Gorillas (genomes) in the mist

Mountain gorillas are an endangered great ape subspecies that number around 800 individuals, inhabiting mountain ranges in central Africa. They have been the subject of numerous field studies, but few genetic analyses have been carried out.
Xue et al. (2015) sequenced whole genomes from wild individuals. Unlike other great apes, mountain gorillas had not been previously studied on a genome-wide scale, despite severe population bottlenecks and reports of phenotypic indicators of inbreeding.

© worldwildlife.org

© worldwildlife.org

Recent declines in the mountain gorilla population have led to rather extensive inbreeding. Xue et al. found that chromosomes were typically homozygous over 1/3 of their length, much more than severely inbred human populations.
Concern has mounted about the survival of mountain gorillas, particularly with regard to human encroachment on their habitat. This is all the more troubling as high levels of inbreeding may render populations less resilient to environmental change and pathogens.

However, the origins of this condition [an increased burden of deleterious mutations and low genetic diversity stemming from several recent generations of inbreeding] extend far into their history, because both eastern subspecies have experience a long decline over tens of millennia.

Xue et al. point to the “unhappy resemblance” between the demographic histories of mountain and eastern lowland gorillas with those the histories inferred from Neandertals before they became extinct.
However, they do discuss the fact that Gorilla subspecies have survived for thousands of generations at very low population levels. They may have developed strategies to avoid inbreeding, such as natal dispersal.
Genomic resources will aid in conservation efforts and future research to aid in preventing mountain gorilla extinction.
Xue, Y et al. (2015) Mountain gorilla genomes reveal the impact of long-term population decline and inbreeding. Science 348 (6231): 242-245. doi: 10.1126/science.aaa3952

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