"The most lasting finding of our study may be the discovery of ancient geographic variation within widespread species, indicating that many rain forest tree species were widely distributed before the major uplift of the northern Andes," said co-author Eldredge Bermingham of the Smithsonian Tropical Research Institute.
To determine the age of each tree species, the researchers extracted and sequenced DNA from plant samples, then looked at the number of genetic mutations contained in those sequences. Using a molecular clock approach and population genetic models, they estimated how long it would take for each of the tree populations to accumulate the observed number of mutations, which provided a minimum age for each species.
"An important caveat is that because we've been in a cold period over the past 2 million years basically the whole Quaternary Period some of the trees' adaptations to warmth tolerance may have been lost," Dick said. "Additional research is needed to test whether this has occurred."
|Contact: Jim Erickson|
University of Michigan