Population genetics of Himalayan langurs and its taxonomic implications

Himalayan langurs ( Semnopithecus schistaceus ) are one of the most widely distributed colobine monkeys found in the Himalayas from Pakistan in the west to Bhutan in the east. Further, their distribution encompasses a wide range of elevation (from the foothills of the Himalayas to 4,270 m above sea level) and is interspersed with numerous deep river valleys. In this study, we investigate the role of riverine barriers and elevational gradients in shaping the population genetic structure in these langurs. Previous mitochondrial marker-based broad scale studies suggested limited role of river valleys in shaping the phylogeography of these langurs. Here we have utilized nuclear microsatellites and a more fine-scale sampling to further explore this issue. Fecal samples were non-invasively collected from two Indian Himalayan states Himachal Pradesh and Uttarakhand based on distribution records from past studies. A total of 7 microsatellite markers were genotyped for these samples. The data were subjected to various analyses, including Neighbor-joining tree, PCoA, AMOVA, STRUCTURE, and paired Mantel test. The results show an overall lack of population genetic structure and a much higher geneflow along elevational gradient than across river valleys. Significant isolation by distance was also observed. Additionally, our results do not support splitting the Himalayan langurs into multiple species/subspecies based on elevational gradient.