Summary: Despite their important roles in host nutrition, metabolism and adaptability, the knowledge on how the mammalian gut microbial community assemble is relatively scanty, especially regarding the ecological mechanisms that govern microbiota along environmental gradients. To address this, we surveyed the diversity, function and ecological processes of gut microbiota in the wild plateau pika, Ochotona curzoniae , along the elevational gradient from 3106 to 4331 m on ‘the Roof of the World’—Qinghai‐Tibet Plateau. The results indicated that the alpha, beta and functional diversity of gut microbiota significantly increased with elevation, and elevation significantly explained the variations in the gut microbial communities, even after controlling for geographical distance, host sex and body weight. Some 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 the relative contributions of environmental filtering responsible for local gut communities increased with elevation. In addition, deterministic processes dominated gut microbial communities in the high‐altitude (more than 3694 m) pikas, while the percentages of stochastic and deterministic processes were very close in the low‐altitude (3106 and 3580 m) pikas. The observed mechanisms that influence pika gut microbiota assembly and function seemed to be mainly mediated by the internal gut environment and by the external environmental pressure (i.e. lower temperature) in the harsh high‐altitude environment. These findings enhance our understanding of gut microbiota assembly patterns and function in wild mammals from extreme harsh environments.

The Tibetan Plateau is a unique, biodiverse ecosystem with an important role in the climate and hydrological system of Asia. Its vegetation supports important functions including fodder provision, erosion prevention and water retention. Assessing vegetation trends of the Tibetan Plateau is crucial to understand effects of recent climate and land-use changes. Most existing vegetation trend products covering the entire Tibetan Plateau have a coarse spatial grain and cover short temporal ranges. This hampers their applicability in studies conducted at local scales where land-use decisions take place and at time scales where climate changes become apparent. Here, we present vegetation trend products for the entire Tibetan Plateau at a spatial resolution of 30 m for the time period 1990–2018. These products include results of a modified Mann-Kendall trend test applied to annual Landsat-based NDVI mosaics, composed from all satellite observations acquired during the vegetation periods as well as NDVI difference images. These data can be valuable to many researchers including for example wildlife ecologists, rangeland experts and climate change researchers.

The rumen microbiota plays an important role in animal functional attributes. These microbes are indispensable for the normal physiological development of the rumen, and may also convert the plant polysaccharides from grass into available milk and meat, making it highly valuable to humans. Exploring the microbial composition and metabolites of rumen across developmental stages is important for understanding ruminant nutrition and metabolism. However, relatively few reports have investigated the microbiome and metabolites across developmental stages in ruminants. Using 16S rRNA gene sequnecing, metabolomics and high-performance liquid chromatography techniques, we compared the rumen microbiota, metabolites and short chain fatty acids (SCFAs) between lambs and sub-adult Tibetan sheep (Ovis aries) from Qinghai-Tibetan Plateau. Bacteroidetes and Spirochaetae were enriched in sub-adult sheep, while Firmicutes and Tenericutes were more abundant in young individuals. The sub-adult individuals had higher alpha diversity values than those in young sheep. Metabolomics analysis showed that the content of essential amino acids and related gene functional pathways in rumen were different between the lambs and sub-adult population. L-Leucine that participates in valine, leucine and isoleucine biosynthesis was more abundant in the lambs, while phenylethylamine that takes part in phenylalanine metabolism was more enriched in the sub-adults. Both rumen microbial community structures and metabolite profiles were impacted by age, but rumen SCFA concentration was relatively stable between different age stages. Some specific microbes (e.g., Clostridium and Ruminococcaceae) were positively associated with L-Leucine but negatively correlated with phenylethylamine, implying that rumen microbes may play different roles for metabolite production at different ages. Mantel test analysis showed that rumen microbiota was significantly correlated with metabolomics and SCFA profiles. Our results indicates the close relationship between microbial composition and metabolites, and also reveal different nutritional requirement for different ages in ruminants, thus having important significance for regulating animal nutrition and metabolism by microbiome intervention.

Human skin microbiota plays a crucial role in the defense against pathogens, and is associated with various skin diseases. High elevation is positively correlated with various extreme environmental conditions (i.e., high ultraviolet radiation), which may exert selection pressure on skin microbiota, and therefore influence human health. Most studies regarding skin microbial communities have focused on low-elevation hosts. Few studies have explored skin microbiota in high-elevation humans. Here, we investigated the diversity, function, assembly, and co-occurrence patterns of skin microbiotas from 35 health human subjects across three body sites (forehead, opisthenar, and palm) and seven elevation gradients from 501 to 3431 m. Alpha diversity values (i.e., Shannon diversity and observed operational taxonomic units (OTUs)) decreased with increasing elevation regardless of the body site, while beta diversity (Jaccard and Bray–Curtis dissimilarities) showed an increasing trend with elevation. Elevation is a significant factor that influences human skin microbiota, even after controlling host-related factors. Skin microbiotas at high elevation with more than 3000 m on the Qinghai–Tibet Plateau, had a significant structural or functional separation from those at low elevation with less than 3000 m. Notably, the clustering coefficient, average degree, and network density were all lower at high-elevation than those at low-elevation, suggesting that high-elevation skin networks were more fragile and less connected. Phylogenetic analysis showed that human skin microbiotas are mainly dominated by stochastic processes (58.4%–74.6%), but skin microbiotas at high-elevation harbor a greater portion of deterministic processes than those at low-elevation, indicating that high-elevation may be conducive to the promotion of deterministic processes. Our results reveal that the filtering and selection of the changeable high-elevation environment on the Qinghai–Tibet Plateau may lead to less stable skin microbial community structures.

According to life history theory, animals living in extreme environments have evolved specific behavioral and physiological strategies for survival. However, the genetic mechanisms underpinning these strategies are unclear. As the highest geographical unit on Earth, the Qinghai–Tibet Plateau is characterized by an extreme environment and climate. During long-term evolutionary processes, animals that inhabit the plateau have evolved specialized morphological and physiological traits. The plateau pika (Ochotona curzoniae), one of the native small mammals that evolved on the Qinghai–Tibet Plateau, has adapted well to this cold and hypoxic environment. To explore the genetic mechanisms underlying the physiological adaptations of plateau pika to extremely cold ambient temperatures, we measured the differences in resting metabolic rate (RMR) and metabolism-related gene expression in individuals inhabiting three distinct altitudes (i.e., 3,321, 3,663, and 4,194 m). Results showed that the body mass and RMR of plateau pika at high- and medium-altitudes were significantly higher than those at the low-altitude. The expression levels of peroxisome proliferator-activated receptor α (pparα), peroxisome proliferator-activated receptor-γ coactivator-1α (pgc-1α), and the PR domain-containing 16 (PRDM16) in white (WAT) and brown (BAT) adipose tissues of plateau pika from high- and medium-altitudes were significantly higher than in pika from the low-altitude region. The enhanced expression levels of pgc-1α and pparα genes in the WAT of pika at high-altitude showed that WAT underwent “browning” and increased thermogenic properties. An increase in the expression of uncoupling protein 1 (UCP1) in the BAT of pika at high altitude indicated that BAT increased their thermogenic properties. The gene expression levels of pparα and pgc-1α in skeletal muscles were significantly higher in high-altitude pika. Simultaneously, the expression of the sarcolipin (SLN) gene in skeletal muscles significantly increased in high-altitude pika. Our results suggest that plateau pika adapted to an extremely cold environment via browning WAT, thereby activating BAT and enhancing SLN expression to increase non-shivering thermogenesis. This study demonstrates that plateau pika can increase thermogenic gene expression and energy metabolism to adapt to the extreme environments on the plateau.