Washington (AFP) – Scientists have produced the first chimpanzee genetic map in the wild, providing detailed reconstructions of past migrations of endangered species, and a new tool to combat illegal trafficking.
The genome catalog, which includes 828 individuals from across their vast African group, can now be used to link abducted chimpanzees – or their meat and body parts – to their place of origin within 100 kilometres.
The results of the years-long research project were published in the journal Cell Genomics on Wednesday.
“If we can know the genetic diversity of this endangered species, and its past demographic history … that can help design a better protection plan,” first author Claudia Fonteseri of the Institute of Evolutionary Biology in Spain told AFP.
DNA samples were collected from thousands of chimpanzee droppings as part of a pan-African program at 48 sites across Central and West Africa.
Stool sampling is a useful method for studying endangered species because it allows for extensive collection with minimal animal intervention.
But it also poses technical challenges because it contains only trace amounts of host DNA.
To get around these limitations, the team applied a new DNA sequencing technique called “target capture” which was first used to study Neanderthals whose remains decayed over thousands of years.
This allowed them to discover 50 percent more variants on a particular chromosome – number 21 – than had been found previously, and from this inferred previous gene flow between chimpanzee groups, bridging gaps in scientific understanding.
Previously, only 59 complete genomes of chimpanzees were sequenced, mainly from captive animals with limited information about their origin.
Just like humans, chimpanzees have a complex migration history, and the new research has allowed scientists to go back in time over the past 100,000 years with a new level of detail.
“There has been a lot of debate about whether the four lineages of chimpanzees really diverged from each other or whether there was a continuous gene flow between them,” co-author Mimi Arangelovic of the Max Planck Institute for Evolutionary Anthropology told AFP.
“We’ve been able to show, using different methods of analysis that look at very ancient and modern variations, that history is complex, much like the history of our species.”
The team knew that chimpanzee lineages were separated in the past, but that they also experienced periods of genetic exchange – which helps explain why previous studies that have attempted to reconstruct chimpanzees’ evolutionary history have come to different conclusions.
They found geographic barriers such as lakes and rivers that also created genetic barriers between subspecies as well as between communities, and they discovered new insights into the periods when chimpanzees interbred with bonobos.
Importantly, Arangelovich said, they confirmed a high level of contact among western chimpanzees, underscoring the need to maintain links between forests across West Africa.
Fontseri explained that the genetic map could help determine where the illegally trafficked chimpanzees came from.
Although reintroducing chimpanzees to the wild is a risky task due to the animals’ complex social structure, research has shown that they work best when placed in a reserve near their place of origin.
“Law enforcement can help to look at the most likely routes, and we can track them down,” Fontseri said.
They then hope to improve the genetic map with more samples and, having demonstrated that DNA in stool is a viable option, expand its use to study other primates.
© 2022 AFP