The number of the critically endangered Grauer's gorilla has significantly shrank over the past several decades it led to loss of genetic diversity that now threatens the survival of the species.

Shrinking Population Size Led To Inbreeding

In a new study published in the journal Current Biology on Thursday, Love Dalén, from the Swedish Museum of Natural History, and colleagues sequenced the genomes of several eastern gorilla specimens collected a century ago.

They then compared the results to those of the living eastern gorilla, also known as the Grauer's gorillas, that live in the Democratic Republic of the Congo.

The findings showed the Grauer's gorillas have accumulated harmful mutations as the species' genetic diversity significantly declined in just a few generations.

The Grauer's gorilla population has declined by 80 percent over the last several decades because of poaching and habitat losses.

The shrinking number led to increased occurrence of inbreeding, as relatives are more likely to mate with a smaller population. This in turn resulted in loss of genetic diversity and harmful mutations.

Harmful Mutations

Dalén and colleagues identified several potentially harmful mutations that have increased in frequency over the past four to five generations of the Grauer's gorilla.

Some of these were found in genes that affect male fertility and disease resistance. These changes leave the species less capable of adapting to new diseases and shifting environments.

The researchers also identified mutations that lead to loss of functions in genes associated with finger and toe developments, which can explain why some Grauer's gorillas have fused digits.

Dalén and colleagues said that the findings highlight the need to address the plummeting population of the Grauer's Gorilla. There are less than 4,000 of the species today, and the Grauer's gorilla is now listed as critically endangered.

"This recent increase in harmful mutations really emphasises the need to reverse the ongoing population decline in Grauer's gorillas," Dalén said.

Other Species Also At Risk

The researchers also warned that there may be other species that may suffer from the same fate as a result of plummeting populations.

"Many species have experienced severe population declines in the last centuries and may thus face similar genomic consequences as reported here for Grauer's gorillas. In species with shorter generation time, such consequences may be even more severe due to faster genomic change," the researchers wrote in their study.