Bonobos are among our closest living relatives. The great apes, which only occur in the Congo, are threatened with extinction because their habitat is limited and the population is small. But not all bonobos are the same: the already small number of individuals consists of at least three genetically different groups, as anthropologists discovered using genetic analyzes. This divides the bonobos into even smaller and therefore more endangered populations and makes it more difficult to protect this species.
Bonobos (Pan paniscus) are extremely similar to humans: only one percent of our genes differ from each other. This means that great apes, along with chimpanzees (Pan troglodytes), are among our closest relatives. Bonobos are known, among other things, for their harmonious and peaceful nature, for their close relationships and for solving social conflicts in their groups through sex. The bonobos also cause a stir because, according to the International Union for Conservation of Nature (IUCN), they are threatened with extinction. They only occur in the Congo Basin in the Democratic Republic of Congo. It is estimated that around 20,000 individuals still live there in the wild. In order to protect them, however, it would be helpful to know their existence in more detail.
Genomic analyzes reveal three bonobo groups
A team led by Sojung Han from the University of Vienna has now investigated whether the still living bonobos are a single homogeneous species or different subspecies with an even smaller population. To do this, the researchers analyzed the genome of a total of 30 bonobo individuals from monitored reserves as well as the maternally inherited mitochondrial DNA of 136 wild specimens.
The anthropologists found that there are actually three groups of bonobos that are genetically distinct. “We were able to show that the differences between these populations can be as great as those between different subspecies of chimpanzees,” reports Han. “The data also shows that the different bonobo groups separated genetically from one another up to 145,000 years ago.” The newly identified bonobo types probably come from three different regions in the west and center of the Congo, whose areas were temporarily spatially isolated, as the comparisons showed. Han and her colleagues suspect that there may be other subgroups in eastern Congo.
Small populations are more vulnerable
In addition, the researchers were able to prove that the bonobo population also consisted of only around 23,000 individuals before it was split into three groups. Then as now, bonobos always lived in very small populations with only a few individuals. One of today’s genetic subgroups even consists of only around 3,000 animals. Bonobos are one of the great apes that form the smallest populations – “comparable only to mountain gorillas and Tapanuli orangutans with 2,200 and 2,500 group members respectively,” according to the team.
However, this makes them more susceptible to inbreeding, which reduces genetic diversity and can lead to reproductive problems. This means that the bonobos are even more at risk of extinction than previously thought. The team believes that future conservation measures aimed at preserving their species should take into account that these are three different groups. For example, the respective populations should be given sufficient living space.
Source: University of Vienna; Specialist article: Current Biology, doi: 10.1016/j.cub.2024.09.043