Evidence of tiger population structure and dispersal in the montane conservation landscape of Bhutan

Bhutan is a part of the second-largest Tiger Conservation Landscape (TCL), The Northern Forest Complex-Namdapha-Royal Manas, and is home to a tiger population of global conservation priority. With its well-connected protected area network and a vast expanse of forested landscape, Bhutan has a unique potential to spatially connect tiger populations in the Terai TCL of India and Nepal on the western side to the north-eastern part of the Indian subcontinent. However, information on genetic structure and connectivity among tiger populations is lacking in the Eastern Himalayan region. Due to the large and contiguous forested landscape with a network of well-connected protected areas and strong environmental protection measures in Bhutan, tiger populations in Bhutan are expected to have high genetic variation and gene flow. We made the first-ever attempt at the genetic sampling of the tiger population in Bhutan, where we genotyped 24 tiger individuals using thirteen microsatellite loci. Genetic analyses revealed three genetic clusters and found high expected heterozygosity (mean H_E = 0.73) and moderate-to-high genetic differentiation (F_ST = 0.135) within this pool of sampled tigers. We also were able to assign poached tigers to our inferred genetic clusters. Two individual wild tigers showed distinct multilocus genotypes, similar to each other but highly divergent from all other sampled tigers, suggesting their origin from outside the sampled areas. Our study provides the first insights into the population genetic structure of tigers in this important region and suggests that gene flow is less than suggested by dispersal. A larger landscape-level genetic study with implications for the transboundary conservation of tigers in this highly biodiverse landscape is warranted.