From: LARRY KLAES (ljk4_at_msn.com)
Date: Mon May 05 2003 - 17:25:38 PDT
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From: cunews_at_cornell.edu
Sent: Monday, May 05, 2003 6:32 PM
To: CUNEWS-AG-L_at_cornell.edu; CUNEWS-LIFE_SCIENCE-L_at_cornell.edu; CUNEWS-SCIENCE-L_at_cornell.edu
Subject: Cornell News: Army ants defy evolution
Army ants, as voracious as ever, have defied evolution for 100
million years, Cornell entomologist finds
EMBARGOED UNTIL MONDAY, MAY 5, 2003, AT 5 P.M. EDT
Contact: Blaine P. Friedlander Jr.
Office: 607-255-3290
E-mail: bpf2_at_cornell.edu
ITHACA, N.Y. -- Army ants, nature's ultimate coalition task force,
strike their prey en masse in a blind, voracious column and pay no
attention to the conventional wisdom of evolutionary biologists.
The common scientific belief has been that army ants originated
separately on several continents over millions of years. Now it is
found there was no evolution. Using fossil data and the tools of a
genetics detective, a Cornell University entomologist has discovered
that these ants come from the same point of origin, because since the
reign of the dinosaurs, about 100 million years ago, army ants in
essence have not changed a bit.
"Biologists have wondered why army ants, whose queens can't fly or
get caught up by the wind, are yet so similar around the world. Army
ants have evolved only once and that was in the mid-Cretaceous
period," says Sean Brady, a Cornell postdoctoral researcher in
entomology, whose study was conducted while he was doctoral candidate
at the University of California-Davis.
Brady's paper, "Evolution of army ant syndrome: the unique origin and
long-term evolutionary stasis of a novel complex of behavioral and
reproductive adaptation," will be published on the Web by the
Proceedings of the National Academy of Science (PNAS) Online Early
Edition between May 5 and May 9 before being printed in PNAS.
Army ants are quite unlike the ants commonly found at family picnics.
They have what scientists call the "army ant syndrome," comprising
three characteristics: the ants are nomadic, they forage for prey
without advance scouting, and their wingless queens can produce up to
4 million eggs in a month. While this syndrome is found in every
army ant species around the world, scientific papers have postulated
that army ants evolved these characteristics multiple times after the
breakup of the supercontinent Gondwana about 100 million years ago.
In total, Brady studied the DNA of 30 army ant species and 20
possible ancestors within the army ant community, divided between the
New World species in Ecitoninae and the Old World groups Aenictinae
and Dorylinae. He specifically sought information from four different
genes to uncover clues to their relationships. "Essentially I built
a genetic family tree. Then I took that family tree and looked at its
genetic tree rings to postulate what happened in the past," he said.
Brady combined the genetic data with the army ant fossil information
and the ants' morphological (form and structure) information to
establish ages for the different ant species. Combining this data,
Brady found that all the species share some of the same genetic
mutations. "If they share those mutations, we can infer they evolved
from the same source," Brady said.
Instead of proving the common assumption that the Old World and the
New World army ants developed their lineage independently on separate
continents, the entomologist showed the ants evolved only once -- on
Gondwana.
Brady examined the army ants' behavior on his trips to the Amazon
jungle, Brazil's savanna region and the country's coastal rain forest
near São Paulo. Periodically millions of army ants would march
together through his camp, he says, like a flowing river of red.
While the ants move silently, their presence is announced. "The other
insects are scared, and they make noises as they flee the invading
army," Brady says. "Ant birds follow the ants from the sky and feast
on the remnants left behind by the ants. You will hear the
high-pitched chirping of the other insects, and you'll hear them and
other small animals scurrying in fear. They know what is next."
Related World Wide Web sites: The following sites provide
additional information on this news release. Some might not be part
of the Cornell University community, and Cornell has no control over
their content or availability.
o PNAS Online Early Edition: <http://www.pnas.org/papbyrecent.shtml>
-30-
The web version of this release may be found at
http://www.news.cornell.edu/releases/May03/ArmyAntBrady.bpf.html
Cornell University News Service
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Cornell University
Ithaca, NY 14853
607-255-4206
cunews_at_cornell.edu
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