Historical genomes reveal recent changes in genetic health of eastern gorillas

December 27, 2018, Uppsala University

Historical collections of eastern gorilla specimens spanning the last 100 years were used to provide a glimpse into the recent past of this critically endangered species. Credit: Katerina Guschanski

The critically endangered Grauer's gorilla has recently lost genetic diversity and has experienced an increase in harmful mutations. These conclusions were reached by an international team of researchers who sequenced eleven genomes from eastern gorilla specimens collected up to 100 years ago, and compared these with genomes from present-day individuals. The results are now published in Current Biology.

Many wild animals have declined in numbers over the past century, and scientists have long worried that these declines have resulted in losses of genetic diversity, increased inbreeding and an accumulation of harmful mutations. Although this could lead to an even higher risk of extinction in threatened species, investigating recent changes in genetic viability has been difficult. In a new study, a team led by scientists from Uppsala University and the Swedish Museum of Natural History has used specimens stored in museum collections to analyse changes in eastern gorilla genomes over the past 100 years.

"We found that the genetic diversity in Grauer's gorilla has declined significantly in just a few generations," says Tom van der Valk, a Ph.D. student at Uppsala University in Sweden.

Grauer's gorillas are found in the Democratic Republic of the Congo and have declined by 80 per cent in recent decades due to poaching and habitat destruction. The results from the comparison of historical and modern genomes show that this decline has led to increased inbreeding and a loss of genetic variation. This in turn means that Grauer's gorillas have likely become less able to adapt to future disease outbreaks and changes in their environment. In addition, the scientists identified several mutations that are probably harmful and that have increased in frequency over the past four to five generations as a consequence of the decline in population size. In the closely related mountain gorilla, however, the scientists did not discover any significant genetic changes, suggesting that its genetic viability has remained stable over the past 100 years.

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