Scientists produce genetic map of chimpanzees to fight trafficking

Scientists have produced the first genetic map of chimpanzees in the wild, providing a detailed reconstruction of the endangered species’ past migrations, and a new tool to combat illegal trafficking.

The genomic catalog, which includes 828 individuals from across their vast African range, can now be used to link kidnapped chimpanzees – or their meat and parts of the body— to their place of origin within a radius of 100 kilometres.

The results of the year-long research project were published Wednesday in the journal Cell genomics.

Claudia Fontsere, first author from the Institute of Evolutionary Biology in Spain, told AFP: “If we can know the genetic diversity of this the threatened speciesand its past demographic history…this can help design a better conservation plan.”

DNA samples were collected from thousands of chimpanzee feces as part of the Pan-African program at 48 sites across West and Central Africa.

Fecal samples are a useful way to study endangered species because they allow extensive collection with minimal interference to animals.

But they also present technical challenges because they contain only traces of host DNA.

To overcome these constraints, the team applied a new DNA sequencing technique called “target capture” which was first used to study Neanderthals whose remains had been degraded for thousands of years.

This allowed them to discover 50% more variants on a particular chromosome – number 21 – than had been found before, and to infer past gene flow between chimpanzee populations, filling in the gaps in scientific understanding.

Previously, only 59 whole chimpanzee genomes had been sequenced, mostly from captive animals with limited information on their origin.

Complex migrations

Just like humans, chimpanzees have complex migration histories, and the new research has allowed scientists to look back over the past 100,000 years in a new level of detail.

“There has been a lot of debate about whether the four chimpanzee subspecies really diverged from each other or whether there was persistent gene flow between them,” Mimi told AFP. Arandjelovic, co-lead author from the Max Planck Institute for Evolutionary Anthropology.

“We were able to show, by using different methods of analysis that look at very old and more recent variations, that the story is complex, a bit like that of our own species.”

The team learned that chimpanzee subspecies were separated in the past, but also experienced periods of genetic exchange, which is why previous studies that attempted to reconstruct chimpanzees evolutionary history came to different conclusions.

They discovered that geographic barriers such as lakes and rivers also created genetic barriers between subspecies as well as between communities, and uncovered new information about when chimpanzees interbred with bonobos.

Importantly, they confirmed there was a high level of connectivity between western chimpanzees, highlighting the need to preserve connections between forests across West Africa, Arandjelovic said.

Fontsere said the genetic map could help determine where illegally trafficked chimpanzees came from.

Although reintroducing chimpanzees to the wild is a daunting task due to the animals’ complex social structure, research has shown that they do best when placed in a sanctuary near their place of origin.

“It can help law enforcement to look at the most likely routes, we can trace it,” Fontsere said.

They then hope to improve the genetic map with more samples and, after proving that fecal DNA is a viable option, expand its use to study other primates.

© 2022 AFP