NEW YORK (GenomeWeb) – An international research team sequenced the whole genomes of 38 snub-nosed monkeys (Rhinopithecus roxellana), and found evidence of genetic adaptations that help the monkeys live in higher altitudes and low genetic diversity within the overall population.
Snub-nosed monkeys are native to the mountain forest treetops of China, Myanmar, and Vietnam. Although they were once widespread across Asia, they are now considered endangered with fewer than 30,000 individuals left among the five living species: the golden snub-nosed monkey (R. roxellena), the grey snub-nosed monkey (R. brelichi), the black snub-nosed monkey (R. bieti), the Tonkin snub-nosed monkey (R. avunculus), and the Myanmar snub-nosed monkey (R. strykeri).
As they reported in Molecular Biology and Evolution yesterday, the researchers collected muscle and skin samples from 38 individual monkeys (26 golden, 3 gray, 1 Myanmar, and 8 black) who died from natural causes, and performed whole-genome sequencing for each sample on an Illumina HiSeq 2000 platform. They then analyzed the sequencing data and built phylogenetic trees.
In their paper, the researchers noted a "similar load of deleterious variation" in all four subspecies of snub-nosed monkey, and found that genomic diversity was lower across all the snub-nosed monkey subspecies than in other primates. The team hypothesized that this was "likely the result of historical bottlenecks caused by glacial and tectonic events in the Pleistocene era," which is "consistent with biogeographical and fossil information indicating that snub-nosed monkeys were once widely distributed throughout China and parts of South Asia but that currently all five endangered species are confined to isolated mountain forests."
The researchers also found evidence for positive selection in several genes that potentially facilitate an adaptive response for hypoxia in the black snub-nosed monkey, which are confined to high altitude forests at approximately 11,150 to 15,000 feet — the highest elevation habitat range of any primate species. The species have had to adapt to a habitat with reduced oxygen levels, food supply, and lower temperatures. However, the researchers caution that "it is difficult to distinguish natural selection from genetic drift on specific loci, including candidate genes listed in the present study."
The team added that this was the first study to profile the endangered primate species in great detail and believes the findings "highlights the value of genomic data in assessing genetic diversity, measuring the power of natural selection, and identifying local adaptations."