Seasonal Variation of Gut Bacterial Community in Wild Apodemus agrarius Is Associated With Intrinsic and Extrinsic Environments.

Environmental factors and the reproductive status of animals have been reported to influence host gut microbial community structure significantly. To date, there is a lack of integrated research reporting the relationships among environmental factors, gut microbial structure, and the life processes in animals. This study collected monthly temperature, precipitation, and vegetation indices in the sampling site, and body size metrics as well as reproductive indicators in wild Apodemus agrarius (Pallas, 1771) from 2016 to 2023; and also collected gut microbes in the monthly animal populations from March to December in 2023, and analyzed the relationships among climatic factors, gut microbiota structural features, body size, and reproductive indicators in the animal population. The results showed that both variations of monthly reproductive intensity and the α-diversity of gut bacterial community in A. agrarius population followed an "M"-shaped pattern over months. The mean monthly temperature, total precipitation, and mean monthly NDVI were significantly associated with α-diversity, reproductive intensity, and body size. The exploratory structural equation models suggested sex-specific associations among reproductive activity, gut bacterial alpha diversity, environmental factors, and host body size. The findings indicate correlated seasonal variation among environmental factors, gut microbial alpha diversity, and life-history traits in rodents.