|Juvenile mountain gorillas, Photo credit: Philip Milne|
A paper by Xue and colleagues (2015) published in Science last week details the genetic consequences of prolonged population decline in eastern lowland and mountain gorillas. Completing a whole-genome sequence on this species has led to some fascinating and some surprisingly optimistic findings.
Xue and colleagues report homozygosity, or having two forms of the same gene that are identical, is higher in mountain and eastern lowland gorillas than in western lowland gorillas and even the most inbred populations of humans. Within the study populations, chromosomes were found to be homozygous on over one third of their total length, indicating that the parents of these individuals are related. The degree to which this homozygosity extends suggests that mountain gorillas have experienced several recent doses of inbreeding.
|Mountain gorilla adults and infant. Photo credit: Derek Keats|
The study also found that mountain gorillas have a lower rate of the harmful loss-of-function variants than do their more populous relatives, western lowland gorillas. Loss-of-function variants can be fatal. Mountain gorillas also appear to have survived at low population numbers for a long time, thousands of years. This is excellent news! Although it's certainly doesn't mean we should relinquish our conservation efforts. The authors of this study find further evidence to suggest that the last great environmental change (tropical forests to savannah) caused a collapse in mountain gorillas and western lowland gorillas.
While inbreeding usually makes for a risky situation as environmental changes or disease, for example, could wipe out substantial parts of a population, it seems mountain gorillas are doing better than expected. They are inbred but they're doing well.
Food for thought: How does this new study relate to gorilla conservation issues? How might a better understanding of population genetics help combat poaching and the illegal wildlife trade?
Links of interest:
IUCN Redlist overview of species
Gorilla Doctors Website
Paper, "Great ape genetic diversity and population history"
Xue, Y., Prado-Martinez, J., Sudmant, P. H., Narasimhan, V., Ayub, Q., Szpak, M., ... & Scally, A. (2015). Mountain gorilla genomes reveal the impact of long-term population decline and inbreeding. Science, 348(6231), 242-245.