[meteorite-list] Fossil Plant and Insect Communities Key to Understanding Global Change and Mass Extinctions

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:18:30 2004
Message-ID: <200302251741.JAA00609_at_zagami.jpl.nasa.gov>

http://www.psu.edu/ur/2003/leafinsects.html

Fossil Plant and Insect Communities Key to Understanding Global Change
Pennsylvania State University
February 16, 2003

Denver - Insect damage recorded in fossil plants and the types of plants
present in the fossil record are helping researchers to understand how
ecological communities recover from climate change and mass extinction
events, according to a Penn State paleontologist and his colleagues.

Researchers looking at plant communities and insect predation on leaves at
both the Cretaceous-Tertiary boundary 65.51 million years ago and 10 million
years later at the Paleocene-Eocene boundary, can track the changes in
plants and insects through time. The K-T event, which marked the extinction
of the dinosaurs and more than 50 percent of all plant species, was caused
by the impact of an extraterrestrial object, while the P-E interval was a
more gradual change from one climate regime to another caused by a long-term
global warming trend.

"The early Eocene 52 million years ago was the warmest the Earth has been in
the last 100 million years, and that warming lasted for 2 million years,"
says Dr. Peter Wilf, assistant professor of geosciences at Penn State.
"There is strong evidence for high diversity when temperatures were warm,"
Wilf told attendees at the annual meeting of the American Association for
the Advancement of Science Feb. 16 in Denver.

Plants respond to climate change by migrating, evolving and going extinct.
However, Wilf notes that due to human activity, global change is occurring
at breakneck speed today. Because of the geologically rapid pace of
human-induced extinctions, habitat loss and climate changes, land plants
currently face a situation more closely resembling the K-T than the P-E
boundary.

Both the plant and insect studies used three fossil areas for samples; the
K-T was represented by fossil beds in North Dakota, while the P-E was
represented by two areas in Wyoming. Reporting on the fossil plant
communities were Wilf; Kirk R. Johnson, curator of paleontology, Denver
Museum of Nature & Science; and Scott L. Wing, National Museum of Natural
History, the Smithsonian Institution. In a subsequent paper, Wilf, Johnson
and Conrad C. Labandeira, National Museum of Natural History, the
Smithsonian Institution, discussed the role of insects in teasing out
climate change influences on ecological communities.

Fossilized leaves show a record of insect predation not unlike what is seen
on leaves today. On some leaves, the imprint of piercing and sucking insects
is visible. Others show the ragged margins or holey centers of leaves chewed
by hole feeding and margin feeding insects. Evidence of mining insects is
also preserved, as are galls. The fossil record preserves even the totally
skeletonized leaves that show only veins.

By looking at the damage, the researchers can categorize the types of
insects that infested these forests 65 and 55 million years ago, and trace
the extinction and evolution of species. Labandeira looked at 13.5 thousand
leaves across the K-T and identified 51 types of insect feeding damage. The
researchers found that the K-T impact was associated with a significant and
enduring loss of plant and insect species. Among insects, the most affected
were the specialized feeders, those insects that fed on leaves of only one
type of plant.

Insects died both from the impact and because the trees that they fed on
died. Specialized feeders were less able to adapt and eat off any tree
available and so were more greatly effected.

"At the K-T boundary, we see the largest spike of the last appearance of
species, both for plants and insects that ate them," says Wilf. "Although
climate change was occurring for a long time before the K-T, its effects
could not hold a candle to the extinctions brought on by the impact."

Only 21 percent of species made it across the K-T boundary and only 11
species originate in the Paleocene indicating the recovery was not
immediate. In fact, diverse vegetation does not return in the area studied
until the warm early Eocene 12 million years after the impact.

"The P-E transition was a relatively long, slow change that allowed the
plants and insects to adapt to the shifting environment," says Wilf. "At the
K-T, species could not adapt in time because the change was so rapid. These
rapid changes were much more like what we have today than the gradual ones
that occurred at the P-E. Organisms cannot migrate in response to climate
changes as they did during the Eocene because of because of freeways and
parking lots, and the ongoing loss of habitat imposes severe and
geologically sudden stress on ecosystems."

                                   **aem**

EDITORS: Dr. Wilf is at 814-865-6721 or at pwilf_at_geosc.psu.edu by e-mail.
Dr. Johnson is at 303-370-6448 or at Kjohnson_at_dmns.org by e-mail. Dr. Wing
is at 202-357-2649 or at wing.scott_at_nmnh.si.edu by e-mail. Dr. Labandeira is
at 202-357-2971 or labandeira.conrad_at_nmnh.si.edu by e-mail.

Contacts:
A'ndrea Elyse Messer (814) 865-9481 aem1_at_psu.edu
Vicki Fong (814) 865-9481 vfong_at_psu.edu
Received on Tue 25 Feb 2003 12:41:55 PM PST