Scientists in Cameroon, the Netherlands, the United Kingdom and the United States have discovered that chimpanzee populations living in pretty close proximity are considerably more different genetically than are humans living on different continents. The study shows that genomics can play a key role in chimpanzee conservation. Presented in the journal PLoS Genetics, it was funded in part by the EUPRIM-NET ('European primate network: specialised infrastructures and procedures for biological and biomedical research') project, which clinched more than EUR 4.7 million under the Infrastructures Thematic area of the EU's Sixth Framework Programme (FP6). EUPRIM-NET allowed in particular the scientists to access samples available at the partner research infrastructures.
Scientists identified how common chimpanzees in equatorial Africa belong to one of three distinct populations, or subspecies: western, central and eastern chimpanzees. While researchers suggest a fourth group, the Cameroonian chimpanzee, lives in western Cameroon and southern Nigeria, some have started to question whether this constitutes a distinct group. Enter researchers in this latest study who analysed the deoxyribonucleic acid (DNA) from 54 chimpanzees, measuring the DNA at 818 positions across the genome that was different between individuals. The researchers found that Cameroonian chimpanzees are distinct from the other groups.
'These findings have important consequences for conservation,' says lead author Dr Rory Bowden of the University of Oxford. 'All great ape populations face unparalleled challenges from habitat loss, hunting and emerging infections, and conservation strategies need to be based on sound understanding of the underlying population structure. The fact that all four recognised populations of chimpanzees are genetically distinct emphasises the value of conserving them independently.
'Genomics can also provide tools for use in chimpanzee conservation. Genetic tests could cheaply and easily identify the population of origin of an individual chimpanzee or even a sample of bushmeat.'
Levels of genetic differentiation between the groups were compared with those based on similar data from humans from varied populations. The researchers discovered that although all the chimpanzee populations lived in relatively close proximity — a river separated the habitats of two groups — chimpanzees from different populations were considerably more different genetically than are humans living on different continents.
Commenting on the results, Professor Peter Donnelly, Director of the Wellcome Trust Centre for Human Genetics in Oxford and a senior author on the study, says: 'Relatively small numbers of humans left Africa 50 000 to 100 000 years ago. All non-African populations descended from them and are reasonably similar genetically. That chimpanzees from habitats in the same country, separated only by a river, are more distinct than humans from different continents is really interesting. It speaks to the great genetic similarities between human populations, and to much more stability, and less interbreeding, over hundreds of thousands of years, in the chimpanzee groups.'
The findings could help researchers develop a catalogue of genetic variation in order to identify genetically distinct groups and to produce easy and inexpensive tests of population of origin.
For his part, Dr Nick Mundy of the University of Cambridge, the other senior author, says: 'Because they are humans' nearest relatives, the structure and origins of chimpanzee populations have long been of wide interest. Future studies will be able to use genome data to uncover the adaptations that are unique to the Cameroonian chimpanzees.'