The population of mountain gorillas living in the Virunga mountain range on the borders of the Democratic Republic of Congo, Rwanda, and Uganda, dropped significantly to 253 in 1981 due to excessive hunting and destruction of their habitat, and there was worry they would become extinct within a few decades. Stakeholders then made conservation efforts headed by various conservation organizations including the Gorilla Doctors, the Rwanda Development Board, and tourists interested in seeing the gorillas: and these efforts have bolstered the gorilla numbers in the area to 480.
Researchers have always worried about how such a small gene pool could affect the gorillas and decided to carry out a study of the consequences of such a small breeding circle. They have found out that most harmful genetic variations have been completely removed from the population as a result of inbreeding and that the mountain gorillas have adapted to surviving in such small populations.
According to Dr. Aylwyn Scally, who works with the Department of Genetics at University of Cambridge, this new information about demographic history and genetic diversity among the Virunga gorilla populations has given valuable information on how humans, apes, and their cousins adapt genetically to living in small populations.
The scientists fully analyzed blood samples of seven mountain gorillas to sequence their whole genomes.
The study also revealed that the Virunga mountain gorillas and the eastern lowland gorillas have a genetic diversity a third to half that of the Central and West Africa gorillas that live in large groups. While the low genetic diversity among the mountain gorillas is believed to increase vulnerability to disease and environmental change, it has several genetic benefits. Furthermore, there were fewer ‘loss-of-function’ variants in the Virunga gorilla populations than in west and central Africa gorilla populations: the variants are known to impair gene function and, at times, cause undesirable health conditions.
After analyzing the variations in each respective genome, researchers also made another discovery: the mountain gorillas have lived in small groups for several millennia. The researchers also used recently-developed methods to determine changes in the mountain gorilla population over the past few years and found out that the average population of mountain gorillas has remained in the hundreds for several thousand years, which is contrary to common belief.
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