[meteorite-list] When The Asteroid Hit, Most Plant-Eating Bugs Died

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:54:10 2004
Message-ID: <200202250006.QAA18268_at_zagami.jpl.nasa.gov>

http://www.rockymountainnews.com/drmn/home/article/0,1299,DRMN_1_998663,00.html

When the asteroid hit, most plant-eating bugs died
By JIM ERICKSON
Rocky Mountain News
February 22, 2002

When a 6-mile-wide asteroid slammed into Earth 65 million years ago, it
wiped out the dinosaurs, about 80 percent of the world's plant species, and
all animals bigger than a cat.

But what happened to the bugs?

It's been tough for scientists to determine how the insects fared because
they rarely leave behind fossils.

But a Denver paleontologist and his Smithsonian Institution colleagues found
a way around the problem: By studying insect damage etched into thousands of
fossil leaves, they determined that many plant-eating bugs perished in the
big impact.

"These little insects are leaving their calling cards on the fossil leaves,
and we have an excellent fossil record of leaves," said Kirk Johnson,
curator of paleontology at the Denver Museum of Nature & Science.

"So by looking at the insect damage on the leaves before and after the
dinosaur extinctions, we can make a pretty good educated guess of what
happened to the insects."

Johnson and his collaborators estimate that 55 percent to 60 percent of
plant-eating insects were exterminated. Their findings are reported in this
week's Proceedings of the National Academy of Sciences.

Over the past 20 years, Johnson has collected 13,441 plant fossils from
quarries in southwestern North Dakota.

When the asteroid hit Mexico's Yucatan Peninsula, it threw up clouds of dust
that traveled around the globe. Johnson pulled fossils from rock layers
directly above and below those sediments.

At the time, southwestern North Dakota was a warm, forested plain with lots
of broad-leafed trees.

Some leaves, now stored at the Denver museum and at Yale University, are up
to a foot long. Individual leaf veins are visible, as are the diagnostic
chomp marks, tunnels and holes left by prehistoric beetles, grasshoppers,
butterflies and moths.

Certain insects rely on a single species of plant for sustenance; others are
generalists that feed on several plant types.

By analyzing insect-damaged leaves before and after impact, researchers
determined that the generalists survived, while 70 percent of specialists
did not.

Smithsonian entomologist Conrad Labandeira was the lead author of the
research paper. The third author is Peter Wilf of the Smithsonian and the
University of Michigan.
Received on Sun 24 Feb 2002 07:06:49 PM PST