Sunday, September 24, 2006
Evolutionary Warfare
There is an interesting evolutionary struggle going on in Hawaii that has nothing to do with creationists trying to undo the Enlightenment. Somewhere in Hawaii, a population of crickets has grown eerily silent. The culprit? Evolution. To avoid detection by a parasitic fly, the insects have--over only 20 generations--developed wings that don't chirp. But the silence has its downside: The muted males can no longer catch the attention of potential mates.
Two interlopers to the islands are duking it out in ways that may spell both their dooms. The black field cricket (Teleogryllus oceanicus), originally from Fiji, Tahiti, and Australia has now become the prey of a parasitic fly (Ormia ochracea), which is native to North America. A population of black field crickets on the island of Kauai that is being studied by behavioral ecologist Marlene Zuk of the University of California, Riverside, has up to a third of its individuals infected by the fly, which were homing in on the male's mating chirps.
Zuk noted a decrease, over a number of years, in the mating calls of the cricket and assumed it indicated a decrease in the population. However, starting in 2003, she noticed an actual increase in the population but without a concomitant increase in the mating calls. It turned out that, in the incredibly short period of about 20 generations, or 4 or 5 years, large numbers of the crickets had developed wings that lacked the grooved ridges that, when the wings are rubbed together, causes the characteristic mating chirp.
But then, how do the chirpless crickets find mates?
When researchers played recorded mating calls in the center of a patch of grass, 108 silent crickets came to within 125 centimeters of the speaker--up to three imes the number of crickets that gathered in similar experiments on the big island of Hawaii and on Oahu, where the parasitic flies attack a lower percentage of crickets. That suggests that flatwing males position themselves close to normal males from their local population and intercept females attracted to the call of the normal males ...
Since the flies have now become dependent on the crickets, this evolutionary arms race could result in mutual assured destruction.
Still, whether this struggle for survival will allow the flies and crickets to coexist peacefully or end in mutual annihilation is anyone's guess. The flies have grown to depend on the crickets, but the male crickets are having a harder and harder time finding a mate. Evolutionary biologist Darryl Gwynne of the University of Toronto at Mississauga says he's waiting "with bated breath to see what evolution is going to give us."
Oh, wait a minute . . . evolution doesn't happen. Bronze Age shepherds told me so.
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I think the creationists will put their fingers in their ears and chirp real loud. ;-)
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: 10:20 PM
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