High-Altitude Extreme Environments Drive Convergent Evolution of Skin Microbiota in Humans and Horses

Unique skin microbial communities have been shaped by the harsh climatic conditions in high-altitude areas, such as intense ultraviolet radiation and low oxygen concentration. However, it is unknown whether high altitude contributes to shaping common microbiota inhabiting the skin across different mammals. The skin microbial communities of humans and horses living in high-altitude (Tibetan) and low-altitude areas were analyzed using full-length 16S rRNA sequencing technology. Alpha diversity differed between high- and low-altitude groups (p < 0.01). Skin microbial community composition also differed between high- and low-altitude areas (p < 0.05). Some of the common taxa present in the skin of humans and horses in high-altitude areas were identified as extreme microorganisms capable of adapting to the harsh high-altitude environment. Five bacterial taxa, including the genera Sphingomonas, Brevundimonas, and Kocuria, as well as the species Acinetobacter guillouiae and Arboricoccus pini, were significantly enriched (p < 0.01) on the skin of both humans and horses in high-altitude areas. Meanwhile, some taxa enriched on the skin surface at the same altitude showed preferences for mammalian species. Acinetobacter johnsonii, Anaerococcus nagyae, and Anaerococcus octavius were significantly enriched (p < 0.05) in the skin of humans at both high and low altitudes, whereas Acinetobacter pseudolwoffii and Armatimonas rosea, Archangium gephyra and Acinetobacter lwoffii were significantly enriched (p < 0.05) in the skin of horses at both high and low altitudes. In the network analyses, a positive correlation (p < 0.01) was shown between the skin taxa enriched in high-altitude areas and each other, while a negative correlation (p < 0.01) was found between the skin microorganisms enriched in high-altitude areas and those enriched in low-altitude areas. Overall, our findings indicate that high-altitude extreme environments drive convergent evolution of skin microbiota across mammals, reflecting the joint effects of environmental selection and host-related filtering on community assembly. This cross-species comparison provides a framework for understanding skin microbiome responses to extreme environments in plateau mammals.