Diet, nutrient characteristics and gut microbiome between summer and winter drive adaptive strategies of East China sika deer (Cervus nippon kopschi) in the Yangtze River basin.

Background: Adaptation of species represents the outcome of interactions between organisms and their environment, as well as a product of natural selection and evolution.

Method: To elucidate how East China sika deer in TNNR respond to seasonal climatic selection pressures in the mid-lower Yangtze River basin, we investigated their seasonal adaptive strategies via analyses of dietary nutrition and the gut microbiome, using high-throughput sequencing of the trnL P6-loop of chloroplast and 16S rRNA.

Results: In summer, sika deer consumed 174 plant species belonging to 183 genera and 107 families, exhibiting pronounced dietary generalization. Conversely, in winter, they fed on 130 species from 173 genera and 90 families, characterized by dietary specialization. The nutritional composition and availability of plants differed between the two seasons, driven by seasonal changes, which led to corresponding adjustments in foraging strategies. Notably, sika deer maintained a stable balance in nutrient intake across seasons. and industrialization of sika deer breeding in eastern China, whereas α-diversity was higher in winter. Microbiota in both seasons exhibited distinct correlations with consumed plant species and nutrients, but their microbial functions were predominantly enriched in metabolic processes. This pattern indicates that sika deer can flexibly reshape the structural and interaction networks of gut microbiota to enhance adaptive capacity to seasonal shifts. Overall, we demonstrated seasonal dynamics and provided new insights into understanding the diet diversity and nutrition components associated with gut microbiota in the adaptation of sika deer. These results will further facilitate genetic resource conservation, habitat improvement, food plant breeding, wild rescue, and industrialization of sika deer breeding in eastern China.