Spatiotemporal differences induced changes in the structure and function of the gut microbiota in an endangered ungulate.

The composition and function of animal gut microbiota are shaped by various factors, among which diet is one of the major factors. Diet is affected by seasonal shifts and geographical differences, which in turn impact the host's nutritional levels. To adapt to these environmental changes, the gut microbiome often produces matching responses. Understanding the relationships among the environment, diet, host and the gut microbiome is helpful for exploring the environmental adaptation of wildlife. Here, we chose wild sika deer (Cervus nippon), which is composed natural allopatric populations, to explore how the environment shapes the gut microbiome and affects the relationship between microbiota composition and function and the mutual adaptation of the seasonal living environment to seasonal dietary changes. To this purpose we used DNA metabarcoding, 16S RNA gene amplification sequencing, metagenomic shotgun sequencing and nutritional analyses to comprehensively examine the relationships among the forage plant, nutrient status and host gut microbiome. Our analyses showed spatiotemporal differences in diet between the Tiebu and Hunchun regions, which ultimately led to varying intakes of protein, cellulose, and soluble sugar. The microbiome composition and function showed unique characteristics in each group, and significant differences were detected at the gene level for the protein absorption and metabolism pathway, the carbohydrate metabolic absorption pathway, and cellulase enzyme function, which are related to nutrition. We also found differences in the pathogenic bacteria and resistance mechanisms genes of the gut microbiota in different groups. Our results showed that the gut microbiome of allopatric populations adapts to changes in food composition and nutrition in different seasons and areas to help the host cope with spatiotemporal changes in the living environment. At the same time, varying levels of human activity can have potential health impacts on wild animals.