Gut microbiota assembly of pika across elevations

Despite their important roles in host nutrition and metabolism, the knowledge on how the mammalian gut microbial communities assemble is still relatively scanty, especially regarding the ecological mechanisms that govern microbiota along environmental gradients. To address this, we surveyed the diversity, function and assembly of gut microbiota in the plateau pika, Ochotona curzoniae, along the elevational gradient from 3106 to 4331m on “the Roof of the World”—Qinghai-Tibet Plateau. The results indicate that both the alpha, beta and functional diversity of gut microbiota significantly increase with elevation, and elevation significantly explained the variations in the gut microbial communities, even after controlling for geographical distance, host sex and body weight. Most gene functions (e.g., nitrogen metabolism and protein kinases) associated with metabolism were enriched in the high-altitude pikas. Null model and phylogenetic analysis suggest that deterministic processes governed the assembly of gut microbial communities in the pikas. In addition, the relative contributions of deterministic processes responsible for local gut communities increased with elevation. The observed mechanisms that influence pika gut microbiota assembly seemed to be mainly mediated by the internal gut environment and by the external environmental pressure (i.e., lower temperature and more simplified diet resources) in the harsh high-altitude environment. These findings greatly enhance our understanding of gut microbiota assembly patterns in mammals, and also provide new insights into adaptation mechanisms of animals for extreme environments.