Researchers have produced the first whole-genome sequences of endangered mountain gorillas in the Virunga volcanic mountain range in central Africa. Findings from sequence analysis suggest the gorillas have lived in small groups for thousands of years, coping well with inbreeding that scientists feared would lead to health problems. Based on these results, scientist say the gorillas, if properly protected from habitat destruction and hunting, should continue to flourish for thousands of years to come.
The study in the journal Science revealed a substantial loss of genetic diversity from inbreeding caused by mating with close relatives due to small population size. Inbreeding can increase threats from disease and environmental change by reducing the genetic ability to adapt and cause a larger hardship of harmful mutations.
“Mountain gorillas are critically endangered and at risk of extinction, and our study reveals that as well as suffering a dramatic collapse in numbers during the last century, they had already experienced a long decline going back many thousands of years, ” University of Cambridge geneticist Aylwyn Scally said.
The number of mountain gorillas living in the Virunga volcanic mountain range on the borders of Rwanda, Uganda and the Democratic Republic of Congo plummeted to approximately 253 in 1981 as a result of habitat destruction and hunting. Since then, conservation efforts led by the Rwanda Development Board and conservation organizations like the Gorilla Doctors (a partnership between the non-profit Mountain Gorilla Veterinary Project and the UC Davis Wildlife Health Center), and supported by tourists keen to see the gorillas made famous by late primatologist Dian Fossey, have bolstered numbers to approximately 480 among the Virunga population.
Researchers interested to learn how such a small gene pool would affect the mountain gorillas were surprised to find that many harmful genetic variations had been removed from the population through inbreeding, and that mountain gorillas genetically adapt to survive in small populations.
“We worried that the dramatic decline in the 1980s would be catastrophic for mountain gorillas in the long term, but our genetic analyses suggest that gorillas have been coping with small population sizes for thousands of years, ” says Dr Yali Xue, first author from the Sanger Institute. “While comparable levels of inbreeding contributed to the extinction of our relatives the Neanderthals, mountain gorillas may be more resilient. There is no reason why they should not flourish for thousands of years to come.”
It is hoped that the detailed, whole-genome sequence data gathered through this research will aid conservation efforts. Now that a genome-wide map of genetic differences between populations is available, it will be possible to identify the origins of gorillas that have been illegally captured or killed. This will enable more gorillas to be returned to the wild and will make it easier to bring prosecutions against those who poach gorillas for souvenirs and bush meat.