

Playing god is what they are doing.

The point is this was done MANUALLY, It was NOT observed naturally ...

... we as a people aren't all that bright. How much tweaking does it to take to do serious damage.

A deliberate laboratory forced change does NOT equal natural change.

Speciation my butt.

Now I admit, this is interesting even exciting, but proof? speciation?

So desperarate for REAL evidence of speciation, they will unashamedly boast of this?

Gee, a fly got turned into. . . a fly! Imagine that!

Does the article say if the differentiating species can still interbreed?

But will the "new species" be able to procreate?

[Y]ou aren't nearly as intelligent as your reply here indicates you believe yourself to be.

PatrickHenry, unable to intellectually respond to any of the responses, is forced to merely list them.

So did God or mutation change the gene or was the change a product of intelligent design by some lab maven?

If evolution is based on chance mutation, the odds of several fruit flys altering in the same way, that one gene, are slim.

Did God do it, Patrick, or some scientist? Darwinism is in the eye of the beholder, Patrick.

Good stuff. Keep 'em coming!

Isn't odd how the ostensiably "conservative" creationists continually exaptiate the Left's relativist and anti-naturalist arguments for themselves.

Not odd at all. The "denial syndrome" is exceedingly common on the left. I'm not saying that creationists are leftists. Most of them around here aren't, and would pass out at the suggestion. But deep down, waaaaay deep, there is a psychological similarity.

Consider how leftists during the 20th century had to deny the terror of Stalin, deny the fact that the American communist party was a tool of Moscow, deny that Hiss was a commie, etc. All some weird, sick, very elaborate kind of mental mechanism to deny reality and thus maintain an insane ideology. How much can one deny in order to cling to a fantasy version of the world? There seems to be no limit.

If you have the "denial-type mentality" are there other reality-denying ideological worldviews in which you can find a home? Sure. Lots of them. And being attracted to one doesn't imply any sympathy for the "content" of the others. They're all "intellectually" unrelated. But they all have reality-denying true believers at their core: holocaust denial, moon-landing denial, Afro-centricism (that is, history-denial), and as you noticed, leftists (whose politics and economics are demonstrably insane).

The great virtue of science is that it faces the data without bias, and is unafraid to abandon an hypothesis that is demonstrably false. This "reality-based" outlook is the source of the success of the scientific worldview. Any other "reality-based" systems? I can think of a few: capitalism, the US Constitution (as originally written), and virtually all of English common law.

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