For what it’s worth:
Often compared to Darwin’s finches, the stickleback species pairs provide a powerful and tractable comparative model to test natural selection’s role in the speciation process. Although benthic and limnetic sticklebacks usually refuse to mate with each other, two benthics or two limnetics from different lakes that evolved in complete isolation for thousands of years will happily interbreed. “Repeatedly we see the same mechanism of reproductive isolation evolve in lock step with adaptation to their environment,” says UBC evolutionary biologist Dolph Schluter. “Natural selection is the only process that can do that.”
Scientists fear, however, that this so-called “natural laboratory system” doesn’t have enough replicates, especially as two of the five known species pairs have already been effectively wiped out by introduced species. Gow’s discovery - the first in more than two decades - is good news for conserving the critically endangered sticklebacks. But it’s also a boon for biological research.
Soon after bringing the fish back to her UBC lab, Gow walked down the hallway to Schluter’s office, Little Quarry Lake sticklebacks in hand. When Schluter saw the fish, he was immediately taken aback. “Oh my god, they sure looked like limnetics and benthics,” he recalls. Using genetic markers and morphological features, Gow and Schluter showed that the Little Quarry Lake sticklebacks were, indeed, a true species pair (Can J Zool, 86:564-71, 2008).
Gow and Schluter also found a fairly unique characteristic in the Little Quarry Lake benthic species: The fish lacked a pelvic girdle, the bony modified pelvic fin that is the equivalent of tetrapod hind limbs in most sticklebacks. Schluter had found this only once before in the five other British Columbia species pairs.
In 2004, together with geneticist David Kingsley at Stanford University, Schluter showed that regulatory changes in the Pitx1 gene led to pelvic girdle loss in both the benthics from Paxton Lake on Texada Island, BC, and in another population of nonpaired sticklebacks from Iceland (Nature, 428:717-23, 2004). Could the same mutation be at work in the Little Quarry Lake fish?
Kingsley and Schluter have already teased apart the genetic basis of another post-glacial stickleback feature: the loss of numerous protective armor plates. In 2005, they showed that a single mutation lurking at low frequencies in the marine ancestor was responsible for the parallel evolution of armor plate reductions in dozens of freshwater stickleback populations around the world (Science, 307:1928-33, 2005).
But armor plate changes are as “common as cockroaches,” says Kingsley. Since pelvic reductions are much rarer, they probably don’t stem from ancient, preexisting mutations, or we would see fewer freshwater girdles by now, he adds. Rather, each mutation causing pelvic reductions probably arose anew, including in the Little Quarry Lake benthic species. “That makes every single population of great interest,” says Kingsley.
Excerpt. Read more at: http://www.the-scientist.com/article/display/55360/
“For what it’s worth:”
No much: here’s why.
“a powerful and tractable comparative model to test natural selection’s role in the speciation process”
opening with a conclusion. not promising; classic manipulative technique. let’s see if it’s true.
“two benthics or two limnetics from different lakes that evolved in complete isolation for thousands of years”
LOL!! “evolved in complete isolation for thousands of years”. How do they know this? Did the stickleback tell them? I though evolution took millions of years, not mere thousands! that whole premise smells bad.
“Repeatedly we see the same mechanism of reproductive isolation evolve in lock step with adaptation to their environment”
what a load of tardedness. “mechanism of reproductive isolation” = they won’t mate, mate.
“Natural selection is the only process that can do that.”
ooh. another conclusion with nothing to back it up. I’m soooo impressed.
(blah filler)
“equivalent of tetrapod hind limbs in most sticklebacks. Schluter had found this only once before in the five other British Columbia species pairs.”
only once before!!?? wow.
“Could the same mutation be at work in the Little Quarry Lake fish?”
could you have ANY less to write about?
“post-glacial stickleback feature”
hey look, it’s a premise. everyone wave to the nice premise.
“they probably don’t stem from ancient, preexisting mutations”
oh I just looove “probably” articles, don’t you?
so, with a bunch of sciencey, high-sounding words to make you think they know what they are talking about, what they are basically saying is, there was a mutation, they don’t know why, they don’t know what, they don’t know where. but the have LOADS of premises and assumptions and conclusions and religious worldviews they’d just love to shove down your throat on the basis of it though.