So whatcha gonna do?Well, what creos need to do is obvious:
Posted on 06/08/2004 3:30:58 AM PDT by PatrickHenry
The first eyewitness to the birth of a new species may be a University of Arizona graduate student. Her new findings could help biologists identify and understand the precise genetic changes that lead one species to evolve into two separate species.
Laura K. Reed and her advisor Therese Markow, a UA Regents' Professor, made the discovery by observing breeding patterns of fruit flies that live on rotting cacti in western deserts. Whether the closely related fruit fly populations, designated Drosophila mojavensis and Drosophila arizonae, represent one species or two is still debated by biologists, testament to the UA researchers’ assertion that the insects are in the early stages of diverging into separate species.
The team's findings will be published the week of June 7 in the online early edition of the Proceedings of the National Academy of Sciences.
The seeds of speciation are sown when distinct factions of a species stop reproducing with one another. When the two groups can no longer interbreed, or just prefer not to, they stop exchanging genes and eventually go their own evolutionary ways, thus forming separate species.
While the evolutionary record is brimming with examples of speciation events, biologists haven’t been able to put their fingers on just what initiates the reproductive isolation, Reed said. Several researchers have identified mutant forms of certain genes associated with the inability of fruit flies to hybridize with closely related species. However, in all cases those genes were discovered long after the two species diverged. Therefore, those genetic changes could either have caused the speciation, resulted from it or even be incidental changes that happened long after the two species diverged.
Reed said the difficulty is researchers need to catch the genetic schism while it’s still brewing. Now she and her advisor have managed to do just that.
In the wild, the two fruit flies Drosophila mojavensis and Drosophila arizonae rarely, if ever, interbreed, even though their ranges overlap in a broad swath along the northern Mexican coastline. In the lab, researchers can coax successful conjugal visits between members of the two groups. But even under laboratory conditions such matings aren’t always fruitful. Drosophila mojavensis mothers typically produce healthy offspring after mating with Drosophila arizonae males, but when Drosophila arizonae females mate with Drosphila mojavensis males, the resulting sons are sterile. Reed said such limited capacity for interbreeding suggests the two groups of flies are on the verge of becoming completely separate species.
Another finding adds support to that notion. Previous research had shown that for a strain of Drosophila mojavensis from southern California's Catalina Island, mothers always produce sterile sons when mated with Drosophila arizonae males.
Because the hybrid male's sterility depends on the mother’s genetic heritage, Reed and Markow conclude the genetic change, or polymorphism, responsible for creating sterile sons must not be firmly established in Drosophila mojavensis populations -- a telltale sign that the change is recent.
Reed wanted to know just how deeply the polymorphism causing male sterility had suffused the Catalina Island Drosophila mojavensis populations. In other words, do just some of the Catalina Island mothers produce sterile sons when mated to Drosophila arizonae males? When Reed did the experiment, she found that only about half the crosses resulted in sterile sons. That result implies that only half the females in the Catalina Island population had the gene (or genes) that confer sterility in the hybrid male offspring.
Surprisingly, when she tested Drosophila mojavensis females from other geographic regions, Reed found that a small fraction of those populations also exhibited the hybrid male sterility polymorphism. “That polymorphism exists in every population I looked at,” Reed said. “It just happens to be that whatever factors are causing sterility are at higher frequencies in the Catalina Island population.”
Further experiments demonstrated that the sterility trait is caused by more than one genetic change. “I think there are many genes -- 4 or 5 probably, maybe many more,” Reed said.
Now that the researchers are hot on the trail of a set of “speciation genes,” the next task will be to identify them. For help in the hunt, the team will take advantage of the newly begun Drosophila mojavensis genome sequencing project, which will provide a complete roadmap of every gene in the species.
“Evolutionary biologists are excited to figure out what causes what we see out there—the relative forces of selection and drift -- whether things are adapting to their environment or variation is random," Reed said.
"Another important component to that is how that variation is partitioned into separate species. Once you’re a separate species, you have an independent evolutionary trajectory to some other species -- an independent set of tools, or genetic potential, relative to other species. So this partitioning of genomes is an important cause of the variation we see in nature.”
I can already anticipate the objections: "But they can't reproduce it in the lab!" Yes, but if something is done in the lab, the objection is that it can't be evidence of evolution because it's "designed." So whatcha gonna do?
Very intriguing! Wouldn't it be fascinating if speciation ultimately depends on a very limited number of particular genes? Perhaps it's just my perspective of things, but it seems to me that sympatric speciation has gained credence in recent years. I've always thought it was something worth examining in greater detail, because if geographical isolation is responsible for most (if not all) speciation, then why are so many very closely related species living in overlapping ranges?
This would give a milder boost to the concept of parallel speciation as well.
The clearest evidence for evolution are the creationists, for they have not evolved.
So let's see if I followed the argument. These two different kinds of flies mated which normally do not mate and produced a horse...no, a cactus...no, a snake...no, another fly. Imagine that! Evolution is something, eh?
The answer definitely appears to be: Nope. Sorry!
But, but, but, they're still the same KIND! /creo mode
Now you're just being mean.
I've been waiting for my yard to evolve into a lawn for years. My wife says I should play God an DO SOMETHING about it.................
So whatcha gonna do?Well, what creos need to do is obvious:
You can see she's got quite a mind.
This has nothing to do with evolution - there is no fossil record of the changes noted & you can't prove anything concerning evolution without a complete fossil record of the changes (including all the 'steps' involved). There also must be some higher 'intelligence' guiding the process and design otherwise it would never happen.
Inverse Limbo alert.
Thank you for your contribution to the thread.
Awesome! Was that cut and pasted?
Vade and PH, I was wondering if you ever saw the movie Top Secret? There is a scene in the beginning of the movie where an agent runs into a high-ranking villian's office with a report, stating that "such and such prisoners have escaped!!". The bad guy simlpy reaches into his desk and pulls out a nice sized stamp, which he then presses onto the paper. As he pulls the stamp away, the camera is over his shoulder, and you can see that the stamp says, in red, "Find them and kill them". It was a very funny scene, and it reminds me of some of these threads, when the creos show up with the same, pat responses to everything. What say you?
I like the part how, if you can't prove every step, none of it happened. A whole science of not seeing.
How can I reply to you? You have not left us a fossil record of your existence.
</creationism mode>
"Was that cut and pasted?"
No, it's an original rehash of ID arguments - straight from the shadows this am.
Reminds me of the gays. Someday there'll be a species called Homo Gaypiens.
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