[LINK] On the recent inbreeding but continued survival of the mountain gorilla

[rfmcdonald]

The Dragon's Tales linked recently to the online paper "Mountain gorilla genomes reveal the impact of long-term population decline and inbreeding". The abstract is below.

Mountain gorillas are an endangered great ape subspecies and a prominent focus for conservation, yet we know little about their genomic diversity and evolutionary past. We sequenced whole genomes from multiple wild individuals and compared the genomes of all four Gorilla subspecies. We found that the two eastern subspecies have experienced a prolonged population decline over the past 100,000 years, resulting in very low genetic diversity and an increased overall burden of deleterious variation. A further recent decline in the mountain gorilla population has led to extensive inbreeding, such that individuals are typically homozygous at 34% of their sequence, leading to the purging of severely deleterious recessive mutations from the population. We discuss the causes of their decline and the consequences for their future survival.

One commentary suggests the extended survival of the mountain gorilla as a small population over millennia augurs well for the species' survival in the near term.

By analysing the variations in each genome, researchers also discovered that mountain gorillas have survived in small numbers for thousands of years. Using recently-developed methods, researchers were able to determine how the size of the population has changed over the past million years. According to their calculations, the average population of mountain gorillas has numbered in the hundreds for many thousands of years; far longer than previously thought.

"We worried that the dramatic decline in the 1980s would be catastrophic for mountain gorillas in the long term, but our genetic analyses suggest that gorillas have been coping with small population sizes for thousands of years," says Dr Yali Xue, first author from the Sanger Institute. "While comparable levels of inbreeding contributed to the extinction of our relatives the Neanderthals, mountain gorillas may be more resilient. There is no reason why they should not flourish for thousands of years to come."

It is hoped that the detailed, whole-genome sequence data gathered through this research will aid conservation efforts. Now that a genome-wide map of genetic differences between populations is available, it will be possible to identify the origins of gorillas that have been illegally captured or killed. This will enable more gorillas to be returned to the wild and will make it easier to bring prosecutions against those who poach gorillas for souvenirs and bush meat.

"Our dedicated programme of clinical monitoring and intervention in cooperation with the Rwanda Development Board, the Institut Congolese pour la Conservation du Nature and local communities is helping to ensure the health and sustainability of endangered mountain gorillas," says Dr Mike Cranfield, Co-Director of Gorilla Doctors. "Detailed genetic data help us trace where confiscated gorillas came from, and allows the assessment of the genetic health of the population as well as their susceptibility to certain health issues."