The largest study to date of genetic variation among chimpanzees has found that the traditional, geography-based sorting of chimps into three populationswestern, central and easternis underpinned by significant genetic differences, two to three times greater than the variation between the most different human populations.
In the April 2007 issue of the journal PLOS Genetics, researchers from the University of Chicago, Harvard, the Broad Institute and Arizona State show that there has been very little detectable admixture between the different populations and that chimps from the central and eastern populations are more closely related to each other than they are to the western "subspecies."
They also devised a simplified set of about 30 DNA markers that zookeepers or primatologists could use to determine the origins of a chimpanzee with uncertain heritage.
"Finding such a marked difference between the three groups has important implications for conservation," said Molly Przeworski, PhD, assistant professor of human genetics at the University of Chicago and a senior author of the study. "It means we have to protect three separate habitats, all threatened, instead of just one."
To unravel the evolutionary history to chimpanzees, the research team collected DNA from 78 common chimpanzees and six bonobos, a separate species of chimpanzee, and examined 310 DNA markers from each.
They found four "discontinuous populations," three of common chimps plus the bonobos. Hybrids, those with at least five percent of their DNA from more than one common chimpanzee population were rare, with most of the hybrid chimps born in captivity.
"We saw little evidence of migration between groups in the wild," said Celine Becquet, first author of the paper and a graduate student in Przeworski's laboratory. "Part of that could stem from the gaps in our samples, but we think most of this separation is genuine, a long-term conseq
Contact: John Easton
University of Chicago Medical Center