'Living fossil' tree contains genetic imprints of rain forests under clim...( ANN ARBOR Mich.---A living fossi...)

ANN ARBOR, Mich.---A "living fossil" tree species is helping a University of Michigan researcher understand how tropical forests responded to past climate change and how they may react to global warming in the future.

The research appears in the November issue of the journal Evolution.

Symphonia globulifera is a widespread tropical tree with a history that goes back some 45 million years in Africa, said Christopher Dick, an assistant professor of ecology and evolutionary biology who is lead author on the paper. It is unusual among tropical trees in having a well-studied fossil record, partly because the oil industry uses its distinctive pollen fossils as a stratigraphic tool.

About 15 to 18 million years ago, deposits of fossil pollen suggest, Symphonia suddenly appeared in South America and then in Central America. Unlike kapok, a tropical tree with a similar distribution that Dick also has studied, Symphonia isn't well-suited for traveling across the ocean---its seeds dry out easily and can't tolerate saltwater. So how did Symphonia reach the neotropics? Most likely the seeds hitched rides from Africa on rafts of vegetation, as monkeys did, Dick said. Even whole trunks, which can send out shoots when they reach a suitable resting place, may have made the journey. Because Central and South American had no land connection at the time, Symphonia must have colonized each location separately.

Once Symphonia reached its new home, it spread throughout the neotropical rain forests. By measuring genetic diversity between existing populations, Dick and coworker Myriam Heuertz of the Universit Libre de Bruxelles were able to reconstruct environmental histories of the areas Symphonia colonized.

"For Central America, we see a pattern in Symphonia that also has been found in a number of other species, with highly genetically differentiated populations across the landscape," Dick said. "We think the pattern is t
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