Ancient genomes reveal changes in the genetic status of oriental gorillas

Grauer's gorilla, severely threatened with extinction, has recently lost its genetic diversity and has experienced an increase in the number of harmful mutations. These findings were obtained by an international team of researchers that sequenced eleven genomes from eastern gorilla specimens collected up to 100 years ago and compared them with the genomes of current individuals. The results are now published in Current biology.

The number of wild animals has decreased in number over the last century and scientists have long been concerned that these declines have resulted in loss of genetic diversity, increased inbreeding and an accumulation of mutations. harmful. Although this may lead to an even greater risk of extinction in endangered species, it has been difficult to investigate recent changes in genetic viability. In a new study, a team led by scientists from the University of Uppsala and the Swedish Museum of Natural History used specimens stored in museum collections to badyze the evolution of the genome of the eastern gorilla over the last 100 years.

"We found that genetic diversity in Grauer's gorilla had dropped significantly in just a few generations," says Tom van der Valk, PhD student at the University of Uppsala in Sweden.

Grauer's gorillas are found in the Democratic Republic of Congo and have declined by 80% in recent decades due to poaching and destruction of their habitats. The results of the comparison of historical and modern genomes show that this decline has resulted in an increase in inbreeding and a loss of genetic variation. This means that Grauer's gorillas have probably become less able to adapt to future outbreaks and changes in their environment. In addition, scientists have identified several potentially harmful mutations that have increased in frequency over the last 4-5 generations as a result of declining population size. However, scientists have not found any significant genetic changes in mountain gorillas, suggesting that their genetic viability has remained stable over the past 100 years.

"This recent increase in the number of harmful mutations really underscores the need to reverse the decline of the Grauer gorilla population," said Dalen Love at the Swedish Museum of Natural History.

Some of the potentially harmful mutations whose frequency has increased have been discovered in genes that affect disease resistance and male fertility. In addition, researchers have identified mutations leading to loss of function of genes badociated with finger and toe development, which probably explains why current gorillas sometimes have fused fingers.

"Our study emphasizes that historical museum specimens provide a unique resource for monitoring recent changes in the genetic status of endangered species," said Katerina Guschanski of Uppsala University.

Interestingly, the reason that Grauer's gorillas have been more severely affected than mountain gorillas can be attributed to their deeper history. While Grauer's gorillas have experienced a large increase in numbers between 5,000 and 10,000 years ago, mountain gorillas have been rare for several thousand years. This small size of the long-term population may have allowed natural selection to suppress harmful mutations before the beginning of the decline in the number of mountain gorillas in the twentieth century.