Mountain Gorillas Reveal Their Genetic Secrets | Genetics | Sci-News.com
9 April 2015
A team of genetic scientists, co-led by Dr Chris Tyler-Smith of the Wellcome Trust Sanger Institute and Dr Aylwyn Scally of the University of Cambridge, UK, has sequenced the whole genome of the mountain gorilla (Gorilla beringei beringei) and compared it with the genomes of three other Gorilla subspecies – the western lowland gorilla (G. gorilla gorilla), the Cross River gorilla (G. g. diehli), and the eastern lowland gorilla (G. b. graueri).
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The number of mountain gorillas living in the Virunga volcanic mountain range plummeted to approximately 253 in 1981 as a result of habitat destruction and hunting. Since then, conservation efforts have bolstered numbers to approximately 480 among the Virunga population.
“Mountain gorillas are among the most intensively studied primates in the wild, but this is the first in-depth, whole-genome analysis,” said Dr Tyler-Smith, a co-author of the paper published in the journal Science.
“Three years on from sequencing the gorilla reference genome, we can now compare the genomes of all gorilla populations, including the critically endangered mountain gorilla, and begin to understand their similarities and differences, and the genetic impact of inbreeding.”
Dr Tyler-Smith and his colleagues 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 are genetically adapting to surviving in small populations.
“This new understanding of genetic diversity and demographic history among gorilla populations provides us with valuable insight into how apes and humans, their closely related cousins, adapt genetically to living in small populations,” Dr Scally said.
“In these data we can observe the process by which genomes are purged of severely deleterious mutations by a small population size.”
Using blood samples collected over several years, the team was able to sequence the whole genomes of seven mountain gorillas.
The scientists could now see that these mountain gorillas, along with eastern lowland gorillas, were two to three times less genetically diverse than gorillas from larger groups in western regions of central Africa.
While there are concerns that this low level of genetic diversity may make the mountain gorillas more vulnerable to environmental change and to disease, including cross-infectious strains of human viruses, the inbreeding has, in some ways, been genetically beneficial.
Fewer harmful loss-of-function variants were found in the mountain gorilla population than in the more numerous western gorilla populations.
These variants stop genes from working and can cause serious, often fatal, health conditions.
By analyzing the variations in each genome, the scientists also discovered that mountain gorillas have survived in small numbers for thousands of years.
Using recently-developed methods, they were able to determine how the size of the population has changed over the past million years.
According to the study, the average population of mountain gorillas has numbered in the hundreds for many thousands of years; far longer than previously thought.