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May 12, 2005
Contact: Roger Martin, KU Center for Research, (785) 864-7239.

KU researcher helps discover earliest known lichen fossils in South China


LAWRENCE -- Evidence suggests that lichens existed on Earth 200 million years earlier than previously believed, according to researchers from China and the United States.

Ten years ago, Thomas N. Taylor, a University of Kansas researcher, and German colleagues reported in Nature that the earliest fossil evidence of lichens on Earth, from Scotland, dated to about 400 million years ago.

But in the May 13 of Science, Taylor, along with researchers from the Nanjing Institute of Geology and Paleontology and Virginia Tech University, report fossil discoveries from South China that push the date back millions of years.

The scientists agree that the discovery raises questions about the evolutionary relationship between the very old and the very, very, very old lichens.

Members of the team were Taylor, KU professor of ecology and evolutionary biology; Chinese paleontologist Xunlai Yuan; and Virginia Tech assistant professor of geosciences Sunhai Xiao.
In the Science article, the team reports having discovered three lichen specimens, preserved in a mineral called phosphorite, dating from between 551 million years and 635 million years before present.

These fossil lichens differ from the Scottish lichens not just in age, Taylor said. They also occupied different environmental niches. The Scottish lichens were land dwellers, Taylor said, while the Chinese fossils came from the sea.

Most people think of lichens as a single organism. Actually, though, a lichen is a collaboration of organisms - two, three or more - working together to survive in a harsh environment. One or more collaborators - a cyanobacterium (or blue-green alga), a green alga or both, for example - may produce food for the team from the same raw material, carbon dioxide, that other plants use.

The other organism, a fungus, provides nutrients, moisture and protection in the collaboration.
One question raised by the new finding, Taylor says, is the relationship between the land-dwelling lichens and the sea-dwellers. Although a fungus is important in a land situation because it provides moisture, in the marine environment, dehydration is not an issue.

Thus, says, Xiao, in a marine environment, "The alga and cyanobacteria are not obliged to live with the fungi."

So the researchers agree that the land-based and sea-based lichens may have evolved separately - or not.

" We know that this symbiotic relationship was forged 600 million years ago or earlier," Xiao says. "But was it carried over to land, or did each organism invade land independently, then begin to interact - independent of a previous relationship?

" If the latter, then the 600-million-year-old relationship may not be the direct ancestor of the 400-million-year-old relationship."

The teamwork so crucial to lichen life has doubtless re-evolved many times, the researchers say.

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