Characteristics comparative of gut microbiota in four small mammal species co-occurring in the Hengduan Mountains: differences in environmental adaptation strategies between alien and endemic species.

The composition of gut microbiota is jointly determined by the host's food habit, ecological niche, and genetic background, serving as a direct reflection of the host's adaptation to its environment and evolutionary pressures. To investigate the distinct adaptation mechanisms of four sympatric small mammal species in the Hengduan Mountains region, this study compared the environmental adaptation strategies of endemic and alien species. This study collected ten wild specimens each of the Eothenomys miletus, Eothenomys oliter, Tupaia belangeri, and Apodemus chevrieri from Yunlong County, Yunnan Province. Using 16SrRNA gene sequencing technology, we analyzed the gut microbial composition, abundance, and community structure across species, investigating the distinct gut microbial community characteristics between the endemic species (E. miletus and E. oliter) and the alien species (T. belangeri and A. chevrieri.). Results indicate: E. miletus and E. oliter possess complex and diverse gut microbial communities with plant-degrading functions. These communities with sparse interactions are capable of utilizing multiple plant sources for nutrition and exhibit strong resilience against environmental disturbances. In contrast, T. belangeri and A.chevrieri exhibit simple, specialized, yet tightly cooperative omnivorous gut microbial communities. While capable of utilizing diverse food resources within specific adaptive environments, they demonstrate extreme specificity in adaptation to particular habitats or survival strategies and are relatively sensitive to external disturbances. Furthermore, the E. miletus, widely distributed across the Hengduan Mountains, its gut bacterial community is dominated by stochastic processes. In contrast, the T. belangeri shows a positive correlation with various gut bacteria associated with omnivorous characteristics. The distinction between these two distinct environmental adaptation strategies is particularly pronounced. In summary, Among these four sympatric small mammal species in the Hengduan Mountains, the gut microbiota of endemic and alien species showed high similarity respectively and exhibited convergence.