Colobines are a unique group of Old World monkeys that principally eat leaves and seeds rather than fruits and insects. We report the sequencing at 146× coverage, de novo assembly and analyses of the genome of a male golden snub-nosed monkey (Rhinopithecus roxellana) and resequencing at 30× coverage of three related species (Rhinopithecus bieti, Rhinopithecus brelichi and Rhinopithecus strykeri). Comparative analyses showed that Asian colobines have an enhanced ability to derive energy from fatty acids and to degrade xenobiotics. We found evidence for functional evolution in the colobine RNASE1 gene, encoding a key secretory RNase that digests the high concentrations of bacterial RNA derived from symbiotic microflora. Demographic reconstructions indicated that the profile of ancient effective population sizes for R. roxellana more closely resembles that of giant panda rather than its congeners. These findings offer new insights into the dietary adaptations and evolutionary history of colobine primates.Knowledge of the patterns and processes underlying the evolution of alternative dietary strategies in nonhuman primates is critical to understanding hominin evolution, nutritional ecology and applications in biomedicine 1 . Colobines, a group of Old World monkeys, serve as an important model organism for studying the evolution of the primate diet because of their adaptation to folivory: they primarily eat leaves and seeds rather than fruits and insects as their major food source. In their specialized and compartmentalized stomachs, colobines allow symbiotic bacteria in the foregut to ferment structural carbohydrates and then recover nutrients by digesting the bacteria 2 . This strategy is similar to that used by other foregut fermenters found in an evolutionarily distantly related group of mammals (for example, artiodactyls). Although a number of primate genomes have been sequenced thus far, high-quality genome sequence information is absent for Asian and African colobines, a key group for elucidating the evolution and adaptation of primates as a whole. Snub-nosed monkeys (Rhinopithecus species) are a group of endangered colobines, which were once widely distributed in Asia but are now limited to mountain forests in China and Vietnam 3 (Supplementary Fig. 1).The golden snub-nosed monkey (GSM, R. roxellana) is recognized as an iconic endangered species in China for its golden coat, blue facial coloration, snub nose and specialized life history. Among its congeners, the black-white snub-nosed monkey (R. bieti), endemic to the Tibetan plateau, has the highest altitudinal distribution (>4,000 m above sea level) of any nonhuman primate. Given the above features and the fact that Rhinopithecus species consume difficult-to-digest foods that contain tannins (for example, leaves and pine seeds), we expected to identify genetic adaptations that enhance the breakdown of toxins, improve the regulation of energy metabolism and facilitate the digestion of symbiotic microbacteria. RESULTS Genomic sequences and the accumulation of...

The seasonal changes in home range and habitat use of the Sichuan snub-nosed monkey, Rhinopithecus roxellana, have been studied by radio tracking and direct observation in the Qinling Mountains of China. The home range size was 14.1 km² in spring, 9.5 km² in summer, 12.1 km² in autumn and 12.3 km² in winter; the total area used was 22.5 km². The area of the home range is closely correlated with the distribution and abundance of food resources. Seasonal change in the home range area is correlated with the phenology of the vegetation. An unusually large home range is a unique characteristic of this monkey.

Only a few primate species thrive in temperate regions characterized by relatively low temperature, low rainfall, low species diversity, high elevation, and especially an extended season of food scarcity during which they suffer from dietary stress. We present data of a case study of dietary strategies and fallback foods in snub-nosed monkeys (Rhinopithecus bieti) in the Samage Forest, Northwest Yunnan, PRC. The snub-nosed monkeys adjusted intake of plant food items corresponding with changes in the phenology of deciduous trees in the forest and specifically showed a strong preference for young leaves in spring. A non-plant food, lichens (Parmeliaceae), featured prominently in the diet throughout the year (annual representation in the diet was about 67%) and became the dominant food item in winter when palatable plant resources were scarce. Additional highly sought winter foods were frost-resistant fruits and winter buds of deciduous hardwoods. The snub-nosed monkeys' choice of lichens as a staple fallback food is likely because of their spatiotemporal consistency in occurrence, nutritional and energetic properties, and the ease with which they can be harvested. Using lichens is a way to mediate effects of seasonal dearth in palatable plant foods and ultimately a key survival strategy. The snub-nosed monkeys' fallback strategy affects various aspects of their biology, e.g., two- and three-dimensional range use and social organization. The higher abundance of lichens at higher altitudes explains the monkeys' tendency to occupy relatively high altitudes in winter despite the prevailing cold. As to social organization, the wide temporal and spatial availability of lichens strongly reduces the ecological costs of grouping, thus allowing for the formation of "super-groups." Usnea lichens, the snub-nosed monkeys' primary dietary component, are known to be highly susceptible to human-induced environmental changes such as air pollution, and a decline of this critical resource base could have devastating effects on the last remaining populations. Within the order Primates, lichenivory is a rare strategy and only found in a few species or populations inhabiting montane areas, i.e., Macaca sylvanus, Colobus angolensis, and Rhinopithecus roxellana. Other temperate-dwelling primates rely mainly on buds and bark as winter fallback foods.