‘Living fossil’ tree helping understand climate change effects

October 31st, 2008 - 11:02 am ICT by IANS  

Washington, Oct 31 (IANS) A tree that has been called a “living fossil” is helping researchers understand how tropical forests responded to past climate change and how they may react to future global warming.Symphonia globulifera is a tropical tree with a history going back 45 million years in Africa, said Christopher Dick, assistant professor of evolutionary biology, Michigan University.

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 travelling across the ocean - its seeds dry out easily and can’t tolerate saltwater, said a release of Michigan University.

So how did Symphonia reach the neotropics? Most likely the seeds hitched rides from Africa on rafts of vegetation, as monkeys did, Dick said in a new paper of which he is a co-author. The paper will appear in the November issue of the journal Evolution.

Even whole trunks, which can send out shoots when they reach a suitable resting place, may have made the journey. Because central and south America had no land connection at the time, Symphonia must have colonised 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 co-worker Myriam Heuertz of the Université Libre de Bruxelles were able to reconstruct environmental histories of the areas Symphonia colonised.

“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 the result of the distinctive forest history of Mesoamerica, which was relatively dry during the glacial period 10,000 years ago. In many places the forests were confined to hilltops or the wettest lowland regions. What we’re seeing in the patterns of genetic diversity is a signature of that forest history.”

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