Abstract
To gain insights into evolutionary forces that have shaped the history of Bornean and Sumatran populations of orang-utans, we compare patterns of variation across more than 11 million single nucleotide polymorphisms found by previous mitochondrial and autosomal genome sequencing of 10 wild-caught orang-utans. Our analysis of the mitochondrial data yields a far more ancient split time between the two populations (∼3.4 million years ago) than estimates based on autosomal data (0.4 million years ago), suggesting a complex speciation process with moderate levels of primarily male migration. We find that the distribution of selection coefficients consistent with the observed frequency spectrum of autosomal non-synonymous polymorphisms in orang-utans is similar to the distribution in humans. Our analysis indicates that 35% of genes have evolved under detectable negative selection. Overall, our findings suggest that purifying natural selection, genetic drift, and a complex demographic history are the dominant drivers of genome evolution for the two orang-utan populations.
Highlights
Pongo pygmaeus and Pongo abelii, Bornean and Sumatran orangutans, respectively, are arboreal Asian great apes whose distributions are exclusive to the islands of Borneo and Sumatra
Since mitochondrial DNA (mtDNA) is inherited solely from the mother, comparison of mtDNA-inferred demographic history to that inferred from autosomal DNA enables inference of sex-biased migration
The phylogenetic tree inferred from this combined dataset (Figure 1A) places our 10 individuals throughout the tree, which indicates that our samples are representative of this larger data set
Summary
Pongo pygmaeus and Pongo abelii, Bornean and Sumatran orangutans, respectively, are arboreal Asian great apes whose distributions are exclusive to the islands of Borneo and Sumatra. We aim to assess the role of competing evolutionary forces including natural selection, genetic drift, and migration in shaping genomewide patterns of variation cross 10 previously sequenced wild orang-utan genomes. Multiple factors have impacted the recent evolutionary history and current distributions of orang-utans, and it is important to understand these abiotic and biotic factors before turning to genome analysis. Three factors that are important for understanding orang-utan genome variation are the biogeography of the region over the last million years, the social structure of orang-utans, and the impact of humans on orang-utan populations. Recurring glacial periods led to a cooler, drier and more seasonal climate [1] and contracted rain forest likely isolated populations of orang-utans. Especially the Toba super-eruption, could have played a large role in patterning Sumatran orang-utan genome diversity as shown by Nater et al [7,8]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
