Bonobos may be more vulnerable than previously thought, suggests genetics study

The three groups of bonobos have been living separately in different regions in Central Africa for tens of thousands of years, according to the study published in Current Biology by an international research team co-led by UCL, University of Vienna, and Max Planck Institute for Evolutionary Anthropology scientists.

Using genetic tests, the researchers confirmed previous evidence suggesting that there are three distinct groups of bonobos, originating in central, western, and far-western regions of the bonobo range. By quantifying the differences between these groups, the research team found that they can be as different from one another as the most closely-related chimpanzee subspecies.

Bonobos, commonly seen as the peace-loving primate, are, together with chimpanzees, the closest living relatives to humans as our genomes differ from theirs in only 1% of genetic bases.

The bonobo is endangered, with about 20,000 individuals alive in the wild, and are the most understudied great ape as they live exclusively in the Congo Basin of the Democratic Republic of the Congo, where social unrest has constrained research activities.

Joint first author Dr Sojung Han (University of Vienna, Austria, and Institut de Biologia Evolutiva, Spain) said: "Bonobos are a fascinating species, very closely related to humans, with unique patterns of social behaviour. They live in tight social groups which, despite some conflicts, are markedly peaceful and egalitarian. Interestingly, males stay in their birth social group while females migrate across groups, but females still form close alliances and can have higher dominance than males."

The research team analysed the genomic data of 30 bonobos born in the wild but now living in captivity. They sequenced the exomes (the protein-coding part of the genome) of 20 individuals living in an African sanctuary and analysed the full genomes of 10 other bonobos. While they could not always be certain what region of the Congo basin each bonobo had originated in, the researchers cross-referenced their dataset with previously published mitochondrial DNA data collected from 136 wild bonobos to paint a fuller picture of genetic diversity across the animal's range.

The researchers estimated that the central group diverged from the other two groups 145,000 years ago, with the two western groups diverging 60,000 years ago, with little mixing between the groups ever since.

Lead author Professor Aida Andrés (UCL Genetics Institute) said: "Bonobos may be even more vulnerable than previously thought, as their population actually consists of at least three smaller populations, some of which may historically have been amongst the smallest across similar primates.

"In order to survive, every species needs sufficient genetic diversity to adapt to a changing environment, and for bonobos, losing one of these three groups would be a devastating loss to the total genetic diversity of the species. It is vital that all three groups of bonobos are conserved in order to protect this fascinating and charismatic species."

The researchers say the differences between the bonobo groups should be further studied and considered in conservation efforts when planning efforts such as habitat preservation, translocations or potential reintroductions in case individuals are adapted to specific environments.

Dr Sojung Han said: "Unlike modern humans, who are spread all over the world, bonobos are limited to the Congo basin, but our work shows that there are indeed genetic differences between groups. This is exciting, and it will be very interesting to study, in the future, if there are any differential adaptations among these groups."

Joint first author Dr Cesare de Filippo (Max Planck Institute for Evolutionary Anthropology, Germany) said: "This work demonstrates how studying the genomes of endangered species can help better understand their populations and eventually aid conservation efforts. Even the genomes of captive individuals can help us, sometimes, understand their wild populations. Our findings show he vulnerability of bonobos as an endangered species, and stress the need to protect their environment to ensure their conservation."

The research was supported by Wellcome and the Max Planck Society, and involved researchers based in the UK, Austria, Germany, Spain, Denmark, and Israel.